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Infectious Disease and Microbiology – Septic Bursitis
Bursitis refers to inflammation of a bursa, one of more than 150 sac-like structures in the body that cushion soft tissues over bony prominences. Bursitis may result from infection (pyogenic), crystal deposition due to trauma or gout, or inflammatory arthritis such as rheumatoid arthritis. Septic bursitis most commonly involves superficial bursae and frequently affects the olecranon, prepatellar, subdeltoid, ischial, and trochanteric bursae.
The most important predisposing factor for septic bursitis is trauma, which accounts for approximately 70% of cases. Repetitive microtrauma is common in certain activities and occupations. Specific associations include ischial bursitis in individuals with spinal cord injuries, malleolar bursitis in ice skaters, and subdeltoid bursitis following injections. Additional risk factors include diabetes mellitus, alcohol abuse, chronic skin conditions, intravenous drug use, and invasive procedures such as acupuncture or joint injections, which have been associated with outbreaks of methicillin-resistant Staphylococcus aureus (MRSA).
The most common causative organism is Staphylococcus aureus. Streptococcal species account for 5–30% of cases. Gram-negative bacteria and fungi are rare causes. Prototheca wickerhamii, an environmental algae, has been reported in immunocompromised individuals. In endemic regions, brucellosis should be considered in the differential diagnosis, and tuberculous bursitis may occur as part of disseminated disease.
Clinically, septic bursitis presents with localized painful swelling, erythema, warmth, and tenderness over the affected bursa. Fever may be present. Overlying cellulitis may extend beyond the bursa. Deep bursal infections are more likely to be associated with systemic signs of infection and bacteremia.
Aspiration of bursal fluid is the diagnostic procedure of choice. Fluid analysis typically shows elevated white blood cell counts, often below 20,000 cells/mm³ in septic bursitis. Gram stain positivity varies widely, and culture of aspirated fluid has high sensitivity and specificity. Use of liquid media may improve culture yield. Crystal analysis should be performed, as crystal-induced bursitis can coexist with infection. Laboratory blood tests may show inflammatory markers, but they are nonspecific.
Imaging may support the diagnosis. Plain radiographs can demonstrate soft tissue swelling and subcutaneous edema. Ultrasound is useful in identifying fluid collections and guiding aspiration. MRI may show a fluid-filled bursa with rim enhancement after gadolinium administration, while surrounding structures are typically spared unless there is extension of infection.
The differential diagnosis includes cellulitis, fasciitis, acute monoarthritis, gout, pseudogout, and traumatic injury.
Management includes repeated needle aspiration, often daily, until the bursa is no longer fluctuant. Empiric antibiotic therapy should cover staphylococci and streptococci. For methicillin-sensitive Staphylococcus aureus, intravenous oxacillin or nafcillin is recommended. For MRSA, vancomycin is indicated. Antibiotic therapy is generally continued for at least 14 days, although shorter courses (7 days) may be sufficient in selected non-immunocompromised patients with severe infection requiring hospitalization. The choice between intravenous and oral therapy depends on severity and systemic involvement. Immobilization of the affected joint is advised during acute treatment.
If medical therapy fails, or if there is persistent swelling, pain, or loculated infection, surgical incision and drainage may be necessary. In chronic or recurrent cases, excision of the bursa may be required.
Follow-up care includes rehabilitation to prevent limitation of joint movement and ensure restoration of function.
Bursitis refers to inflammation of a bursa, one of more than 150 sac-like structures in the body that cushion soft tissues over bony prominences. Bursitis may result from infection (pyogenic), crystal deposition due to trauma or gout, or inflammatory arthritis such as rheumatoid arthritis. Septic bursitis most commonly involves superficial bursae and frequently affects the olecranon, prepatellar, subdeltoid, ischial, and trochanteric bursae.
The most important predisposing factor for septic bursitis is trauma, which accounts for approximately 70% of cases. Repetitive microtrauma is common in certain activities and occupations. Specific associations include ischial bursitis in individuals with spinal cord injuries, malleolar bursitis in ice skaters, and subdeltoid bursitis following injections. Additional risk factors include diabetes mellitus, alcohol abuse, chronic skin conditions, intravenous drug use, and invasive procedures such as acupuncture or joint injections, which have been associated with outbreaks of methicillin-resistant Staphylococcus aureus (MRSA).
The most common causative organism is Staphylococcus aureus. Streptococcal species account for 5–30% of cases. Gram-negative bacteria and fungi are rare causes. Prototheca wickerhamii, an environmental algae, has been reported in immunocompromised individuals. In endemic regions, brucellosis should be considered in the differential diagnosis, and tuberculous bursitis may occur as part of disseminated disease.
Clinically, septic bursitis presents with localized painful swelling, erythema, warmth, and tenderness over the affected bursa. Fever may be present. Overlying cellulitis may extend beyond the bursa. Deep bursal infections are more likely to be associated with systemic signs of infection and bacteremia.
Aspiration of bursal fluid is the diagnostic procedure of choice. Fluid analysis typically shows elevated white blood cell counts, often below 20,000 cells/mm³ in septic bursitis. Gram stain positivity varies widely, and culture of aspirated fluid has high sensitivity and specificity. Use of liquid media may improve culture yield. Crystal analysis should be performed, as crystal-induced bursitis can coexist with infection. Laboratory blood tests may show inflammatory markers, but they are nonspecific.
Imaging may support the diagnosis. Plain radiographs can demonstrate soft tissue swelling and subcutaneous edema. Ultrasound is useful in identifying fluid collections and guiding aspiration. MRI may show a fluid-filled bursa with rim enhancement after gadolinium administration, while surrounding structures are typically spared unless there is extension of infection.
The differential diagnosis includes cellulitis, fasciitis, acute monoarthritis, gout, pseudogout, and traumatic injury.
Management includes repeated needle aspiration, often daily, until the bursa is no longer fluctuant. Empiric antibiotic therapy should cover staphylococci and streptococci. For methicillin-sensitive Staphylococcus aureus, intravenous oxacillin or nafcillin is recommended. For MRSA, vancomycin is indicated. Antibiotic therapy is generally continued for at least 14 days, although shorter courses (7 days) may be sufficient in selected non-immunocompromised patients with severe infection requiring hospitalization. The choice between intravenous and oral therapy depends on severity and systemic involvement. Immobilization of the affected joint is advised during acute treatment.
If medical therapy fails, or if there is persistent swelling, pain, or loculated infection, surgical incision and drainage may be necessary. In chronic or recurrent cases, excision of the bursa may be required.
Follow-up care includes rehabilitation to prevent limitation of joint movement and ensure restoration of function.
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Infectious Diseases and Microbiology: Trauma-Related Infections
Basics
Description
Trauma-related infections broadly include infections that arise directly or indirectly from wounds or injuries. A recently recognized high-risk group is patients needing emergency operations for non-trauma causes such as gastrointestinal perforation, obstruction, bleeding, or acute inflammation, which is associated with increased infection-related mortality.
Epidemiology
Incidence
Millions of wounds are treated annually in U.S. emergency departments, including large numbers of burns and lacerations, and cutting or piercing injuries generate substantial outpatient visits. Reported infection rates among trauma patients vary widely across studies. Sepsis contributes to a significant proportion of deaths in hospitalized trauma patients.
Risk Factors
Higher risk is linked to heavily contaminated wounds, impaired blood supply from injury, emergent splenectomy, glucocorticoid exposure, delayed treatment, obesity, and greater injury severity.
General Prevention
Thorough cleaning and irrigation with water or normal saline is essential. Topical antibiotics and occlusive dressings reduce infection rates in traumatic lacerations. Confirm tetanus immunization status and vaccinate patients who are overdue or uncertain. Highly contaminated wounds may require secondary intention healing or delayed primary closure. In open limb fractures, prophylactic antibiotics lower early infection risk. Although high-quality placebo-controlled trials are limited for severely injured contaminated patients, empiric antibiotics are commonly used for penetrating chest or abdominal injuries and severe head wounds. Short prophylactic courses are generally as effective as longer courses, supported by evidence in penetrating abdominal trauma showing no major outcome difference between 24-hour and 5-day regimens. Antibiotic levels can be altered by fluid shifts and hyperdynamic physiology, and data support higher doses for shorter durations, especially in trauma laparotomy patients. Short prophylaxis reduces infection in compound mandibular fractures. After traumatic splenectomy, the risk of early serious infection is low in isolated splenic injury but rises with greater injury and associated trauma; encapsulated organisms are key pathogens early and late. Administer pneumococcal and meningococcal vaccines once clinically stable after splenectomy. Strict infection control practices reduce hospital-acquired infections in severely injured patients.
Etiology
Trauma increases infection risk through vascular disruption and microcirculatory damage causing ischemia, edema, compartment syndromes, and necrosis; contamination of wounds and sterile spaces by soil or water exposure; post-shock immune dysfunction; reduced IgM responses after splenectomy compared with nonsplenectomized infected posttrauma patients; and additional immune suppression from corticosteroids used for head injury. Common infections in multiply injured patients include pneumonia and empyema, bacteremia or fungemia (including catheter-related), surgical site infection, intraabdominal infection, meningitis, urinary tract infection, sinus infection, wound infection, and Clostridioides difficile colitis after prior antibiotic exposure. Acinetobacter baumannii infections have been reported in injured military personnel from conflict regions, with some isolates susceptible only to carbapenems such as imipenem.
Diagnosis
History
Diagnosis is challenging because fever may be noninfectious after trauma, patients may be unable to provide history, examinations may be limited, and usual infection signs are less reliable in critically ill, multiply traumatized patients.
Physical Examination
Fever, tachycardia, and hypotension can occur after severe injury without infection. In critically ill patients, track ventilator requirements, sputum volume and character, and urine and stool output. In hospitalized trauma patients, perform a complete exam emphasizing indwelling devices, skin, operative wounds, abdomen, and respiratory findings. Inspect injured sites for local infection signs including pain, foul odor, erythema, swelling, purulent drainage, and delayed healing.
Diagnostic Tests and Interpretation
Laboratory Studies
Obtain CBC with differential, electrolytes, and kidney and liver function tests, recognizing leukocytosis may reflect trauma alone. Whenever possible, collect cultures from suspected sites before antibiotics, including blood, sputum, urine, cerebrospinal fluid studies and culture when penetrating head injury or CNS drains are present, wound cultures, and abscess cultures. With watery diarrhea and prior antibiotic exposure, test stool for C. difficile.
Imaging
Use chest radiography to assess pneumonia, especially in mechanically ventilated patients. Chest CT is more sensitive for thoracic infection in septic trauma patients and can guide correction of malpositioned or blocked thoracostomy tubes, though concurrent thoracic injuries can reduce test accuracy. Abdominal CT can identify intraabdominal infection such as perforation, colitis, cholecystitis, or abscess. For suspected extremity infection, ultrasound, CT, or MRI can help exclude abscess.
Diagnostic Procedures/Other
Image-guided or operative drainage of abscesses is diagnostic and therapeutic; send fluid for Gram stain, aerobic and anaerobic cultures, add fungal studies for abdominal or pelvic collections, and consider acid-fast bacilli smear and mycobacterial culture based on epidemiologic risk.
Differential Diagnosis
In severely injured patients, infection mimics include atelectasis, deep vein thrombosis, drug fever, allergic reactions or anaphylaxis, hypovolemia, large hematoma, sterile inflammation, pulmonary contusion, transfusion reactions, and central fever from brain injury.
Treatment
Medications
Correcting local anatomic problems such as open fractures or perforated abdominal organs is often more important than antibiotics alone. In trauma patients, unexplained hemodynamic instability not due to hypovolemia should prompt empiric antibiotics even if other infection signs are absent. Choose antibiotics based on suspected source, local resistance, trauma context (bites, water exposure, soil contamination), hospitalization duration and risk of resistant organisms, local MRSA prevalence, and allergies. If no source is identified, start broad-spectrum therapy including antistaphylococcal coverage plus broad gram-negative and anaerobic activity
.
Additional Treatment
Monitor clinical response and narrow therapy to culture and susceptibility results. If diagnostic evaluation is negative and the patient is stable, consider stopping antibiotics. Duration depends on infection site and clinical course. Remove central venous and urinary catheters as soon as they are no longer needed.
Issues for Referral
Severe injuries require urgent evaluation at experienced trauma centers with surgical and critical care capability. Infectious diseases consultation is useful when the patient is critically ill, not improving on therapy, or diagnosis remains uncertain.
Surgery/Other Procedures
Drain collections, debride necrotic tissue, and repair fractures or perforations promptly, and implement measures to mobilize respiratory secretions.
In-Patient Considerations
Initial Stabilization
Stabilize airway and circulation, provide rapid fluid resuscitation, and document all injuries.
Admission Criteria
Admit patients with penetrating injuries, fractures needing urgent repair, abnormal vital signs, impaired mental status, uncontrolled pain, or severe injuries. Burns meeting moderate to major thresholds require admission to specialized burn care centers.
Discharge Criteria
Discharge when fever has been absent for more than 24 hours, vital signs are stable, and follow-up for antibiotics and wound care is arranged.
Ongoing Care and Follow-Up
Patient Monitoring
Monitor closely for wound infection and healthcare-associated infections, which occur in a meaningful minority of hospitalized trauma patients.
Diet
Provide adequate nutritional support and consider nutrition consultation in severely injured hospitalized patients.
Patient Education
Teach warning signs of wound infection and provide clear instructions for wound care, including packing and dressing-change schedules.
Prognosis
Trauma-related infection increases mortality risk and is associated with worse functional outcomes during the year after injury compared with trauma patients without infection.
Complications
Serious outcomes include septic shock, respiratory failure, peritonitis and abdominal abscess, osteomyelitis, brain abscess, and acute acalculous cholecystitis.
Basics
Description
Trauma-related infections broadly include infections that arise directly or indirectly from wounds or injuries. A recently recognized high-risk group is patients needing emergency operations for non-trauma causes such as gastrointestinal perforation, obstruction, bleeding, or acute inflammation, which is associated with increased infection-related mortality.
Epidemiology
Incidence
Millions of wounds are treated annually in U.S. emergency departments, including large numbers of burns and lacerations, and cutting or piercing injuries generate substantial outpatient visits. Reported infection rates among trauma patients vary widely across studies. Sepsis contributes to a significant proportion of deaths in hospitalized trauma patients.
Risk Factors
Higher risk is linked to heavily contaminated wounds, impaired blood supply from injury, emergent splenectomy, glucocorticoid exposure, delayed treatment, obesity, and greater injury severity.
General Prevention
Thorough cleaning and irrigation with water or normal saline is essential. Topical antibiotics and occlusive dressings reduce infection rates in traumatic lacerations. Confirm tetanus immunization status and vaccinate patients who are overdue or uncertain. Highly contaminated wounds may require secondary intention healing or delayed primary closure. In open limb fractures, prophylactic antibiotics lower early infection risk. Although high-quality placebo-controlled trials are limited for severely injured contaminated patients, empiric antibiotics are commonly used for penetrating chest or abdominal injuries and severe head wounds. Short prophylactic courses are generally as effective as longer courses, supported by evidence in penetrating abdominal trauma showing no major outcome difference between 24-hour and 5-day regimens. Antibiotic levels can be altered by fluid shifts and hyperdynamic physiology, and data support higher doses for shorter durations, especially in trauma laparotomy patients. Short prophylaxis reduces infection in compound mandibular fractures. After traumatic splenectomy, the risk of early serious infection is low in isolated splenic injury but rises with greater injury and associated trauma; encapsulated organisms are key pathogens early and late. Administer pneumococcal and meningococcal vaccines once clinically stable after splenectomy. Strict infection control practices reduce hospital-acquired infections in severely injured patients.
Etiology
Trauma increases infection risk through vascular disruption and microcirculatory damage causing ischemia, edema, compartment syndromes, and necrosis; contamination of wounds and sterile spaces by soil or water exposure; post-shock immune dysfunction; reduced IgM responses after splenectomy compared with nonsplenectomized infected posttrauma patients; and additional immune suppression from corticosteroids used for head injury. Common infections in multiply injured patients include pneumonia and empyema, bacteremia or fungemia (including catheter-related), surgical site infection, intraabdominal infection, meningitis, urinary tract infection, sinus infection, wound infection, and Clostridioides difficile colitis after prior antibiotic exposure. Acinetobacter baumannii infections have been reported in injured military personnel from conflict regions, with some isolates susceptible only to carbapenems such as imipenem.
Diagnosis
History
Diagnosis is challenging because fever may be noninfectious after trauma, patients may be unable to provide history, examinations may be limited, and usual infection signs are less reliable in critically ill, multiply traumatized patients.
Physical Examination
Fever, tachycardia, and hypotension can occur after severe injury without infection. In critically ill patients, track ventilator requirements, sputum volume and character, and urine and stool output. In hospitalized trauma patients, perform a complete exam emphasizing indwelling devices, skin, operative wounds, abdomen, and respiratory findings. Inspect injured sites for local infection signs including pain, foul odor, erythema, swelling, purulent drainage, and delayed healing.
Diagnostic Tests and Interpretation
Laboratory Studies
Obtain CBC with differential, electrolytes, and kidney and liver function tests, recognizing leukocytosis may reflect trauma alone. Whenever possible, collect cultures from suspected sites before antibiotics, including blood, sputum, urine, cerebrospinal fluid studies and culture when penetrating head injury or CNS drains are present, wound cultures, and abscess cultures. With watery diarrhea and prior antibiotic exposure, test stool for C. difficile.
Imaging
Use chest radiography to assess pneumonia, especially in mechanically ventilated patients. Chest CT is more sensitive for thoracic infection in septic trauma patients and can guide correction of malpositioned or blocked thoracostomy tubes, though concurrent thoracic injuries can reduce test accuracy. Abdominal CT can identify intraabdominal infection such as perforation, colitis, cholecystitis, or abscess. For suspected extremity infection, ultrasound, CT, or MRI can help exclude abscess.
Diagnostic Procedures/Other
Image-guided or operative drainage of abscesses is diagnostic and therapeutic; send fluid for Gram stain, aerobic and anaerobic cultures, add fungal studies for abdominal or pelvic collections, and consider acid-fast bacilli smear and mycobacterial culture based on epidemiologic risk.
Differential Diagnosis
In severely injured patients, infection mimics include atelectasis, deep vein thrombosis, drug fever, allergic reactions or anaphylaxis, hypovolemia, large hematoma, sterile inflammation, pulmonary contusion, transfusion reactions, and central fever from brain injury.
Treatment
Medications
Correcting local anatomic problems such as open fractures or perforated abdominal organs is often more important than antibiotics alone. In trauma patients, unexplained hemodynamic instability not due to hypovolemia should prompt empiric antibiotics even if other infection signs are absent. Choose antibiotics based on suspected source, local resistance, trauma context (bites, water exposure, soil contamination), hospitalization duration and risk of resistant organisms, local MRSA prevalence, and allergies. If no source is identified, start broad-spectrum therapy including antistaphylococcal coverage plus broad gram-negative and anaerobic activity
.
Additional Treatment
Monitor clinical response and narrow therapy to culture and susceptibility results. If diagnostic evaluation is negative and the patient is stable, consider stopping antibiotics. Duration depends on infection site and clinical course. Remove central venous and urinary catheters as soon as they are no longer needed.
Issues for Referral
Severe injuries require urgent evaluation at experienced trauma centers with surgical and critical care capability. Infectious diseases consultation is useful when the patient is critically ill, not improving on therapy, or diagnosis remains uncertain.
Surgery/Other Procedures
Drain collections, debride necrotic tissue, and repair fractures or perforations promptly, and implement measures to mobilize respiratory secretions.
In-Patient Considerations
Initial Stabilization
Stabilize airway and circulation, provide rapid fluid resuscitation, and document all injuries.
Admission Criteria
Admit patients with penetrating injuries, fractures needing urgent repair, abnormal vital signs, impaired mental status, uncontrolled pain, or severe injuries. Burns meeting moderate to major thresholds require admission to specialized burn care centers.
Discharge Criteria
Discharge when fever has been absent for more than 24 hours, vital signs are stable, and follow-up for antibiotics and wound care is arranged.
Ongoing Care and Follow-Up
Patient Monitoring
Monitor closely for wound infection and healthcare-associated infections, which occur in a meaningful minority of hospitalized trauma patients.
Diet
Provide adequate nutritional support and consider nutrition consultation in severely injured hospitalized patients.
Patient Education
Teach warning signs of wound infection and provide clear instructions for wound care, including packing and dressing-change schedules.
Prognosis
Trauma-related infection increases mortality risk and is associated with worse functional outcomes during the year after injury compared with trauma patients without infection.
Complications
Serious outcomes include septic shock, respiratory failure, peritonitis and abdominal abscess, osteomyelitis, brain abscess, and acute acalculous cholecystitis.
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Infectious Disease and Microbiology – Adenovirus Infections
Adenovirus infections are caused by nonenveloped, double-stranded DNA viruses measuring approximately 70–80 nm in diameter. Human adenoviruses belong to the genus Mastadenovirus and include more than 50 serotypes. These viruses possess an icosahedral capsid composed of 20 triangular faces and 12 vertices. The genome consists of linear double-stranded DNA encoding structural and nonstructural proteins. Infection may result in either lytic replication or latent persistence, and certain serotypes have demonstrated oncogenic potential in animal models.
Adenoviruses contribute to a proportion of viral respiratory illnesses. Although rhinoviruses are the most common cause of acute respiratory infections, adenoviruses account for up to 5% of respiratory infections in children and fewer than 2% in adults. Infections occur most frequently from fall through spring. Transmission occurs via inhalation of aerosolized particles, direct inoculation of conjunctival mucosa, and possibly via the fecal–oral route. Outbreaks of acute respiratory disease due to specific serotypes are well documented among military recruits, particularly in winter and spring. Following infection, type-specific antibodies develop and provide protection against reinfection with the same serotype. Severe or disseminated disease may occur in immunocompromised individuals, including patients with AIDS, solid-organ or bone marrow transplant recipients, and children with congenital immunodeficiencies.
In children, adenovirus commonly causes acute upper respiratory tract infection characterized by prominent rhinitis. Lower respiratory involvement, including bronchiolitis and pneumonia, may occur. Pharyngoconjunctival fever is a distinctive syndrome seen in outbreaks, particularly in summer camps, presenting with low-grade fever for 3–5 days followed by rhinitis, sore throat, cervical lymphadenopathy, and conjunctivitis, typically resolving within 1–2 weeks. Adenovirus also causes pharyngitis and, in young children, acute diarrheal illness. Other manifestations include hemorrhagic cystitis and epidemic keratoconjunctivitis. In adults, acute respiratory disease presents with sore throat, gradual onset of fever that may reach 39°C, cough, coryza, and lymphadenopathy. In immunocompromised patients, adenovirus pneumonia may present abruptly with fever, rigors, malaise, nonproductive cough, gastrointestinal symptoms, headache, and arthralgia.
Physical examination may reveal pharyngeal edema, injection, and tonsillar enlargement with minimal exudate. Ocular involvement presents with conjunctival injection and discharge. In immunocompromised hosts, localizing findings may be minimal despite severe disease.
Definitive diagnosis is established by viral culture or detection of adenovirus from conjunctival, oropharyngeal, sputum, urine, or stool specimens. Viral cytopathic effects in tissue culture can be confirmed by immunofluorescence or other immunologic assays. Certain enteric adenovirus types require specialized cell lines or direct ELISA testing of stool. Serologic diagnosis may demonstrate rising antibody titers using complement fixation, neutralization assays, ELISA, or radioimmunoassay. In adenovirus pneumonia, chest radiography often shows bilateral diffuse interstitial infiltrates and occasionally pleural effusions. The clinical presentation is frequently indistinguishable from other viral respiratory infections or Mycoplasma pneumoniae.
Management is primarily supportive, as no specific antiviral therapy is routinely indicated for immunocompetent patients. Live oral vaccines targeting adenovirus types 4 and 7 are used in military settings to prevent outbreaks. In immunocompromised individuals with severe infection, treatment with cidofovir and intravenous immunoglobulin has shown benefit in some cases. Intravenous gamma globulin and type-specific antibodies may also be helpful. Ribavirin and ganciclovir have been used in selected cases, although evidence remains limited.
In transplant recipients and other immunocompromised patients, adenovirus pneumonia carries significant morbidity and mortality, which may exceed 60%, underscoring the importance of early recognition and supportive management.
Adenovirus infections are caused by nonenveloped, double-stranded DNA viruses measuring approximately 70–80 nm in diameter. Human adenoviruses belong to the genus Mastadenovirus and include more than 50 serotypes. These viruses possess an icosahedral capsid composed of 20 triangular faces and 12 vertices. The genome consists of linear double-stranded DNA encoding structural and nonstructural proteins. Infection may result in either lytic replication or latent persistence, and certain serotypes have demonstrated oncogenic potential in animal models.
Adenoviruses contribute to a proportion of viral respiratory illnesses. Although rhinoviruses are the most common cause of acute respiratory infections, adenoviruses account for up to 5% of respiratory infections in children and fewer than 2% in adults. Infections occur most frequently from fall through spring. Transmission occurs via inhalation of aerosolized particles, direct inoculation of conjunctival mucosa, and possibly via the fecal–oral route. Outbreaks of acute respiratory disease due to specific serotypes are well documented among military recruits, particularly in winter and spring. Following infection, type-specific antibodies develop and provide protection against reinfection with the same serotype. Severe or disseminated disease may occur in immunocompromised individuals, including patients with AIDS, solid-organ or bone marrow transplant recipients, and children with congenital immunodeficiencies.
In children, adenovirus commonly causes acute upper respiratory tract infection characterized by prominent rhinitis. Lower respiratory involvement, including bronchiolitis and pneumonia, may occur. Pharyngoconjunctival fever is a distinctive syndrome seen in outbreaks, particularly in summer camps, presenting with low-grade fever for 3–5 days followed by rhinitis, sore throat, cervical lymphadenopathy, and conjunctivitis, typically resolving within 1–2 weeks. Adenovirus also causes pharyngitis and, in young children, acute diarrheal illness. Other manifestations include hemorrhagic cystitis and epidemic keratoconjunctivitis. In adults, acute respiratory disease presents with sore throat, gradual onset of fever that may reach 39°C, cough, coryza, and lymphadenopathy. In immunocompromised patients, adenovirus pneumonia may present abruptly with fever, rigors, malaise, nonproductive cough, gastrointestinal symptoms, headache, and arthralgia.
Physical examination may reveal pharyngeal edema, injection, and tonsillar enlargement with minimal exudate. Ocular involvement presents with conjunctival injection and discharge. In immunocompromised hosts, localizing findings may be minimal despite severe disease.
Definitive diagnosis is established by viral culture or detection of adenovirus from conjunctival, oropharyngeal, sputum, urine, or stool specimens. Viral cytopathic effects in tissue culture can be confirmed by immunofluorescence or other immunologic assays. Certain enteric adenovirus types require specialized cell lines or direct ELISA testing of stool. Serologic diagnosis may demonstrate rising antibody titers using complement fixation, neutralization assays, ELISA, or radioimmunoassay. In adenovirus pneumonia, chest radiography often shows bilateral diffuse interstitial infiltrates and occasionally pleural effusions. The clinical presentation is frequently indistinguishable from other viral respiratory infections or Mycoplasma pneumoniae.
Management is primarily supportive, as no specific antiviral therapy is routinely indicated for immunocompetent patients. Live oral vaccines targeting adenovirus types 4 and 7 are used in military settings to prevent outbreaks. In immunocompromised individuals with severe infection, treatment with cidofovir and intravenous immunoglobulin has shown benefit in some cases. Intravenous gamma globulin and type-specific antibodies may also be helpful. Ribavirin and ganciclovir have been used in selected cases, although evidence remains limited.
In transplant recipients and other immunocompromised patients, adenovirus pneumonia carries significant morbidity and mortality, which may exceed 60%, underscoring the importance of early recognition and supportive management.
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Infectious Disease and Microbiology – Actinomycosis
Actinomycosis is a chronic, slowly progressive, suppurative, and tissue-destructive infection characterized by mass-like lesions and sinus tract formation. It most commonly affects the head and neck region but may also involve the thorax, abdomen, pelvis, central nervous system, bones, and soft tissues. The disease is indolent and often mimics malignancy or other chronic infections.
The reported incidence is approximately 1 per 300,000 population in the United States and about 1 per 100,000 in Europe. It occurs at all ages, with peak frequency in middle-aged adults, and has a male-to-female ratio of about 3:1. Risk factors include poor oral hygiene, dental manipulation, oral trauma, intrauterine contraceptive device (especially when used for more than 2 years), abdominal surgery, appendicitis, diverticulitis, foreign bodies, malnutrition, and immunodeficiency such as HIV infection, chronic granulomatous disease, or prolonged corticosteroid therapy. Cases have also been described in osteoradionecrosis and bisphosphonate-related mandibular osteonecrosis. Prevention includes maintaining good oral hygiene and, in women with long-term intrauterine devices and suspicious symptoms, device removal with short-term antibiotic therapy. Patient isolation is not required.
Humans are the natural reservoir. The organisms colonize the oral cavity, particularly dental plaque and tonsillar crypts, as commensals. Infection typically follows disruption of the mucosal barrier due to trauma or surgery, allowing invasion into deeper tissues. The disease spreads contiguously and occasionally hematogenously. Aspiration may lead to thoracic involvement, while abdominal and pelvic disease often follows bowel perforation, appendicitis, or diverticulitis. Although incubation is unclear, diagnosis is usually delayed because of the chronic course. Clinical forms include cervicofacial, thoracic, abdominal, pelvic, central nervous system, and disseminated disease.
Actinomyces species are microaerophilic or anaerobic, filamentous, branched, Gram-positive, non–acid-fast rods. Actinomyces israelii is the most frequently identified species, although A. naeslundii, A. meyeri, A. odontolyticus, and Propionibacterium propionica have also been implicated. These organisms are normal flora of the oral cavity and female genital tract. Most infections are polymicrobial, often involving anaerobic oral flora that may act as copathogens.
Clinical presentation varies by site. Patients may have low-grade fever, weight loss, and pain. Cervicofacial disease often presents with perimandibular swelling, trismus, and purplish discoloration of overlying skin, with sinus tract formation draining characteristic yellow “sulfur granules.” Thoracic disease presents with cough, chest pain, dyspnea, mass-like lesions, pleural thickening, empyema, chest wall invasion, and possible mediastinal or spinal involvement. Abdominal disease typically manifests as a firm mass, often in the right iliac fossa following appendicitis, or in the left lower quadrant after diverticulitis, sometimes with chronic perianal abscesses and fistulae. Pelvic disease may present as abscesses or a “frozen pelvis.” Central nervous system involvement causes focal neurologic deficits or chronic meningitis.
Diagnosis requires high suspicion, especially when mass lesions coexist with draining sinuses and sulfur granules. Specimens should be obtained before antibiotic therapy. Gram stain of pus or tissue from sterile sites demonstrating filamentous, Gram-positive, non–acid-fast organisms is more sensitive than culture. Swab cultures are not recommended, and specimens must be processed anaerobically. Direct immunofluorescence may assist in specific cases. Imaging with CT or MRI helps determine disease extent. Lung disease may show the “open bronchus sign.” Bone involvement may demonstrate a saw-toothed appearance, and CNS disease often appears as single or multiloculated lesions with surrounding edema. Differential diagnosis includes malignancy, nocardiosis, tuberculosis, botryomycosis, and endemic fungal infections.
Treatment consists of prolonged high-dose penicillin therapy. Recommended first-line therapy includes intravenous penicillin G (10–24 million units daily in divided doses) for 2–6 weeks, followed by oral penicillin V for 6–12 months, or intravenous ampicillin followed by oral amoxicillin for similar duration. Mild cervicofacial disease may be treated with oral therapy alone. Alternatives for penicillin-allergic patients include tetracyclines, erythromycin, or clindamycin. Surgical intervention, including abscess drainage or excision of fibrotic tissue, is often necessary.
Prognosis is generally excellent with appropriate prolonged therapy, as resistance among Actinomyces species is rare. Treatment failure usually suggests an undrained abscess or presence of resistant copathogens. Potential complications include disseminated disease and bowel obstruction in extensive abdominal or pelvic involvement.
Actinomycosis is a chronic, slowly progressive, suppurative, and tissue-destructive infection characterized by mass-like lesions and sinus tract formation. It most commonly affects the head and neck region but may also involve the thorax, abdomen, pelvis, central nervous system, bones, and soft tissues. The disease is indolent and often mimics malignancy or other chronic infections.
The reported incidence is approximately 1 per 300,000 population in the United States and about 1 per 100,000 in Europe. It occurs at all ages, with peak frequency in middle-aged adults, and has a male-to-female ratio of about 3:1. Risk factors include poor oral hygiene, dental manipulation, oral trauma, intrauterine contraceptive device (especially when used for more than 2 years), abdominal surgery, appendicitis, diverticulitis, foreign bodies, malnutrition, and immunodeficiency such as HIV infection, chronic granulomatous disease, or prolonged corticosteroid therapy. Cases have also been described in osteoradionecrosis and bisphosphonate-related mandibular osteonecrosis. Prevention includes maintaining good oral hygiene and, in women with long-term intrauterine devices and suspicious symptoms, device removal with short-term antibiotic therapy. Patient isolation is not required.
Humans are the natural reservoir. The organisms colonize the oral cavity, particularly dental plaque and tonsillar crypts, as commensals. Infection typically follows disruption of the mucosal barrier due to trauma or surgery, allowing invasion into deeper tissues. The disease spreads contiguously and occasionally hematogenously. Aspiration may lead to thoracic involvement, while abdominal and pelvic disease often follows bowel perforation, appendicitis, or diverticulitis. Although incubation is unclear, diagnosis is usually delayed because of the chronic course. Clinical forms include cervicofacial, thoracic, abdominal, pelvic, central nervous system, and disseminated disease.
Actinomyces species are microaerophilic or anaerobic, filamentous, branched, Gram-positive, non–acid-fast rods. Actinomyces israelii is the most frequently identified species, although A. naeslundii, A. meyeri, A. odontolyticus, and Propionibacterium propionica have also been implicated. These organisms are normal flora of the oral cavity and female genital tract. Most infections are polymicrobial, often involving anaerobic oral flora that may act as copathogens.
Clinical presentation varies by site. Patients may have low-grade fever, weight loss, and pain. Cervicofacial disease often presents with perimandibular swelling, trismus, and purplish discoloration of overlying skin, with sinus tract formation draining characteristic yellow “sulfur granules.” Thoracic disease presents with cough, chest pain, dyspnea, mass-like lesions, pleural thickening, empyema, chest wall invasion, and possible mediastinal or spinal involvement. Abdominal disease typically manifests as a firm mass, often in the right iliac fossa following appendicitis, or in the left lower quadrant after diverticulitis, sometimes with chronic perianal abscesses and fistulae. Pelvic disease may present as abscesses or a “frozen pelvis.” Central nervous system involvement causes focal neurologic deficits or chronic meningitis.
Diagnosis requires high suspicion, especially when mass lesions coexist with draining sinuses and sulfur granules. Specimens should be obtained before antibiotic therapy. Gram stain of pus or tissue from sterile sites demonstrating filamentous, Gram-positive, non–acid-fast organisms is more sensitive than culture. Swab cultures are not recommended, and specimens must be processed anaerobically. Direct immunofluorescence may assist in specific cases. Imaging with CT or MRI helps determine disease extent. Lung disease may show the “open bronchus sign.” Bone involvement may demonstrate a saw-toothed appearance, and CNS disease often appears as single or multiloculated lesions with surrounding edema. Differential diagnosis includes malignancy, nocardiosis, tuberculosis, botryomycosis, and endemic fungal infections.
Treatment consists of prolonged high-dose penicillin therapy. Recommended first-line therapy includes intravenous penicillin G (10–24 million units daily in divided doses) for 2–6 weeks, followed by oral penicillin V for 6–12 months, or intravenous ampicillin followed by oral amoxicillin for similar duration. Mild cervicofacial disease may be treated with oral therapy alone. Alternatives for penicillin-allergic patients include tetracyclines, erythromycin, or clindamycin. Surgical intervention, including abscess drainage or excision of fibrotic tissue, is often necessary.
Prognosis is generally excellent with appropriate prolonged therapy, as resistance among Actinomyces species is rare. Treatment failure usually suggests an undrained abscess or presence of resistant copathogens. Potential complications include disseminated disease and bowel obstruction in extensive abdominal or pelvic involvement.
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Infectious Disease and Microbiology – Acne Vulgaris
Acne vulgaris (common acne) is a chronic inflammatory disorder of the pilosebaceous unit, particularly the sebaceous follicles. It is characterized by comedones, papules, pustules, nodules, and in more severe cases, scarring. The condition primarily affects areas rich in sebaceous glands, including the face, neck, chest, upper back, and upper arms.
Acne is one of the most common skin diseases, affecting more than 85% of individuals at some point between adolescence and early adulthood, with a mean age of approximately 24 years. It accounts for up to 2 million office visits annually among adolescents aged 15–19 years. A major risk factor is increased responsiveness of sebaceous glands and keratinocytes to androgenic hormones, particularly during puberty. Elevated androgen levels such as testosterone, dehydroepiandrosterone sulfate (DHEAS), or androstenedione may worsen acne severity, especially in women.
The pathophysiology involves inflammatory changes within sebaceous follicles, leading to accumulation of lipid-rich sebum and proliferation of Cutibacterium acnes (formerly Propionibacterium acnes), a Gram-positive anaerobic bacterium that normally exists in low numbers on the skin. Overgrowth of this organism within the follicle triggers inflammation, follicular rupture, and extension of inflammation into the surrounding dermis. This process results in the formation of papules, pustules, and nodules.
Clinically, patients present with open comedones (blackheads) or closed comedones (whiteheads). As inflammation progresses, lesions may become painful and form pustules or nodules. Scarring suggests more aggressive disease. Acne is classified as mild when primarily noninflammatory comedones are present, moderate when inflammatory papules and pustules affect larger skin areas, and severe when large painful nodules with potential scarring are present.
Treatment depends on severity. Mild to moderate acne often responds to topical therapy, including retinoids, benzoyl peroxide, and topical antimicrobials. Retinoids reduce sebaceous gland activity and normalize follicular keratinization. Benzoyl peroxide acts as a bactericidal agent and is often combined with topical antibiotics to reduce resistance. More severe cases may require oral antibiotics such as doxycycline, minocycline, tetracycline, trimethoprim-sulfamethoxazole, erythromycin, or clindamycin, although resistance has become increasingly common.
For severe nodulocystic acne or cases associated with scarring, oral isotretinoin is indicated. It reduces sebaceous gland size and sebum production, inhibits bacterial growth, and has anti-inflammatory properties. However, isotretinoin is highly teratogenic and may cause hypertriglyceridemia. Women of childbearing age must use two forms of contraception during treatment. Reports have also suggested possible associations with mood changes.
Additional therapies may include spironolactone or oral contraceptives in patients with hyperandrogenism. Intralesional corticosteroids can be used for severe inflammatory nodules. With appropriate treatment and adherence, most patients experience significant improvement, and early management helps reduce the risk of permanent scarring.
Acne vulgaris (common acne) is a chronic inflammatory disorder of the pilosebaceous unit, particularly the sebaceous follicles. It is characterized by comedones, papules, pustules, nodules, and in more severe cases, scarring. The condition primarily affects areas rich in sebaceous glands, including the face, neck, chest, upper back, and upper arms.
Acne is one of the most common skin diseases, affecting more than 85% of individuals at some point between adolescence and early adulthood, with a mean age of approximately 24 years. It accounts for up to 2 million office visits annually among adolescents aged 15–19 years. A major risk factor is increased responsiveness of sebaceous glands and keratinocytes to androgenic hormones, particularly during puberty. Elevated androgen levels such as testosterone, dehydroepiandrosterone sulfate (DHEAS), or androstenedione may worsen acne severity, especially in women.
The pathophysiology involves inflammatory changes within sebaceous follicles, leading to accumulation of lipid-rich sebum and proliferation of Cutibacterium acnes (formerly Propionibacterium acnes), a Gram-positive anaerobic bacterium that normally exists in low numbers on the skin. Overgrowth of this organism within the follicle triggers inflammation, follicular rupture, and extension of inflammation into the surrounding dermis. This process results in the formation of papules, pustules, and nodules.
Clinically, patients present with open comedones (blackheads) or closed comedones (whiteheads). As inflammation progresses, lesions may become painful and form pustules or nodules. Scarring suggests more aggressive disease. Acne is classified as mild when primarily noninflammatory comedones are present, moderate when inflammatory papules and pustules affect larger skin areas, and severe when large painful nodules with potential scarring are present.
Treatment depends on severity. Mild to moderate acne often responds to topical therapy, including retinoids, benzoyl peroxide, and topical antimicrobials. Retinoids reduce sebaceous gland activity and normalize follicular keratinization. Benzoyl peroxide acts as a bactericidal agent and is often combined with topical antibiotics to reduce resistance. More severe cases may require oral antibiotics such as doxycycline, minocycline, tetracycline, trimethoprim-sulfamethoxazole, erythromycin, or clindamycin, although resistance has become increasingly common.
For severe nodulocystic acne or cases associated with scarring, oral isotretinoin is indicated. It reduces sebaceous gland size and sebum production, inhibits bacterial growth, and has anti-inflammatory properties. However, isotretinoin is highly teratogenic and may cause hypertriglyceridemia. Women of childbearing age must use two forms of contraception during treatment. Reports have also suggested possible associations with mood changes.
Additional therapies may include spironolactone or oral contraceptives in patients with hyperandrogenism. Intralesional corticosteroids can be used for severe inflammatory nodules. With appropriate treatment and adherence, most patients experience significant improvement, and early management helps reduce the risk of permanent scarring.
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Infectious Diseases and Microbiology: Vaginal Discharge / Vaginitis
Vaginal discharge may be physiologic or pathologic. Normal vaginal discharge, also referred to as leukorrhea, consists of cervical mucus and desquamated epithelial cells and is not associated with irritation, odor, or discomfort. In contrast, pathologic discharge is usually associated with infection and may present with abnormal color due to increased polymorphonuclear leukocytes, increased volume, malodor, vulvar pruritus, burning, dysuria, or dyspareunia. The three most common infectious causes of vaginitis are bacterial vaginosis, trichomoniasis, and candidiasis. Bacterial vaginosis represents a disruption of normal vaginal flora in which hydrogen-peroxide–producing lactobacilli are replaced by anaerobic organisms, mycoplasmas, and Gardnerella vaginalis.
Evaluation begins with a detailed history focusing on the characteristics of the discharge, associated symptoms, prior similar episodes, and a complete sexual history. Office-based diagnostic evaluation includes measurement of vaginal pH, performance of the amine (“whiff”) test by adding 10% potassium hydroxide to vaginal secretions, and microscopic examination of saline wet mount preparations to identify clue cells, motile trichomonads, and white blood cells. A potassium hydroxide preparation may reveal Candida pseudohyphae. In sexually active women, both endocervical and high vaginal swabs should be obtained. Chlamydial testing requires sampling of the squamocolumnar junction for culture or nucleic acid amplification testing. Screening cultures may include selective media for Neisseria gonorrhoeae, Candida species, and beta-hemolytic streptococci.
Bacterial vaginosis is the most common cause of vulvovaginal symptoms, followed by vulvovaginal candidiasis. Trichomoniasis is less common in developed countries. Risk factors for vaginal infections include unprotected sexual contact, multiple sexual partners, young age, and certain socioeconomic factors. Bacterial vaginosis is particularly associated with new or multiple sexual partners.
Clinically, vulvovaginal candidiasis often presents with vulvar pruritus and burning, dysuria at the urethral orifice, vaginal erythema, and occasionally thick, white, curd-like discharge. However, only a minority of patients exhibit the classic discharge. Trichomoniasis commonly presents with malodorous yellow discharge, vulvar erythema, itching, dysuria, urinary frequency, and dyspareunia, although symptoms are nonspecific. Bacterial vaginosis typically produces a thin, homogeneous discharge with a characteristic fishy odor that may be more noticeable after intercourse. In the absence of identifiable pathogens, vulvar inflammation may reflect noninfectious irritation or allergic reactions.
Diagnosis of trichomoniasis is commonly made by identifying motile organisms on saline wet mount, although sensitivity is moderate. Direct immunofluorescent testing and culture are more sensitive when available. Candidiasis is diagnosed by microscopic identification of budding yeast or pseudohyphae on saline or potassium hydroxide preparation. Vaginal pH in candidiasis is typically normal (≤4.5), and the amine test is negative. The presence of white blood cells without yeast or trichomonads suggests cervicitis. Absence of organisms on microscopy does not exclude infection, as culture or PCR may be required.
Treatment depends on the identified etiology. Trichomoniasis is treated with a single 2 g oral dose of metronidazole. Bacterial vaginosis is treated with oral metronidazole 500 mg twice daily for seven days or clindamycin 300 mg twice daily for seven days. Intravaginal metronidazole gel or clindamycin cream are effective alternatives. Symptomatic candidiasis is treated primarily with intravaginal azole antifungals such as clotrimazole, miconazole, butoconazole, or terconazole. Oral fluconazole as a single dose is an alternative but is more costly. In pregnancy, intravaginal azoles may be used after the first trimester.
Recurrent vulvovaginal candidiasis, defined as four or more episodes per year, may occur more frequently in women with diabetes mellitus or HIV infection. Vaginal trichomoniasis and bacterial vaginosis during pregnancy are associated with increased risk of preterm labor. Bacterial vaginosis is also associated with pelvic infections, postoperative endometritis, neonatal sepsis, increased risk of HIV acquisition and transmission, and increased susceptibility to other sexually transmitted infections.
Vaginal discharge may be physiologic or pathologic. Normal vaginal discharge, also referred to as leukorrhea, consists of cervical mucus and desquamated epithelial cells and is not associated with irritation, odor, or discomfort. In contrast, pathologic discharge is usually associated with infection and may present with abnormal color due to increased polymorphonuclear leukocytes, increased volume, malodor, vulvar pruritus, burning, dysuria, or dyspareunia. The three most common infectious causes of vaginitis are bacterial vaginosis, trichomoniasis, and candidiasis. Bacterial vaginosis represents a disruption of normal vaginal flora in which hydrogen-peroxide–producing lactobacilli are replaced by anaerobic organisms, mycoplasmas, and Gardnerella vaginalis.
Evaluation begins with a detailed history focusing on the characteristics of the discharge, associated symptoms, prior similar episodes, and a complete sexual history. Office-based diagnostic evaluation includes measurement of vaginal pH, performance of the amine (“whiff”) test by adding 10% potassium hydroxide to vaginal secretions, and microscopic examination of saline wet mount preparations to identify clue cells, motile trichomonads, and white blood cells. A potassium hydroxide preparation may reveal Candida pseudohyphae. In sexually active women, both endocervical and high vaginal swabs should be obtained. Chlamydial testing requires sampling of the squamocolumnar junction for culture or nucleic acid amplification testing. Screening cultures may include selective media for Neisseria gonorrhoeae, Candida species, and beta-hemolytic streptococci.
Bacterial vaginosis is the most common cause of vulvovaginal symptoms, followed by vulvovaginal candidiasis. Trichomoniasis is less common in developed countries. Risk factors for vaginal infections include unprotected sexual contact, multiple sexual partners, young age, and certain socioeconomic factors. Bacterial vaginosis is particularly associated with new or multiple sexual partners.
Clinically, vulvovaginal candidiasis often presents with vulvar pruritus and burning, dysuria at the urethral orifice, vaginal erythema, and occasionally thick, white, curd-like discharge. However, only a minority of patients exhibit the classic discharge. Trichomoniasis commonly presents with malodorous yellow discharge, vulvar erythema, itching, dysuria, urinary frequency, and dyspareunia, although symptoms are nonspecific. Bacterial vaginosis typically produces a thin, homogeneous discharge with a characteristic fishy odor that may be more noticeable after intercourse. In the absence of identifiable pathogens, vulvar inflammation may reflect noninfectious irritation or allergic reactions.
Diagnosis of trichomoniasis is commonly made by identifying motile organisms on saline wet mount, although sensitivity is moderate. Direct immunofluorescent testing and culture are more sensitive when available. Candidiasis is diagnosed by microscopic identification of budding yeast or pseudohyphae on saline or potassium hydroxide preparation. Vaginal pH in candidiasis is typically normal (≤4.5), and the amine test is negative. The presence of white blood cells without yeast or trichomonads suggests cervicitis. Absence of organisms on microscopy does not exclude infection, as culture or PCR may be required.
Treatment depends on the identified etiology. Trichomoniasis is treated with a single 2 g oral dose of metronidazole. Bacterial vaginosis is treated with oral metronidazole 500 mg twice daily for seven days or clindamycin 300 mg twice daily for seven days. Intravaginal metronidazole gel or clindamycin cream are effective alternatives. Symptomatic candidiasis is treated primarily with intravaginal azole antifungals such as clotrimazole, miconazole, butoconazole, or terconazole. Oral fluconazole as a single dose is an alternative but is more costly. In pregnancy, intravaginal azoles may be used after the first trimester.
Recurrent vulvovaginal candidiasis, defined as four or more episodes per year, may occur more frequently in women with diabetes mellitus or HIV infection. Vaginal trichomoniasis and bacterial vaginosis during pregnancy are associated with increased risk of preterm labor. Bacterial vaginosis is also associated with pelvic infections, postoperative endometritis, neonatal sepsis, increased risk of HIV acquisition and transmission, and increased susceptibility to other sexually transmitted infections.
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Infectious Diseases and Microbiology: Urethritis and Urethral Discharge
Basics
Description
Urethritis is inflammation of the urethra, often presenting with purulent or mucopurulent urethral discharge. In women, urethral syndrome or dysuria with sterile pyuria describes dysuria and urinary frequency with few or no bacteria detected in urine.
Approach to the Patient
Symptoms range from mild intermittent discomfort to persistent pain. History should include onset and duration of dysuria, associated symptoms, characteristics of discharge, and prior sexually transmitted infections. A complete genital examination is required. In men, palpate testes and spermatic cord to exclude epididymitis and evaluate for prostatitis; assess for cystitis in both sexes. To obtain discharge for examination, the urethra should be gently milked after the patient has avoided urination for several hours, ideally overnight.
Epidemiology
Urethritis is more common in men and represents one of the most frequently recognized sexually transmitted infections. Nongonococcal urethritis remains prevalent. Gonorrhea continues to affect adolescents and young adults disproportionately, particularly women aged 15–24 years. A substantial proportion of nongonococcal urethritis is caused by Chlamydia trachomatis. Antimicrobial resistance patterns, including quinolone-resistant Neisseria gonorrhoeae, have influenced treatment recommendations. Endourethral syphilitic chancre should also be considered in appropriate settings.
Risk Factors
Transmission risk depends on sexual exposure type. A high proportion of women exposed to men with urethral gonorrhea develop cervicitis, whereas fewer exposed men acquire infection from infected women. Incidence is highest among young, single individuals of lower socioeconomic and educational status.
General Prevention
Condom use reduces transmission of most sexually transmitted infections. Sexual partners of individuals with gonococcal or nongonococcal urethritis require evaluation and treatment to prevent reinfection and complications. Women with urinary symptoms without bacteriuria should be tested for N. gonorrhoeae. Patients diagnosed with urethritis should undergo screening for other sexually transmitted infections.
Etiology
Infectious causes include N. gonorrhoeae, C. trachomatis, Ureaplasma urealyticum, Mycoplasma genitalium, Trichomonas vaginalis, herpes simplex virus, and adenovirus. Noninfectious causes include Stevens–Johnson syndrome, granulomatosis with polyangiitis, chemical or mechanical irritation, and reactive arthritis (Reiter syndrome).
Diagnosis
Most men with urethral gonorrhea develop symptoms within days to two weeks after exposure, whereas nongonococcal urethritis typically has a 7–14 day incubation period. Dysuria is common in both conditions. Gonococcal discharge is usually purulent; nongonococcal discharge is less often purulent. Acute urethral syndrome presents with dysuria, urgency, and frequency.
Diagnostic Tests and Interpretation
Laboratory Studies
Gram-stained urethral smear showing five or more neutrophils per high-power field supports urethritis. Intracellular gram-negative diplococci confirm gonorrhea. Absence of diplococci suggests nongonococcal urethritis. Gram stain has high sensitivity for gonococcal infection in symptomatic men. First-void urine sediment may also demonstrate inflammatory cells. Nucleic acid amplification testing for N. gonorrhoeae and C. trachomatis is highly sensitive and specific and is recommended to guide patient and partner management. Candida has occasionally been implicated in urethritis when no other pathogen is identified.
Differential Diagnosis
Exclude systemic complications such as disseminated gonococcal infection or reactive arthritis. Consider bacterial prostatitis, cystitis, and in women, pyelonephritis if fever or flank pain is present. In sterile pyuria, evaluate for sexually transmitted pathogens such as C. trachomatis and N. gonorrhoeae, as well as other causes including tuberculosis or prostatitis.
Treatment
Medications
Gonococcal urethritis requires ceftriaxone in a single intramuscular dose, and most patients should also receive therapy targeting chlamydia. Nongonococcal urethritis is treated with doxycycline for seven days or a single dose of azithromycin. Alternative regimens include oral cephalosporins or spectinomycin where available. Fluoroquinolones are no longer recommended for gonorrhea due to resistance. Persistent or recurrent symptoms warrant reassessment for reinfection, treatment nonadherence, resistant strains, or coinfection such as T. vaginalis, which may require metronidazole. Recurrent nongonococcal urethritis may need prolonged therapy and evaluation for prostatic or structural abnormalities.
Ongoing Care and Follow-Up
Persistent hematuria after treatment requires urologic evaluation. Recurrence may reflect reinfection, coinfection, or treatment failure.
Complications
Chlamydia can cause salpingitis or bartholinitis and may result in neonatal conjunctivitis or pneumonia. Ureaplasma carriage has been associated with infertility. Both N. gonorrhoeae and C. trachomatis can cause acute epididymitis.
Basics
Description
Urethritis is inflammation of the urethra, often presenting with purulent or mucopurulent urethral discharge. In women, urethral syndrome or dysuria with sterile pyuria describes dysuria and urinary frequency with few or no bacteria detected in urine.
Approach to the Patient
Symptoms range from mild intermittent discomfort to persistent pain. History should include onset and duration of dysuria, associated symptoms, characteristics of discharge, and prior sexually transmitted infections. A complete genital examination is required. In men, palpate testes and spermatic cord to exclude epididymitis and evaluate for prostatitis; assess for cystitis in both sexes. To obtain discharge for examination, the urethra should be gently milked after the patient has avoided urination for several hours, ideally overnight.
Epidemiology
Urethritis is more common in men and represents one of the most frequently recognized sexually transmitted infections. Nongonococcal urethritis remains prevalent. Gonorrhea continues to affect adolescents and young adults disproportionately, particularly women aged 15–24 years. A substantial proportion of nongonococcal urethritis is caused by Chlamydia trachomatis. Antimicrobial resistance patterns, including quinolone-resistant Neisseria gonorrhoeae, have influenced treatment recommendations. Endourethral syphilitic chancre should also be considered in appropriate settings.
Risk Factors
Transmission risk depends on sexual exposure type. A high proportion of women exposed to men with urethral gonorrhea develop cervicitis, whereas fewer exposed men acquire infection from infected women. Incidence is highest among young, single individuals of lower socioeconomic and educational status.
General Prevention
Condom use reduces transmission of most sexually transmitted infections. Sexual partners of individuals with gonococcal or nongonococcal urethritis require evaluation and treatment to prevent reinfection and complications. Women with urinary symptoms without bacteriuria should be tested for N. gonorrhoeae. Patients diagnosed with urethritis should undergo screening for other sexually transmitted infections.
Etiology
Infectious causes include N. gonorrhoeae, C. trachomatis, Ureaplasma urealyticum, Mycoplasma genitalium, Trichomonas vaginalis, herpes simplex virus, and adenovirus. Noninfectious causes include Stevens–Johnson syndrome, granulomatosis with polyangiitis, chemical or mechanical irritation, and reactive arthritis (Reiter syndrome).
Diagnosis
Most men with urethral gonorrhea develop symptoms within days to two weeks after exposure, whereas nongonococcal urethritis typically has a 7–14 day incubation period. Dysuria is common in both conditions. Gonococcal discharge is usually purulent; nongonococcal discharge is less often purulent. Acute urethral syndrome presents with dysuria, urgency, and frequency.
Diagnostic Tests and Interpretation
Laboratory Studies
Gram-stained urethral smear showing five or more neutrophils per high-power field supports urethritis. Intracellular gram-negative diplococci confirm gonorrhea. Absence of diplococci suggests nongonococcal urethritis. Gram stain has high sensitivity for gonococcal infection in symptomatic men. First-void urine sediment may also demonstrate inflammatory cells. Nucleic acid amplification testing for N. gonorrhoeae and C. trachomatis is highly sensitive and specific and is recommended to guide patient and partner management. Candida has occasionally been implicated in urethritis when no other pathogen is identified.
Differential Diagnosis
Exclude systemic complications such as disseminated gonococcal infection or reactive arthritis. Consider bacterial prostatitis, cystitis, and in women, pyelonephritis if fever or flank pain is present. In sterile pyuria, evaluate for sexually transmitted pathogens such as C. trachomatis and N. gonorrhoeae, as well as other causes including tuberculosis or prostatitis.
Treatment
Medications
Gonococcal urethritis requires ceftriaxone in a single intramuscular dose, and most patients should also receive therapy targeting chlamydia. Nongonococcal urethritis is treated with doxycycline for seven days or a single dose of azithromycin. Alternative regimens include oral cephalosporins or spectinomycin where available. Fluoroquinolones are no longer recommended for gonorrhea due to resistance. Persistent or recurrent symptoms warrant reassessment for reinfection, treatment nonadherence, resistant strains, or coinfection such as T. vaginalis, which may require metronidazole. Recurrent nongonococcal urethritis may need prolonged therapy and evaluation for prostatic or structural abnormalities.
Ongoing Care and Follow-Up
Persistent hematuria after treatment requires urologic evaluation. Recurrence may reflect reinfection, coinfection, or treatment failure.
Complications
Chlamydia can cause salpingitis or bartholinitis and may result in neonatal conjunctivitis or pneumonia. Ureaplasma carriage has been associated with infertility. Both N. gonorrhoeae and C. trachomatis can cause acute epididymitis.
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Infectious Disease and Microbiology – Bacillary Angiomatosis / Peliosis Hepatica
Bacillary angiomatosis (BA) and peliosis hepatica (PH) are rare vascular proliferative infections caused by Bartonella species, most commonly affecting immunocompromised individuals, particularly those with advanced HIV infection and T-cell deficiency. Bacillary angiomatosis typically refers to the cutaneous or disseminated vascular form, whereas peliosis hepatica describes the visceral form involving blood-filled cystic lesions in the liver. If left untreated, the disease can be fatal.
This condition is globally distributed but uncommon. It is most frequently reported in individuals with HIV infection, particularly those with CD4 counts below 100 cells/mm³. Other risk factors include immunosuppression from transplantation or malignancy, poor sanitary conditions, homelessness, and close contact with cats. Bartonella henselae is most often associated with bacillary angiomatosis and cat exposure, while Bartonella quintana is linked to body louse infestation and is more commonly associated with bacteremia in homeless populations.
Preventive measures for immunocompromised individuals include careful handling of cats. Patients are advised to obtain healthy cats older than one year, practice strict hand hygiene after cleaning litter boxes, and avoid scratches or bites. Routine declawing or testing of cats is not recommended. Primary prophylaxis is generally not advised, although macrolides may offer protective effects against Bartonella infection. The need for lifelong suppressive therapy in HIV-infected patients has not been clearly established.
After an incubation period of at least one week, clinical manifestations can range from isolated bacteremia to extensive cutaneous, visceral, osseous, or central nervous system involvement. Constitutional symptoms such as fever, malaise, weight loss, and anemia are common. Peliosis hepatica often presents with persistent fever, abdominal pain, nausea, vomiting, and progressive hepatomegaly.
Cutaneous manifestations occur in the majority of patients with bacillary angiomatosis. Lesions are typically bright red, elevated papules that may vary from a few millimeters to several centimeters in size and may number from one to hundreds. Smaller lesions may have a thin overlying epidermis, while larger lesions may ulcerate or bleed easily and are often surrounded by a collarette. Subcutaneous nodules may develop without visible skin changes. Cellulitic plaque-like lesions may overlie deeper bone involvement. Extracutaneous manifestations include bone lesions, visceral involvement of the liver and spleen, lymphadenopathy, and, rarely, brain abscesses. Bone disease may present with pain alone or in association with overlying skin lesions. Peliosis hepatica is characterized by massive hepatomegaly and sometimes splenomegaly.
Diagnosis relies on tissue biopsy. Histologic examination using hematoxylin and eosin staining may show granular purple material representing organisms, while Warthin–Starry or Brown–Hopps staining can better visualize the bacteria. The organisms appear singly or in clusters. Culture is difficult and requires prolonged incubation (at least 21 days) using lysis-centrifugation techniques. Polymerase chain reaction (PCR) testing can aid in species identification. Serologic testing has limited sensitivity in immunocompromised patients. Laboratory findings may include mild elevation of transaminases, marked elevation of alkaline phosphatase, and mild-to-moderate pancytopenia in visceral disease.
Imaging findings depend on organ involvement. Bone radiographs may reveal well-circumscribed lytic lesions or cortical destruction with aggressive periosteal reaction. CT scans may demonstrate hepatosplenomegaly and abdominal lymphadenopathy, with heterogeneous liver parenchyma. Liver biopsy in peliosis hepatica shows dilated, blood-filled cystic spaces within the hepatic parenchyma, often with associated necrosis in advanced cases.
The differential diagnosis includes Kaposi’s sarcoma, pyogenic granulomas, angiomas, and other vascular tumors. Kaposi’s sarcoma may coexist with bacillary angiomatosis and should be considered, particularly if lesions fail to improve with antibiotic therapy.
Treatment begins with evaluation of the extent of organ involvement. First-line therapy consists of erythromycin 500 mg orally every six hours or doxycycline 100 mg orally twice daily. Treatment duration is generally three months for bacillary angiomatosis and four months for peliosis hepatica, with longer courses required in immunocompromised patients. A Jarisch–Herxheimer reaction may occur after initiation of therapy; pretreatment with antipyretics for the first 72 hours may help.
For patients intolerant to first-line therapy, azithromycin or clarithromycin may be used. In severe, life-threatening, or central nervous system disease—particularly in immunocompromised individuals—combination therapy with rifampin added to erythromycin or doxycycline is recommended. TMP-SMX and ciprofloxacin have shown inconsistent results. Most patients can be managed as outpatients, though hospitalization and intravenous therapy are necessary for extensive or fulminant disease.
Clinical improvement is often observed within 4–7 days of therapy, with near-complete resolution of lesions by 3–4 weeks. Relapses occur in approximately 15% of cases and may require prolonged suppressive therapy. Monitoring includes clinical assessment, serial liver function tests in visceral disease, and imaging studies for bone involvement.
Complications of visceral disease include anemia, pancytopenia due to hypersplenism, and splenic rupture with hemoperitoneum. Early recognition and prolonged antimicrobial therapy are essential for favorable outcomes.
Bacillary angiomatosis (BA) and peliosis hepatica (PH) are rare vascular proliferative infections caused by Bartonella species, most commonly affecting immunocompromised individuals, particularly those with advanced HIV infection and T-cell deficiency. Bacillary angiomatosis typically refers to the cutaneous or disseminated vascular form, whereas peliosis hepatica describes the visceral form involving blood-filled cystic lesions in the liver. If left untreated, the disease can be fatal.
This condition is globally distributed but uncommon. It is most frequently reported in individuals with HIV infection, particularly those with CD4 counts below 100 cells/mm³. Other risk factors include immunosuppression from transplantation or malignancy, poor sanitary conditions, homelessness, and close contact with cats. Bartonella henselae is most often associated with bacillary angiomatosis and cat exposure, while Bartonella quintana is linked to body louse infestation and is more commonly associated with bacteremia in homeless populations.
Preventive measures for immunocompromised individuals include careful handling of cats. Patients are advised to obtain healthy cats older than one year, practice strict hand hygiene after cleaning litter boxes, and avoid scratches or bites. Routine declawing or testing of cats is not recommended. Primary prophylaxis is generally not advised, although macrolides may offer protective effects against Bartonella infection. The need for lifelong suppressive therapy in HIV-infected patients has not been clearly established.
After an incubation period of at least one week, clinical manifestations can range from isolated bacteremia to extensive cutaneous, visceral, osseous, or central nervous system involvement. Constitutional symptoms such as fever, malaise, weight loss, and anemia are common. Peliosis hepatica often presents with persistent fever, abdominal pain, nausea, vomiting, and progressive hepatomegaly.
Cutaneous manifestations occur in the majority of patients with bacillary angiomatosis. Lesions are typically bright red, elevated papules that may vary from a few millimeters to several centimeters in size and may number from one to hundreds. Smaller lesions may have a thin overlying epidermis, while larger lesions may ulcerate or bleed easily and are often surrounded by a collarette. Subcutaneous nodules may develop without visible skin changes. Cellulitic plaque-like lesions may overlie deeper bone involvement. Extracutaneous manifestations include bone lesions, visceral involvement of the liver and spleen, lymphadenopathy, and, rarely, brain abscesses. Bone disease may present with pain alone or in association with overlying skin lesions. Peliosis hepatica is characterized by massive hepatomegaly and sometimes splenomegaly.
Diagnosis relies on tissue biopsy. Histologic examination using hematoxylin and eosin staining may show granular purple material representing organisms, while Warthin–Starry or Brown–Hopps staining can better visualize the bacteria. The organisms appear singly or in clusters. Culture is difficult and requires prolonged incubation (at least 21 days) using lysis-centrifugation techniques. Polymerase chain reaction (PCR) testing can aid in species identification. Serologic testing has limited sensitivity in immunocompromised patients. Laboratory findings may include mild elevation of transaminases, marked elevation of alkaline phosphatase, and mild-to-moderate pancytopenia in visceral disease.
Imaging findings depend on organ involvement. Bone radiographs may reveal well-circumscribed lytic lesions or cortical destruction with aggressive periosteal reaction. CT scans may demonstrate hepatosplenomegaly and abdominal lymphadenopathy, with heterogeneous liver parenchyma. Liver biopsy in peliosis hepatica shows dilated, blood-filled cystic spaces within the hepatic parenchyma, often with associated necrosis in advanced cases.
The differential diagnosis includes Kaposi’s sarcoma, pyogenic granulomas, angiomas, and other vascular tumors. Kaposi’s sarcoma may coexist with bacillary angiomatosis and should be considered, particularly if lesions fail to improve with antibiotic therapy.
Treatment begins with evaluation of the extent of organ involvement. First-line therapy consists of erythromycin 500 mg orally every six hours or doxycycline 100 mg orally twice daily. Treatment duration is generally three months for bacillary angiomatosis and four months for peliosis hepatica, with longer courses required in immunocompromised patients. A Jarisch–Herxheimer reaction may occur after initiation of therapy; pretreatment with antipyretics for the first 72 hours may help.
For patients intolerant to first-line therapy, azithromycin or clarithromycin may be used. In severe, life-threatening, or central nervous system disease—particularly in immunocompromised individuals—combination therapy with rifampin added to erythromycin or doxycycline is recommended. TMP-SMX and ciprofloxacin have shown inconsistent results. Most patients can be managed as outpatients, though hospitalization and intravenous therapy are necessary for extensive or fulminant disease.
Clinical improvement is often observed within 4–7 days of therapy, with near-complete resolution of lesions by 3–4 weeks. Relapses occur in approximately 15% of cases and may require prolonged suppressive therapy. Monitoring includes clinical assessment, serial liver function tests in visceral disease, and imaging studies for bone involvement.
Complications of visceral disease include anemia, pancytopenia due to hypersplenism, and splenic rupture with hemoperitoneum. Early recognition and prolonged antimicrobial therapy are essential for favorable outcomes.
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Infectious Disease and Microbiology – Babesiosis
Babesiosis is a protozoal infection caused by Babesia species, intraerythrocytic parasites with a predilection for human red blood cells. It is an important cause of hemolytic disease in endemic regions. The most common species in the United States is Babesia microti, transmitted primarily through the bite of Ixodes (deer) ticks. Less common modes of transmission include blood transfusion and, rarely, congenital (maternal–fetal) transmission. Most cases in the United States occur in the Northeastern and Midwestern regions, while other species such as Babesia divergens (Europe) and Babesia duncani (Western US) are also recognized.
Babesiosis is considered an emerging infectious disease, with increasing reported cases over recent decades. Expansion of deer populations, increased tick density, and greater human exposure to endemic areas contribute to rising incidence. Many infections, especially in younger and immunocompetent individuals, are asymptomatic, leading to underestimation of true prevalence. Serologic surveys in highly endemic areas show that 0.5–15% of blood donors have evidence of prior exposure.
Risk factors include residence in or travel to endemic areas, asplenia, and immunosuppression (e.g., HIV infection or chemotherapy). Preventive strategies focus on avoiding tick exposure, especially during peak transmission months (May through October). Use of insect repellents containing DEET, treatment of clothing with permethrin, daily tick checks after outdoor activity, prompt tick removal (within 24 hours), and examination of pets are recommended. Asplenic and immunocompromised individuals should exercise particular caution in endemic regions.
The life cycle of Babesia involves transmission between Ixodes ticks and vertebrate hosts, primarily white-footed mice. Humans are incidental, “dead-end” hosts and do not contribute to further transmission. After a tick bite, sporozoites enter the bloodstream and invade erythrocytes, where they develop into trophozoites. These replicate asexually to form 2–4 merozoites, which lyse red blood cells and infect additional erythrocytes, resulting in hemolysis and anemia.
Clinical presentation ranges from asymptomatic infection to severe, life-threatening disease. Common symptoms include fever, chills, weakness, headache, nausea, abdominal pain, myalgias, and dark urine. Severe cases may present with shortness of breath or chest pain. A detailed history should include recent travel to endemic areas, tick exposure, outdoor activities, pets, prior Lyme disease, or recent transfusions. Co-infection with Lyme disease or human granulocytic anaplasmosis is common because these infections share the same vector.
On physical examination, patients may have fever, pallor, jaundice, splenomegaly, and hepatomegaly. Lymphadenopathy is typically absent. In cases of Lyme co-infection, erythema migrans rash may be present.
Laboratory findings include anemia and thrombocytopenia on complete blood count, along with laboratory evidence of hemolysis such as elevated reticulocyte count, lactate dehydrogenase (LDH), and indirect bilirubin, and low haptoglobin. Thin peripheral blood smears are the cornerstone of diagnosis and may show intraerythrocytic parasites. Multiple smears over several days may be required in low parasitemia. The characteristic “Maltese cross” tetrad formation is occasionally seen and is pathognomonic when present. Unlike malaria, Babesia organisms may be observed extracellularly in heavy infection. If smears are negative but suspicion remains high, PCR testing for Babesia DNA is recommended. Serologic testing using indirect immunofluorescent antibody assays can support the diagnosis in selected cases. Imaging is usually unnecessary but may confirm splenomegaly or hepatomegaly.
Treatment for uncomplicated B. microti infection consists of oral atovaquone plus azithromycin for 7–10 days. Severe cases, including those with high parasitemia or significant symptoms, are treated with quinine plus clindamycin, administered orally or intravenously. Immunocompromised patients or those with high parasite burdens may require prolonged therapy for at least six weeks, including two weeks after clearance of parasites from blood smears. Asymptomatic immunocompetent individuals with low-level parasitemia for less than three months typically do not require treatment. In severe disease with parasitemia greater than 10% or with complications such as shock or acute respiratory distress syndrome, red blood cell exchange transfusion may be indicated.
Hospitalized patients require daily monitoring of complete blood count and peripheral blood smears to assess hemolysis and parasite burden. Patients should be educated about preventive measures to reduce the risk of reinfection.
Complications of babesiosis include disseminated intravascular coagulation, severe hemolytic anemia, congestive heart failure, acute respiratory distress syndrome, renal dysfunction, and hypotension. Severe disease is more likely in asplenic and immunocompromised individuals.
Babesiosis is a protozoal infection caused by Babesia species, intraerythrocytic parasites with a predilection for human red blood cells. It is an important cause of hemolytic disease in endemic regions. The most common species in the United States is Babesia microti, transmitted primarily through the bite of Ixodes (deer) ticks. Less common modes of transmission include blood transfusion and, rarely, congenital (maternal–fetal) transmission. Most cases in the United States occur in the Northeastern and Midwestern regions, while other species such as Babesia divergens (Europe) and Babesia duncani (Western US) are also recognized.
Babesiosis is considered an emerging infectious disease, with increasing reported cases over recent decades. Expansion of deer populations, increased tick density, and greater human exposure to endemic areas contribute to rising incidence. Many infections, especially in younger and immunocompetent individuals, are asymptomatic, leading to underestimation of true prevalence. Serologic surveys in highly endemic areas show that 0.5–15% of blood donors have evidence of prior exposure.
Risk factors include residence in or travel to endemic areas, asplenia, and immunosuppression (e.g., HIV infection or chemotherapy). Preventive strategies focus on avoiding tick exposure, especially during peak transmission months (May through October). Use of insect repellents containing DEET, treatment of clothing with permethrin, daily tick checks after outdoor activity, prompt tick removal (within 24 hours), and examination of pets are recommended. Asplenic and immunocompromised individuals should exercise particular caution in endemic regions.
The life cycle of Babesia involves transmission between Ixodes ticks and vertebrate hosts, primarily white-footed mice. Humans are incidental, “dead-end” hosts and do not contribute to further transmission. After a tick bite, sporozoites enter the bloodstream and invade erythrocytes, where they develop into trophozoites. These replicate asexually to form 2–4 merozoites, which lyse red blood cells and infect additional erythrocytes, resulting in hemolysis and anemia.
Clinical presentation ranges from asymptomatic infection to severe, life-threatening disease. Common symptoms include fever, chills, weakness, headache, nausea, abdominal pain, myalgias, and dark urine. Severe cases may present with shortness of breath or chest pain. A detailed history should include recent travel to endemic areas, tick exposure, outdoor activities, pets, prior Lyme disease, or recent transfusions. Co-infection with Lyme disease or human granulocytic anaplasmosis is common because these infections share the same vector.
On physical examination, patients may have fever, pallor, jaundice, splenomegaly, and hepatomegaly. Lymphadenopathy is typically absent. In cases of Lyme co-infection, erythema migrans rash may be present.
Laboratory findings include anemia and thrombocytopenia on complete blood count, along with laboratory evidence of hemolysis such as elevated reticulocyte count, lactate dehydrogenase (LDH), and indirect bilirubin, and low haptoglobin. Thin peripheral blood smears are the cornerstone of diagnosis and may show intraerythrocytic parasites. Multiple smears over several days may be required in low parasitemia. The characteristic “Maltese cross” tetrad formation is occasionally seen and is pathognomonic when present. Unlike malaria, Babesia organisms may be observed extracellularly in heavy infection. If smears are negative but suspicion remains high, PCR testing for Babesia DNA is recommended. Serologic testing using indirect immunofluorescent antibody assays can support the diagnosis in selected cases. Imaging is usually unnecessary but may confirm splenomegaly or hepatomegaly.
Treatment for uncomplicated B. microti infection consists of oral atovaquone plus azithromycin for 7–10 days. Severe cases, including those with high parasitemia or significant symptoms, are treated with quinine plus clindamycin, administered orally or intravenously. Immunocompromised patients or those with high parasite burdens may require prolonged therapy for at least six weeks, including two weeks after clearance of parasites from blood smears. Asymptomatic immunocompetent individuals with low-level parasitemia for less than three months typically do not require treatment. In severe disease with parasitemia greater than 10% or with complications such as shock or acute respiratory distress syndrome, red blood cell exchange transfusion may be indicated.
Hospitalized patients require daily monitoring of complete blood count and peripheral blood smears to assess hemolysis and parasite burden. Patients should be educated about preventive measures to reduce the risk of reinfection.
Complications of babesiosis include disseminated intravascular coagulation, severe hemolytic anemia, congestive heart failure, acute respiratory distress syndrome, renal dysfunction, and hypotension. Severe disease is more likely in asplenic and immunocompromised individuals.
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Infectious Disease and Microbiology – Atypical Mycobacteria (Nontuberculous Mycobacteria)
Atypical mycobacteria refer to infections caused by nontuberculous mycobacteria (NTM), a diverse group of environmental mycobacterial species distinct from Mycobacterium tuberculosis. In children, atypical mycobacteria should be considered in cases of unilateral cervical lymphadenitis, particularly in those aged 1–5 years. The swelling typically involves the anterior cervical chain, enlarges gradually, and may form fistulas through the skin. Enlarged lymph nodes are often painless, and systemic symptoms are uncommon. Most pediatric cases are caused by Mycobacterium avium complex (MAC), while M. scrofulaceum and M. tuberculosis are less frequent causes. Approximately 300 cases of MAC lymphadenitis occur annually in the United States. Overall prevalence ranges from 1 to 7.2 cases per 100,000 persons in the US, varying by region, and about half of NTM isolates represent true pathogens.
Risk factors for NTM infection include advanced age, immunosuppression, HIV infection with low CD4 counts, interferon-gamma deficiencies, and underlying structural lung disease such as bronchiectasis or chronic obstructive pulmonary disease. Genetic defects such as IFN-γ receptor 1 (IFNγR1) or interleukin-12 receptor β1 (IL-12βR1) deficiency predispose individuals to disseminated disease. In patients with AIDS and CD4 counts below 100 cells/mm³, primary prophylaxis with weekly azithromycin 1200 mg is recommended; alternatives include clarithromycin or rifabutin.
NTM are widely found in soil and water, including hot tubs and tap water. Human-to-human transmission has not been documented. Infection occurs primarily through ingestion or inhalation rather than reactivation of latent disease. Granuloma formation results from interactions between macrophages, lymphocytes, and natural killer cells. Disseminated infection arises from uncontrolled localized disease, especially in immunocompromised hosts. These organisms are aerobic, non–spore-forming bacilli with mycolic acid–containing cell walls. They are categorized by growth rate into rapid-growing mycobacteria (e.g., M. fortuitum, M. chelonae/abscessus, M. smegmatis), intermediate growers (e.g., M. marinum, M. gordonae), and slow-growing organisms (e.g., MAC, M. kansasii, M. xenopi, M. scrofulaceum, M. haemophilum, M. ulcerans).
Clinical syndromes include pulmonary disease, lymphadenitis, skin and soft tissue infection, osteoarticular disease, catheter-related infection, and disseminated disease. Pulmonary infection typically presents with chronic productive cough and may progress to weight loss, fatigue, dyspnea, hemoptysis, and chest pain. Soft tissue infections often follow trauma, surgery, or aquatic exposure and appear as papular or ulcerative lesions that may spread along lymphatics. Lymphadenitis usually manifests as painless or mildly tender enlargement of submandibular or jugular lymph nodes. Disseminated disease, most commonly seen in advanced HIV infection, presents with fever, fatigue, anorexia, and laboratory abnormalities such as pancytopenia or elevated alkaline phosphatase.
Diagnosis requires correlation of clinical, radiographic, and microbiologic findings because NTM may represent colonization rather than true infection. In pulmonary disease, chest imaging may show upper-lobe cavitary lesions, nodular or reticulonodular infiltrates, or adenopathy. Cavitary disease is common in MAC pulmonary infections and typically involves thin-walled cavities measuring 2–4 cm. At least three sputum samples (or bronchoalveolar lavage specimens) should be obtained for acid-fast bacillus smear and culture. Mycobacterial blood cultures are positive in approximately 90% of disseminated MAC cases. Tissue biopsy demonstrating granulomas with giant cells and acid-fast bacilli supports localized infection, whereas well-formed granulomas may be absent in disseminated disease. Definitive identification and susceptibility testing should be performed at specialized laboratories.
Treatment depends on the species and site of infection and often requires prolonged multidrug therapy. Pulmonary MAC is treated with rifampin, ethambutol, and a macrolide (azithromycin or clarithromycin), sometimes with an aminoglycoside for severe disease. Therapy continues for at least 12 months after cultures become negative. Pulmonary infection with M. kansasii is treated with isoniazid, rifampin, and ethambutol. Rapid-growing mycobacteria causing soft tissue infections are treated with two active agents based on susceptibility testing, such as trimethoprim–sulfamethoxazole, doxycycline, levofloxacin, or clarithromycin. Severe M. abscessus infections may require amikacin combined with clarithromycin and cefoxitin or imipenem. Disseminated MAC in HIV patients is treated with a macrolide plus ethambutol, with consideration of adding rifampin.
Surgical management may be necessary in selected cases. Resection of affected lymph nodes in MAC lymphadenitis achieves cure in approximately 90% of pediatric cases without antimicrobials. Lung resection may be considered in localized refractory pulmonary disease. Incision and drainage are often required for soft tissue infections.
Long-term follow-up is essential because therapy may last months to years and drug toxicities are common. Patients require regular laboratory monitoring, evaluation for drug–drug interactions, and sometimes therapeutic drug monitoring. Prognosis depends on the infecting species, the site of disease, and the host’s immune status. Complications include ulceration and fistula formation in lymphadenitis and, rarely, gastrointestinal complications such as intussusception or obstruction in disseminated MAC.
Atypical mycobacteria refer to infections caused by nontuberculous mycobacteria (NTM), a diverse group of environmental mycobacterial species distinct from Mycobacterium tuberculosis. In children, atypical mycobacteria should be considered in cases of unilateral cervical lymphadenitis, particularly in those aged 1–5 years. The swelling typically involves the anterior cervical chain, enlarges gradually, and may form fistulas through the skin. Enlarged lymph nodes are often painless, and systemic symptoms are uncommon. Most pediatric cases are caused by Mycobacterium avium complex (MAC), while M. scrofulaceum and M. tuberculosis are less frequent causes. Approximately 300 cases of MAC lymphadenitis occur annually in the United States. Overall prevalence ranges from 1 to 7.2 cases per 100,000 persons in the US, varying by region, and about half of NTM isolates represent true pathogens.
Risk factors for NTM infection include advanced age, immunosuppression, HIV infection with low CD4 counts, interferon-gamma deficiencies, and underlying structural lung disease such as bronchiectasis or chronic obstructive pulmonary disease. Genetic defects such as IFN-γ receptor 1 (IFNγR1) or interleukin-12 receptor β1 (IL-12βR1) deficiency predispose individuals to disseminated disease. In patients with AIDS and CD4 counts below 100 cells/mm³, primary prophylaxis with weekly azithromycin 1200 mg is recommended; alternatives include clarithromycin or rifabutin.
NTM are widely found in soil and water, including hot tubs and tap water. Human-to-human transmission has not been documented. Infection occurs primarily through ingestion or inhalation rather than reactivation of latent disease. Granuloma formation results from interactions between macrophages, lymphocytes, and natural killer cells. Disseminated infection arises from uncontrolled localized disease, especially in immunocompromised hosts. These organisms are aerobic, non–spore-forming bacilli with mycolic acid–containing cell walls. They are categorized by growth rate into rapid-growing mycobacteria (e.g., M. fortuitum, M. chelonae/abscessus, M. smegmatis), intermediate growers (e.g., M. marinum, M. gordonae), and slow-growing organisms (e.g., MAC, M. kansasii, M. xenopi, M. scrofulaceum, M. haemophilum, M. ulcerans).
Clinical syndromes include pulmonary disease, lymphadenitis, skin and soft tissue infection, osteoarticular disease, catheter-related infection, and disseminated disease. Pulmonary infection typically presents with chronic productive cough and may progress to weight loss, fatigue, dyspnea, hemoptysis, and chest pain. Soft tissue infections often follow trauma, surgery, or aquatic exposure and appear as papular or ulcerative lesions that may spread along lymphatics. Lymphadenitis usually manifests as painless or mildly tender enlargement of submandibular or jugular lymph nodes. Disseminated disease, most commonly seen in advanced HIV infection, presents with fever, fatigue, anorexia, and laboratory abnormalities such as pancytopenia or elevated alkaline phosphatase.
Diagnosis requires correlation of clinical, radiographic, and microbiologic findings because NTM may represent colonization rather than true infection. In pulmonary disease, chest imaging may show upper-lobe cavitary lesions, nodular or reticulonodular infiltrates, or adenopathy. Cavitary disease is common in MAC pulmonary infections and typically involves thin-walled cavities measuring 2–4 cm. At least three sputum samples (or bronchoalveolar lavage specimens) should be obtained for acid-fast bacillus smear and culture. Mycobacterial blood cultures are positive in approximately 90% of disseminated MAC cases. Tissue biopsy demonstrating granulomas with giant cells and acid-fast bacilli supports localized infection, whereas well-formed granulomas may be absent in disseminated disease. Definitive identification and susceptibility testing should be performed at specialized laboratories.
Treatment depends on the species and site of infection and often requires prolonged multidrug therapy. Pulmonary MAC is treated with rifampin, ethambutol, and a macrolide (azithromycin or clarithromycin), sometimes with an aminoglycoside for severe disease. Therapy continues for at least 12 months after cultures become negative. Pulmonary infection with M. kansasii is treated with isoniazid, rifampin, and ethambutol. Rapid-growing mycobacteria causing soft tissue infections are treated with two active agents based on susceptibility testing, such as trimethoprim–sulfamethoxazole, doxycycline, levofloxacin, or clarithromycin. Severe M. abscessus infections may require amikacin combined with clarithromycin and cefoxitin or imipenem. Disseminated MAC in HIV patients is treated with a macrolide plus ethambutol, with consideration of adding rifampin.
Surgical management may be necessary in selected cases. Resection of affected lymph nodes in MAC lymphadenitis achieves cure in approximately 90% of pediatric cases without antimicrobials. Lung resection may be considered in localized refractory pulmonary disease. Incision and drainage are often required for soft tissue infections.
Long-term follow-up is essential because therapy may last months to years and drug toxicities are common. Patients require regular laboratory monitoring, evaluation for drug–drug interactions, and sometimes therapeutic drug monitoring. Prognosis depends on the infecting species, the site of disease, and the host’s immune status. Complications include ulceration and fistula formation in lymphadenitis and, rarely, gastrointestinal complications such as intussusception or obstruction in disseminated MAC.
