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Infectious disease and microbiology – Myocarditis
Myocarditis is an inflammatory condition of the heart muscle (myocardium) that can result from a wide range of infectious agents, immune-mediated mechanisms, or external toxins. It may occur due to direct infection of cardiac tissue or from an immune response in which antibodies cross-react with myocardial cells, leading to damage. Although relatively uncommon, with an estimated incidence of 1–10 cases per 100,000 individuals, myocarditis is clinically significant because it contributes to up to 12% of sudden cardiac deaths in adolescents and young adults, affecting young males. Its true prevalence is difficult to determine because presentations range from mild, self-limited illness to severe heart failure or sudden death.
The disease is associated with numerous infectious causes, most commonly viral pathogens such as enteroviruses (especially Coxsackie B), adenovirus, influenza, cytomegalovirus, Epstein-Barr virus, HIV, and others. Bacterial, rickettsial, spirochetal, fungal, protozoal, and parasitic infections may also lead to myocarditis. Notably, Trypanosoma cruzi (Chagas disease) and HIV are important contributors in certain populations. Noninfectious triggers such as toxins, drugs, and systemic inflammatory diseases can also play a role. Immunocompromised individuals are at increased risk, and vaccination against viral pathogens may help reduce incidence.
Pathophysiologically, myocardial injury results from a combination of direct cytotoxic effects of pathogens, immune-mediated inflammation, cytokine release (e.g., tumor necrosis factor-alpha), and apoptosis of cardiac cells, all of which impair cardiac function.
Clinically, patients often report a recent viral-like illness with fever, malaise, or respiratory symptoms, followed by chest pain, palpitations, shortness of breath, or syncope. In some cases, myocarditis mimics acute myocardial infarction, while in others it presents later as chronic heart failure. Physical examination may reveal tachycardia, arrhythmias, signs of heart failure, or an S3 gallop, along with systemic features depending on the underlying cause.
Diagnosis involves a combination of laboratory testing, imaging, and sometimes biopsy. Laboratory findings may include leukocytosis, elevated inflammatory markers, and increased cardiac enzymes such as troponin. Imaging studies—especially echocardiography and cardiac MRI—help assess cardiac function and inflammation. Electrocardiography often shows nonspecific changes or conduction abnormalities. The gold standard for diagnosis is endomyocardial biopsy, which demonstrates inflammatory infiltration and myocardial necrosis, although it carries procedural risks and may yield false negatives.
Management is largely supportive, focusing on treatment of heart failure with medications such as diuretics, ACE inhibitors, and beta-blockers. Specific antimicrobial or antiviral therapy is used when an identifiable cause is present. In severe cases, advanced supportive measures such as ventricular assist devices or extracorporeal membrane oxygenation may be required, and cardiac transplantation may be considered in refractory cases. Adjunctive therapies such as intravenous immunoglobulin or immunosuppressive agents may be used selectively.
Follow-up care includes gradual rehabilitation, serial cardiac monitoring, and repeat imaging, with restrictions on physical activity during recovery. Long-term outcomes vary: some patients recover completely, while others develop complications such as dilated cardiomyopathy, arrhythmias, heart block, or cardiogenic shock. Early recognition and appropriate management are essential to improve prognosis and reduce the risk of serious complications, including sudden cardiac death.
Myocarditis is an inflammatory condition of the heart muscle (myocardium) that can result from a wide range of infectious agents, immune-mediated mechanisms, or external toxins. It may occur due to direct infection of cardiac tissue or from an immune response in which antibodies cross-react with myocardial cells, leading to damage. Although relatively uncommon, with an estimated incidence of 1–10 cases per 100,000 individuals, myocarditis is clinically significant because it contributes to up to 12% of sudden cardiac deaths in adolescents and young adults, affecting young males. Its true prevalence is difficult to determine because presentations range from mild, self-limited illness to severe heart failure or sudden death.
The disease is associated with numerous infectious causes, most commonly viral pathogens such as enteroviruses (especially Coxsackie B), adenovirus, influenza, cytomegalovirus, Epstein-Barr virus, HIV, and others. Bacterial, rickettsial, spirochetal, fungal, protozoal, and parasitic infections may also lead to myocarditis. Notably, Trypanosoma cruzi (Chagas disease) and HIV are important contributors in certain populations. Noninfectious triggers such as toxins, drugs, and systemic inflammatory diseases can also play a role. Immunocompromised individuals are at increased risk, and vaccination against viral pathogens may help reduce incidence.
Pathophysiologically, myocardial injury results from a combination of direct cytotoxic effects of pathogens, immune-mediated inflammation, cytokine release (e.g., tumor necrosis factor-alpha), and apoptosis of cardiac cells, all of which impair cardiac function.
Clinically, patients often report a recent viral-like illness with fever, malaise, or respiratory symptoms, followed by chest pain, palpitations, shortness of breath, or syncope. In some cases, myocarditis mimics acute myocardial infarction, while in others it presents later as chronic heart failure. Physical examination may reveal tachycardia, arrhythmias, signs of heart failure, or an S3 gallop, along with systemic features depending on the underlying cause.
Diagnosis involves a combination of laboratory testing, imaging, and sometimes biopsy. Laboratory findings may include leukocytosis, elevated inflammatory markers, and increased cardiac enzymes such as troponin. Imaging studies—especially echocardiography and cardiac MRI—help assess cardiac function and inflammation. Electrocardiography often shows nonspecific changes or conduction abnormalities. The gold standard for diagnosis is endomyocardial biopsy, which demonstrates inflammatory infiltration and myocardial necrosis, although it carries procedural risks and may yield false negatives.
Management is largely supportive, focusing on treatment of heart failure with medications such as diuretics, ACE inhibitors, and beta-blockers. Specific antimicrobial or antiviral therapy is used when an identifiable cause is present. In severe cases, advanced supportive measures such as ventricular assist devices or extracorporeal membrane oxygenation may be required, and cardiac transplantation may be considered in refractory cases. Adjunctive therapies such as intravenous immunoglobulin or immunosuppressive agents may be used selectively.
Follow-up care includes gradual rehabilitation, serial cardiac monitoring, and repeat imaging, with restrictions on physical activity during recovery. Long-term outcomes vary: some patients recover completely, while others develop complications such as dilated cardiomyopathy, arrhythmias, heart block, or cardiogenic shock. Early recognition and appropriate management are essential to improve prognosis and reduce the risk of serious complications, including sudden cardiac death.
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Infectious disease and microbiology – Myelitis
Myelitis is an inflammatory condition of the spinal cord caused by infection or involvement of adjacent tissues, leading to neurologic dysfunction affecting motor, sensory, and autonomic systems.
The epidemiology varies widely depending on the underlying infectious cause. It can occur in both immunocompetent and immunocompromised individuals, although the latter are at higher risk.
Risk Factors
Inflammation may involve:
Etiology
A wide range of infectious agents can cause myelitis:
Viral causes (most common):
History:
Transverse Myelitis:
Laboratory Tests:
Noninfectious causes include:
Targeted antimicrobial therapy based on cause:
Myelitis is an inflammatory condition of the spinal cord caused by infection or involvement of adjacent tissues, leading to neurologic dysfunction affecting motor, sensory, and autonomic systems.
The epidemiology varies widely depending on the underlying infectious cause. It can occur in both immunocompetent and immunocompromised individuals, although the latter are at higher risk.
Risk Factors
- Immunocompromised state (e.g., HIV, malignancy, steroid use)
- Vaccination against poliomyelitis and varicella-zoster virus (VZV)
Inflammation may involve:
- Entire cross-section of the spinal cord → transverse myelitis
- Focal segments → localized myelitis
- Nerve roots involvement → radiculomyelitis
Etiology
A wide range of infectious agents can cause myelitis:
Viral causes (most common):
- Herpes viruses (HSV, EBV, VZV, CMV, HHV-6)
- HIV (vacuolar myelopathy)
- HTLV-1 (tropical spastic paraparesis)
- Influenza virus
- Enteroviruses (coxsackie, echovirus, enterovirus 70/71)
- West Nile virus
- Mycoplasma pneumoniae
- Lyme disease (Borrelia burgdorferi)
- Syphilis (posterior column involvement – tabes dorsalis)
- Tuberculosis (spondylitis, tuberculomas)
- Leptospirosis
- Aspergillus, Coccidioides, Blastomyces
- Schistosomiasis
- Neurocysticercosis
- Epidural abscess causing spinal cord compression
History:
- Rapid onset (hours to days)
- Motor weakness (often bilateral)
- Sensory disturbances
- Bladder and bowel dysfunction
- Back pain or radicular (dermatomal) pain
Transverse Myelitis:
- Sensory level on the trunk
- Loss of motor and sensory function below lesion
- Reflexes initially decreased, later hyperactive
- Asymmetric weakness
- Fasciculations and muscle atrophy
- Loss of reflexes (lower motor neuron signs)
- Dermatomal pain and sensory loss
- Ipsilateral to rash
- Motor involvement is less common
Laboratory Tests:
- CSF analysis:
- Cell count, glucose, protein
- PCR for HSV, CMV, VZV
- West Nile virus IgM
- VDRL (for syphilis)
- Serology for HIV, Lyme disease, enteroviruses
- Normal glucose (viral causes)
- Elevated protein
- Lymphocytic predominance (except early herpes infections)
- MRI of the spine shows focal or diffuse enhancing lesions
- Inflammatory infiltration (lymphocytes, monocytes)
- Demyelination and axonal injury
Noninfectious causes include:
- Multiple sclerosis
- Vitamin B12 deficiency
- Autoimmune diseases (e.g., SLE)
- Neurosarcoidosis
- Paraneoplastic syndromes
Targeted antimicrobial therapy based on cause:
- HSV → Acyclovir
- CMV → Ganciclovir or foscarnet
- HIV → Antiretroviral therapy
- Other infections → Etiology-specific treatment
- Corticosteroids (e.g., IV methylprednisolone) are often used, though their benefit remains uncertain
- Emergency decompression if spinal cord compression (e.g., epidural abscess) is present
- Patients often require rehabilitation and neurologic follow-up
- Relapses may occur depending on etiology
- Chronic neuropathic pain
- Partial or complete paralysis
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Infectious disease and microbiology – Mycotic aneurysms
Mycotic aneurysms are infected aneurysms of blood vessels that arise as part of an infectious process, most commonly infective endocarditis (IE). Despite the name, “mycotic” refers to the fungus-like shape of the aneurysm, not the cause, which is usually bacterial.
These aneurysms may be intracranial or extracranial, and they can also occur due to infection of a preexisting aneurysm or arterial wall (microbial arteritis).
Epidemiologically, about 2–4% of patients with infective endocarditis develop intracranial mycotic aneurysms, although the true incidence is likely underestimated due to asymptomatic cases. The prevalence in the general population is unknown but has decreased in the antibiotic era.
Major risk factors include:
Clinically, many patients are asymptomatic until complications occur.
Symptoms depend on location:
Diagnosis relies on a combination of laboratory tests and imaging.
Treatment involves prolonged intravenous antibiotics (at least 6–8 weeks) tailored to the identified organism.
Some patients, especially those with intracranial aneurysms, may improve with antibiotics alone.
Surgical or endovascular intervention is required in cases of:
The prognosis is serious, with mortality depending on rupture status:
Mycotic aneurysms are infected aneurysms of blood vessels that arise as part of an infectious process, most commonly infective endocarditis (IE). Despite the name, “mycotic” refers to the fungus-like shape of the aneurysm, not the cause, which is usually bacterial.
These aneurysms may be intracranial or extracranial, and they can also occur due to infection of a preexisting aneurysm or arterial wall (microbial arteritis).
Epidemiologically, about 2–4% of patients with infective endocarditis develop intracranial mycotic aneurysms, although the true incidence is likely underestimated due to asymptomatic cases. The prevalence in the general population is unknown but has decreased in the antibiotic era.
Major risk factors include:
- Infective endocarditis
- Intravenous drug use
- Arterial trauma
- Contiguous infections near blood vessels
- Immunosuppression and advanced age
- Septic emboli from cardiac vegetations lodging in vessels
- Bacteremic seeding of damaged arterial intima
- Direct spread from nearby infections
- Direct inoculation from trauma or procedures
Clinically, many patients are asymptomatic until complications occur.
Symptoms depend on location:
- Intracranial aneurysms: headache, fever, stroke-like symptoms, seizures
- Aortic aneurysms: abdominal or back pain, fever
- Rupture: sudden deterioration, bleeding, shock
Diagnosis relies on a combination of laboratory tests and imaging.
- Blood cultures are positive in 50–85% of cases
- Elevated white blood cell count and anemia are common
- Conventional angiography is the gold standard
- CT, MRI, and Doppler ultrasound help localize and assess the aneurysm
Treatment involves prolonged intravenous antibiotics (at least 6–8 weeks) tailored to the identified organism.
Some patients, especially those with intracranial aneurysms, may improve with antibiotics alone.
Surgical or endovascular intervention is required in cases of:
- Rupture or bleeding
- Enlarging aneurysm despite therapy
- High-risk anatomical locations
The prognosis is serious, with mortality depending on rupture status:
- ~30% mortality if aneurysm is intact
- Up to 80% mortality if rupture occurs
- Hemorrhage (e.g., subarachnoid hemorrhage)
- Embolization
- Vascular insufficiency
- Shock and death
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Infectious disease and microbiology – Mumps
Mumps is a viral infection primarily affecting children, characterized by painful swelling of the parotid glands. Although usually mild and self-limited, it can lead to complications such as orchitis, pancreatitis, and aseptic meningitis, especially in adults.
The disease occurs worldwide and is caused by an enveloped RNA virus from the Paramyxoviridae family (genus Rubulavirus). Transmission occurs through direct contact with respiratory secretions of infected individuals.
Mumps most commonly affects children aged 5–9 years, although about one-third of cases occur in individuals older than 15 years. Widespread vaccination programs have significantly reduced incidence, particularly in developed countries. However, outbreaks can still occur, especially in crowded settings such as college campuses, even among vaccinated populations.
The incubation period ranges from 14 to 21 days, and up to 30–40% of infections may be asymptomatic. Symptomatic patients typically present with fever, malaise, headache, and painful swelling of the parotid glands, which develops within the first few days. Swelling is often bilateral and may be worsened by eating sour foods. Symptoms usually resolve within one week.
On physical examination, parotid enlargement leads to obliteration of the mandibular angle and upward displacement of the ear. Other salivary glands may occasionally be involved.
Complications can occur, particularly in post-pubertal individuals.
Orchitis affects up to 30% of post-pubertal males, presenting with testicular pain, swelling, and fever.
In females, oophoritis and mastitis may occur.
Aseptic meningitis is relatively common but typically self-limited.
Other complications include transient hearing loss, pancreatitis, and rarely encephalitis.
Diagnosis is usually clinical, based on characteristic features. Laboratory findings may include leukopenia and elevated serum amylase.
Confirmation can be achieved with serologic testing (IgM/IgG ELISA) or PCR detection of viral RNA from saliva, cerebrospinal fluid, or urine.
There is no specific antiviral treatment for mumps. Management is supportive and includes rest, hydration, and analgesics.
In cases of orchitis, additional measures such as scrotal elevation, cold compresses, and NSAIDs are recommended.
Prevention relies on vaccination, typically given as part of the MMR (measles–mumps–rubella) vaccine, administered in childhood with two doses. Isolation of infected individuals for 5 days after onset of parotitis helps limit transmission.
The prognosis is generally excellent, with lifelong immunity after infection.
Complications are uncommon but may include testicular atrophy, reduced sperm counts, hearing loss, encephalitis, and, rarely, permanent neurologic damage.
In pregnancy, mumps infection has been associated with fetal complications, including low birth weight and fetal loss.
Mumps is a viral infection primarily affecting children, characterized by painful swelling of the parotid glands. Although usually mild and self-limited, it can lead to complications such as orchitis, pancreatitis, and aseptic meningitis, especially in adults.
The disease occurs worldwide and is caused by an enveloped RNA virus from the Paramyxoviridae family (genus Rubulavirus). Transmission occurs through direct contact with respiratory secretions of infected individuals.
Mumps most commonly affects children aged 5–9 years, although about one-third of cases occur in individuals older than 15 years. Widespread vaccination programs have significantly reduced incidence, particularly in developed countries. However, outbreaks can still occur, especially in crowded settings such as college campuses, even among vaccinated populations.
The incubation period ranges from 14 to 21 days, and up to 30–40% of infections may be asymptomatic. Symptomatic patients typically present with fever, malaise, headache, and painful swelling of the parotid glands, which develops within the first few days. Swelling is often bilateral and may be worsened by eating sour foods. Symptoms usually resolve within one week.
On physical examination, parotid enlargement leads to obliteration of the mandibular angle and upward displacement of the ear. Other salivary glands may occasionally be involved.
Complications can occur, particularly in post-pubertal individuals.
Orchitis affects up to 30% of post-pubertal males, presenting with testicular pain, swelling, and fever.
In females, oophoritis and mastitis may occur.
Aseptic meningitis is relatively common but typically self-limited.
Other complications include transient hearing loss, pancreatitis, and rarely encephalitis.
Diagnosis is usually clinical, based on characteristic features. Laboratory findings may include leukopenia and elevated serum amylase.
Confirmation can be achieved with serologic testing (IgM/IgG ELISA) or PCR detection of viral RNA from saliva, cerebrospinal fluid, or urine.
There is no specific antiviral treatment for mumps. Management is supportive and includes rest, hydration, and analgesics.
In cases of orchitis, additional measures such as scrotal elevation, cold compresses, and NSAIDs are recommended.
Prevention relies on vaccination, typically given as part of the MMR (measles–mumps–rubella) vaccine, administered in childhood with two doses. Isolation of infected individuals for 5 days after onset of parotitis helps limit transmission.
The prognosis is generally excellent, with lifelong immunity after infection.
Complications are uncommon but may include testicular atrophy, reduced sperm counts, hearing loss, encephalitis, and, rarely, permanent neurologic damage.
In pregnancy, mumps infection has been associated with fetal complications, including low birth weight and fetal loss.
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Infectious disease and microbiology – Mucormycosis
Mucormycosis is a life-threatening opportunistic fungal infection characterized by vascular invasion, thrombosis, and extensive tissue necrosis. It primarily affects immunocompromised individuals, particularly those with uncontrolled diabetes or hematologic malignancies.
The disease is relatively rare, with an estimated incidence of 1.7 cases per million people annually in the United States, but it carries a very high mortality rate. It occurs worldwide and is increasingly recognized in patients receiving antifungal prophylaxis that does not cover Mucorales (e.g., voriconazole).
Major risk factors include uncontrolled diabetes mellitus (especially with ketoacidosis), hematologic malignancies, organ transplantation, prolonged neutropenia, chronic steroid use, deferoxamine therapy, burns, trauma, and intravenous drug use. HIV infection and malnutrition also predispose to disease. Nosocomial outbreaks have been reported, particularly due to contaminated dressings.
Infection occurs through inhalation, ingestion, or direct inoculation of fungal spores. Once inside the host, Mucorales organisms invade blood vessels, leading to thrombosis, infarction, and necrosis, with rapid spread to adjacent tissues and possible hematogenous dissemination.
The most common causative organisms are molds from the order Mucorales, including Rhizopus, Mucor, Rhizomucor, Absidia, Cunninghamella, and Saksenaea. These fungi are ubiquitous in the environment, especially in soil and decaying organic matter.
Clinical presentation varies depending on the site of infection but is typically rapidly progressive and severe.
Rhinocerebral (craniofacial) mucormycosis, most common in diabetics, begins in the sinuses and spreads to the orbit and brain. Patients may present with facial pain, nasal congestion, black necrotic lesions on the palate or nasal mucosa, orbital swelling, vision loss, and altered mental status.
Pulmonary mucormycosis occurs mainly in neutropenic patients and presents with fever, progressive lung infiltrates, and poor response to antibiotics.
Gastrointestinal mucormycosis is more common in malnourished children and presents with abdominal pain, bleeding, or perforation.
Cutaneous mucormycosis occurs after trauma or burns and presents with necrotic ulcers, eschars, and tissue destruction.
Disseminated disease may involve the brain, liver, spleen, or heart and carries a very poor prognosis.
Diagnosis relies on early clinical suspicion and histopathological confirmation. Microscopy shows broad, nonseptate, irregularly branching hyphae. Culture may be performed from tissue samples, and imaging (CT or MRI) helps assess the extent of disease. Unlike other fungal infections, β-D-glucan tests are not useful.
Treatment requires urgent, aggressive management.
First-line therapy includes intravenous amphotericin B (liposomal formulation preferred due to lower toxicity).
Second-line or salvage therapy includes posaconazole, sometimes used in combination regimens.
Equally important are reversal of underlying risk factors (e.g., control of diabetes, reduction of immunosuppression) and prompt surgical debridement of necrotic tissue, which is often lifesaving.
Additional supportive therapies may include granulocyte transfusions, growth factors, hyperbaric oxygen therapy, and iron chelation strategies in selected cases.
The prognosis remains poor, especially if diagnosis is delayed. Untreated rhinocerebral disease is almost universally fatal within days, while even with treatment, survival in diabetic patients is approximately 50%. Outcomes are worse in immunocompromised individuals and in disseminated disease.
Complications include vascular thrombosis, brain abscesses, pulmonary dissemination, bowel infarction, hemorrhage, and widespread tissue destruction, often leading to death if not rapidly treated.
Mucormycosis is a life-threatening opportunistic fungal infection characterized by vascular invasion, thrombosis, and extensive tissue necrosis. It primarily affects immunocompromised individuals, particularly those with uncontrolled diabetes or hematologic malignancies.
The disease is relatively rare, with an estimated incidence of 1.7 cases per million people annually in the United States, but it carries a very high mortality rate. It occurs worldwide and is increasingly recognized in patients receiving antifungal prophylaxis that does not cover Mucorales (e.g., voriconazole).
Major risk factors include uncontrolled diabetes mellitus (especially with ketoacidosis), hematologic malignancies, organ transplantation, prolonged neutropenia, chronic steroid use, deferoxamine therapy, burns, trauma, and intravenous drug use. HIV infection and malnutrition also predispose to disease. Nosocomial outbreaks have been reported, particularly due to contaminated dressings.
Infection occurs through inhalation, ingestion, or direct inoculation of fungal spores. Once inside the host, Mucorales organisms invade blood vessels, leading to thrombosis, infarction, and necrosis, with rapid spread to adjacent tissues and possible hematogenous dissemination.
The most common causative organisms are molds from the order Mucorales, including Rhizopus, Mucor, Rhizomucor, Absidia, Cunninghamella, and Saksenaea. These fungi are ubiquitous in the environment, especially in soil and decaying organic matter.
Clinical presentation varies depending on the site of infection but is typically rapidly progressive and severe.
Rhinocerebral (craniofacial) mucormycosis, most common in diabetics, begins in the sinuses and spreads to the orbit and brain. Patients may present with facial pain, nasal congestion, black necrotic lesions on the palate or nasal mucosa, orbital swelling, vision loss, and altered mental status.
Pulmonary mucormycosis occurs mainly in neutropenic patients and presents with fever, progressive lung infiltrates, and poor response to antibiotics.
Gastrointestinal mucormycosis is more common in malnourished children and presents with abdominal pain, bleeding, or perforation.
Cutaneous mucormycosis occurs after trauma or burns and presents with necrotic ulcers, eschars, and tissue destruction.
Disseminated disease may involve the brain, liver, spleen, or heart and carries a very poor prognosis.
Diagnosis relies on early clinical suspicion and histopathological confirmation. Microscopy shows broad, nonseptate, irregularly branching hyphae. Culture may be performed from tissue samples, and imaging (CT or MRI) helps assess the extent of disease. Unlike other fungal infections, β-D-glucan tests are not useful.
Treatment requires urgent, aggressive management.
First-line therapy includes intravenous amphotericin B (liposomal formulation preferred due to lower toxicity).
Second-line or salvage therapy includes posaconazole, sometimes used in combination regimens.
Equally important are reversal of underlying risk factors (e.g., control of diabetes, reduction of immunosuppression) and prompt surgical debridement of necrotic tissue, which is often lifesaving.
Additional supportive therapies may include granulocyte transfusions, growth factors, hyperbaric oxygen therapy, and iron chelation strategies in selected cases.
The prognosis remains poor, especially if diagnosis is delayed. Untreated rhinocerebral disease is almost universally fatal within days, while even with treatment, survival in diabetic patients is approximately 50%. Outcomes are worse in immunocompromised individuals and in disseminated disease.
Complications include vascular thrombosis, brain abscesses, pulmonary dissemination, bowel infarction, hemorrhage, and widespread tissue destruction, often leading to death if not rapidly treated.
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Infectious disease and microbiology – Mites (including chiggers)
Mites and chiggers are arthropods with four pairs of legs that infest humans, causing primarily cutaneous disease, but in some cases transmitting systemic infections such as scrub typhus.
The most important human mite is Sarcoptes scabiei, which causes scabies, while chiggers (larval forms of trombiculid mites) are responsible for intensely pruritic skin lesions and can transmit Orientia tsutsugamushi, the causative agent of scrub typhus.
Scabies has a worldwide distribution, with an estimated 300 million cases annually, and is more prevalent in tropical and resource-limited settings. Transmission occurs through close personal contact, including sexual contact, and less commonly via fomites. Household transmission rates can be high, especially in severe forms such as Norwegian (crusted) scabies, where mite burden is extensive.
Scrub typhus is endemic within the “tsutsugamushi triangle” (northern Japan to northern Australia and Afghanistan) and is commonly seen in rural areas, particularly among farmers and individuals exposed to vegetation.
The pathophysiology of scabies involves burrowing of mites into the skin, where they lay eggs. The resulting hypersensitivity reaction to the mites, eggs, and feces causes intense itching and inflammation.
In scrub typhus, the organism causes perivasculitis of small blood vessels, leading to systemic illness and potential multiorgan involvement.
Clinically, scabies presents with intensely pruritic papules and characteristic linear burrows, often found in the web spaces of fingers, wrists, and genital areas. Norwegian scabies, seen in immunocompromised individuals, presents with widespread crusted, hyperkeratotic lesions, which may resemble psoriasis and may not be itchy, leading to delayed diagnosis.
Chigger bites cause erythematous papules or pustules, commonly located around the ankles or waistline, appearing within hours of exposure.
Scrub typhus typically presents with fever, headache, and systemic symptoms, and is characterized by the presence of an eschar—a black necrotic scab—usually found in areas where clothing is tight, such as the groin or waist. Severe cases may progress to ARDS, renal failure, or hepatic dysfunction.
Diagnosis of scabies is primarily clinical, based on characteristic lesions and distribution.
Scrub typhus is diagnosed using serologic testing (IgM ELISA), with laboratory findings that may include thrombocytopenia, lymphocyte changes, and elevated liver enzymes. Chest imaging may be required if respiratory complications are suspected.
Treatment depends on the specific condition.
Scabies is treated with permethrin 5% cream, applied over the entire body and repeated after one week. Oral ivermectin is an alternative. Antihistamines may help relieve itching.
Norwegian scabies requires more aggressive and repeated therapy, often combining topical agents and systemic treatment.
Chigger bites are managed symptomatically with antihistamines or topical steroids.
Scrub typhus is treated with doxycycline, which is highly effective, while azithromycin is preferred in children and pregnant patients.
Preventive measures include good hygiene, contact precautions, and treatment of close contacts in scabies cases. For scrub typhus, protective clothing and insect repellents are essential in endemic areas.
The prognosis is generally excellent with treatment. However, untreated scrub typhus can have a mortality rate of 3–30%, especially when diagnosis is delayed.
Complications may include secondary bacterial skin infections in scabies.
In scrub typhus, severe complications include acute respiratory distress syndrome, renal failure, hepatitis, myocarditis, disseminated intravascular coagulation, meningoencephalitis, and hearing loss.
Mites and chiggers are arthropods with four pairs of legs that infest humans, causing primarily cutaneous disease, but in some cases transmitting systemic infections such as scrub typhus.
The most important human mite is Sarcoptes scabiei, which causes scabies, while chiggers (larval forms of trombiculid mites) are responsible for intensely pruritic skin lesions and can transmit Orientia tsutsugamushi, the causative agent of scrub typhus.
Scabies has a worldwide distribution, with an estimated 300 million cases annually, and is more prevalent in tropical and resource-limited settings. Transmission occurs through close personal contact, including sexual contact, and less commonly via fomites. Household transmission rates can be high, especially in severe forms such as Norwegian (crusted) scabies, where mite burden is extensive.
Scrub typhus is endemic within the “tsutsugamushi triangle” (northern Japan to northern Australia and Afghanistan) and is commonly seen in rural areas, particularly among farmers and individuals exposed to vegetation.
The pathophysiology of scabies involves burrowing of mites into the skin, where they lay eggs. The resulting hypersensitivity reaction to the mites, eggs, and feces causes intense itching and inflammation.
In scrub typhus, the organism causes perivasculitis of small blood vessels, leading to systemic illness and potential multiorgan involvement.
Clinically, scabies presents with intensely pruritic papules and characteristic linear burrows, often found in the web spaces of fingers, wrists, and genital areas. Norwegian scabies, seen in immunocompromised individuals, presents with widespread crusted, hyperkeratotic lesions, which may resemble psoriasis and may not be itchy, leading to delayed diagnosis.
Chigger bites cause erythematous papules or pustules, commonly located around the ankles or waistline, appearing within hours of exposure.
Scrub typhus typically presents with fever, headache, and systemic symptoms, and is characterized by the presence of an eschar—a black necrotic scab—usually found in areas where clothing is tight, such as the groin or waist. Severe cases may progress to ARDS, renal failure, or hepatic dysfunction.
Diagnosis of scabies is primarily clinical, based on characteristic lesions and distribution.
Scrub typhus is diagnosed using serologic testing (IgM ELISA), with laboratory findings that may include thrombocytopenia, lymphocyte changes, and elevated liver enzymes. Chest imaging may be required if respiratory complications are suspected.
Treatment depends on the specific condition.
Scabies is treated with permethrin 5% cream, applied over the entire body and repeated after one week. Oral ivermectin is an alternative. Antihistamines may help relieve itching.
Norwegian scabies requires more aggressive and repeated therapy, often combining topical agents and systemic treatment.
Chigger bites are managed symptomatically with antihistamines or topical steroids.
Scrub typhus is treated with doxycycline, which is highly effective, while azithromycin is preferred in children and pregnant patients.
Preventive measures include good hygiene, contact precautions, and treatment of close contacts in scabies cases. For scrub typhus, protective clothing and insect repellents are essential in endemic areas.
The prognosis is generally excellent with treatment. However, untreated scrub typhus can have a mortality rate of 3–30%, especially when diagnosis is delayed.
Complications may include secondary bacterial skin infections in scabies.
In scrub typhus, severe complications include acute respiratory distress syndrome, renal failure, hepatitis, myocarditis, disseminated intravascular coagulation, meningoencephalitis, and hearing loss.
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Infectious Disease and Microbiology – Mesenteric Adenitis
Mesenteric adenitis is an acute inflammation of the mesenteric lymph nodes, most commonly presenting with symptoms that closely mimic acute appendicitis. It may occur as a primary condition or secondary to other diseases such as Crohn’s disease, infectious colitis, appendicitis, diverticulitis, or systemic lupus erythematosus. In many cases, it is preceded or accompanied by enterocolitis.
It is most commonly seen in children aged 5–14 years and may account for up to 8% of hospital admissions initially suspected to be appendicitis. Although many infections are subclinical or mild, outbreaks have been associated with specific food exposures, particularly undercooked pork, unpasteurized milk, and contaminated food products. Intrafamilial transmission and rare cases linked to blood transfusion have also been reported.
The condition typically results from a gastrointestinal infection, most often involving Yersinia enterocolitica. The pathogen invades Peyer’s patches in the ileum and spreads to mesenteric lymph nodes, causing inflammation. Other infectious causes include Yersinia pseudotuberculosis, Salmonella, and Mycobacterium tuberculosis. Less commonly, viral agents such as Epstein–Barr virus or adenovirus may be involved.
Patients usually present with right lower quadrant abdominal pain and fever, making differentiation from appendicitis challenging. Associated symptoms often include diarrhea and nausea, while vomiting is less common. A history of recent ingestion of high-risk foods within 1–2 weeks prior to symptom onset may provide a clue. On examination, patients may appear acutely ill with localized tenderness in the right lower abdomen. Rebound tenderness can occur but is generally less pronounced than in appendicitis. Occasionally, immune-mediated complications such as erythema nodosum or reactive arthritis may develop, especially in individuals with HLA-B27.
Laboratory findings are nonspecific and may show elevated white blood cell counts, and stool studies may reveal leukocytes in cases with diarrhea. Diagnosis is primarily supported by imaging. Abdominal ultrasound is especially useful in children, demonstrating a normal appendix along with enlarged mesenteric lymph nodes. In adults, CT scanning can confirm the presence of clustered lymph nodes near the ileocecal region while excluding appendicitis. Stool cultures for Yersinia may require special techniques such as cold enrichment, and serologic tests can assist during outbreaks.
Mesenteric adenitis is usually a self-limited condition, and treatment is primarily supportive, including hydration and symptomatic care. Antibiotics are generally not required unless there is confirmed bacterial infection with significant symptoms. In such cases, trimethoprim-sulfamethoxazole is commonly used in children, while adults may receive trimethoprim-sulfamethoxazole or ciprofloxacin. Other antibiotic options include doxycycline, ampicillin, or aminoglycosides in selected cases.
Surgical consultation may be necessary when appendicitis cannot be excluded, and laparoscopy may be performed in uncertain cases. Hospital admission is indicated for patients with severe abdominal pain, fever, rebound tenderness, hypotension, or inability to tolerate oral intake.
The prognosis is excellent, as most cases resolve without complications. However, rare complications can occur, particularly in immunocompromised individuals. These include bacteremia, septic shock, intestinal necrosis, perforation, intussusception, and metastatic infections. Post-infectious immune conditions such as reactive arthritis, uveitis, nephritis, and erythema nodosum may also develop.
Mesenteric adenitis is an acute inflammation of the mesenteric lymph nodes, most commonly presenting with symptoms that closely mimic acute appendicitis. It may occur as a primary condition or secondary to other diseases such as Crohn’s disease, infectious colitis, appendicitis, diverticulitis, or systemic lupus erythematosus. In many cases, it is preceded or accompanied by enterocolitis.
It is most commonly seen in children aged 5–14 years and may account for up to 8% of hospital admissions initially suspected to be appendicitis. Although many infections are subclinical or mild, outbreaks have been associated with specific food exposures, particularly undercooked pork, unpasteurized milk, and contaminated food products. Intrafamilial transmission and rare cases linked to blood transfusion have also been reported.
The condition typically results from a gastrointestinal infection, most often involving Yersinia enterocolitica. The pathogen invades Peyer’s patches in the ileum and spreads to mesenteric lymph nodes, causing inflammation. Other infectious causes include Yersinia pseudotuberculosis, Salmonella, and Mycobacterium tuberculosis. Less commonly, viral agents such as Epstein–Barr virus or adenovirus may be involved.
Patients usually present with right lower quadrant abdominal pain and fever, making differentiation from appendicitis challenging. Associated symptoms often include diarrhea and nausea, while vomiting is less common. A history of recent ingestion of high-risk foods within 1–2 weeks prior to symptom onset may provide a clue. On examination, patients may appear acutely ill with localized tenderness in the right lower abdomen. Rebound tenderness can occur but is generally less pronounced than in appendicitis. Occasionally, immune-mediated complications such as erythema nodosum or reactive arthritis may develop, especially in individuals with HLA-B27.
Laboratory findings are nonspecific and may show elevated white blood cell counts, and stool studies may reveal leukocytes in cases with diarrhea. Diagnosis is primarily supported by imaging. Abdominal ultrasound is especially useful in children, demonstrating a normal appendix along with enlarged mesenteric lymph nodes. In adults, CT scanning can confirm the presence of clustered lymph nodes near the ileocecal region while excluding appendicitis. Stool cultures for Yersinia may require special techniques such as cold enrichment, and serologic tests can assist during outbreaks.
Mesenteric adenitis is usually a self-limited condition, and treatment is primarily supportive, including hydration and symptomatic care. Antibiotics are generally not required unless there is confirmed bacterial infection with significant symptoms. In such cases, trimethoprim-sulfamethoxazole is commonly used in children, while adults may receive trimethoprim-sulfamethoxazole or ciprofloxacin. Other antibiotic options include doxycycline, ampicillin, or aminoglycosides in selected cases.
Surgical consultation may be necessary when appendicitis cannot be excluded, and laparoscopy may be performed in uncertain cases. Hospital admission is indicated for patients with severe abdominal pain, fever, rebound tenderness, hypotension, or inability to tolerate oral intake.
The prognosis is excellent, as most cases resolve without complications. However, rare complications can occur, particularly in immunocompromised individuals. These include bacteremia, septic shock, intestinal necrosis, perforation, intussusception, and metastatic infections. Post-infectious immune conditions such as reactive arthritis, uveitis, nephritis, and erythema nodosum may also develop.
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Infectious Disease and Microbiology - Acute Meningitis
Acute meningitis is a rapidly developing inflammation of the meninges that typically evolves over hours to days. It may resolve spontaneously in viral cases or require urgent treatment when bacterial in origin. Despite advances in therapy, it remains a medical emergency due to its potential for rapid deterioration and severe complications.
Meningitis occurs worldwide and can affect individuals of all ages, including previously healthy people. The overall incidence in the United States is approximately 2–10 cases per 100,000 population annually, with significantly higher rates in neonates and young children. Among bacterial causes, Neisseria meningitidis is unique in its ability to cause epidemics. Vaccination programs have significantly reduced cases of Haemophilus influenzae type B meningitis.
Risk factors include extremes of age, crowded living conditions, close contact with infected individuals, head trauma, neurosurgical devices (e.g., shunts), immunosuppression, and chronic illnesses. Specific conditions predispose to certain pathogens—for example, asplenia increases risk for pneumococcal and meningococcal infections, while complement deficiencies increase susceptibility to meningococcal disease. Tick exposure may lead to Lyme meningitis.
The pathogenesis begins with colonization of the nasopharynx, followed by invasion into the bloodstream and crossing of the blood–brain barrier into the cerebrospinal fluid (CSF), where pathogens multiply. Inflammation in the subarachnoid space leads to increased intracranial pressure and neurologic dysfunction.
Etiologically, most cases are viral, particularly due to enteroviruses. However, bacterial meningitis is more severe and commonly caused by Streptococcus pneumoniae, Neisseria meningitidis, Group B Streptococcus, Listeria monocytogenes, and Haemophilus influenzae. Other pathogens include viruses (e.g., herpesviruses, HIV), spirochetes such as Treponema pallidum, and Borrelia burgdorferi.
Clinically, patients often present with fever, headache, vomiting, and altered mental status. Classical meningeal signs include nuchal rigidity, Kernig’s sign, and Brudzinski’s sign, although these may not always be present. A petechial or purpuric rash suggests meningococcal infection. Severe cases may progress to seizures, coma, or focal neurologic deficits.
Presentation may be atypical in elderly patients and neonates.
Diagnosis requires urgent evaluation. Initial laboratory tests include blood work and cultures, followed by lumbar puncture to analyze CSF. In bacterial meningitis, CSF typically shows high white blood cell count with neutrophil predominance, low glucose, and elevated protein. In viral meningitis, lymphocytes predominate, and glucose is usually normal. PCR testing improves detection of both bacterial and viral pathogens. A CT scan of the head is indicated before lumbar puncture in patients with risk factors for increased intracranial pressure or focal neurologic signs.
Treatment must be initiated immediately, often before confirmation of the causative organism. Empiric therapy typically includes a third- or fourth-generation cephalosporin combined with vancomycin, with the addition of ampicillin when Listeria is suspected. Therapy is later tailored based on culture results. Adjunctive corticosteroids may be beneficial in certain cases, particularly pneumococcal meningitis, to reduce inflammation and neurologic complications.
All patients require hospitalization for close monitoring and supportive care. Prognosis depends on factors such as age, underlying health, pathogen, and timeliness of treatment. Mortality and morbidity increase with delayed therapy, altered consciousness, or severe disease at presentation.
Complications can be severe and include seizures, hydrocephalus, brain abscess, hearing loss, cognitive impairment, paralysis, and even death. Survivors often require long-term neurologic follow-up and rehabilitation.
Acute meningitis is a rapidly developing inflammation of the meninges that typically evolves over hours to days. It may resolve spontaneously in viral cases or require urgent treatment when bacterial in origin. Despite advances in therapy, it remains a medical emergency due to its potential for rapid deterioration and severe complications.
Meningitis occurs worldwide and can affect individuals of all ages, including previously healthy people. The overall incidence in the United States is approximately 2–10 cases per 100,000 population annually, with significantly higher rates in neonates and young children. Among bacterial causes, Neisseria meningitidis is unique in its ability to cause epidemics. Vaccination programs have significantly reduced cases of Haemophilus influenzae type B meningitis.
Risk factors include extremes of age, crowded living conditions, close contact with infected individuals, head trauma, neurosurgical devices (e.g., shunts), immunosuppression, and chronic illnesses. Specific conditions predispose to certain pathogens—for example, asplenia increases risk for pneumococcal and meningococcal infections, while complement deficiencies increase susceptibility to meningococcal disease. Tick exposure may lead to Lyme meningitis.
The pathogenesis begins with colonization of the nasopharynx, followed by invasion into the bloodstream and crossing of the blood–brain barrier into the cerebrospinal fluid (CSF), where pathogens multiply. Inflammation in the subarachnoid space leads to increased intracranial pressure and neurologic dysfunction.
Etiologically, most cases are viral, particularly due to enteroviruses. However, bacterial meningitis is more severe and commonly caused by Streptococcus pneumoniae, Neisseria meningitidis, Group B Streptococcus, Listeria monocytogenes, and Haemophilus influenzae. Other pathogens include viruses (e.g., herpesviruses, HIV), spirochetes such as Treponema pallidum, and Borrelia burgdorferi.
Clinically, patients often present with fever, headache, vomiting, and altered mental status. Classical meningeal signs include nuchal rigidity, Kernig’s sign, and Brudzinski’s sign, although these may not always be present. A petechial or purpuric rash suggests meningococcal infection. Severe cases may progress to seizures, coma, or focal neurologic deficits.
Presentation may be atypical in elderly patients and neonates.
Diagnosis requires urgent evaluation. Initial laboratory tests include blood work and cultures, followed by lumbar puncture to analyze CSF. In bacterial meningitis, CSF typically shows high white blood cell count with neutrophil predominance, low glucose, and elevated protein. In viral meningitis, lymphocytes predominate, and glucose is usually normal. PCR testing improves detection of both bacterial and viral pathogens. A CT scan of the head is indicated before lumbar puncture in patients with risk factors for increased intracranial pressure or focal neurologic signs.
Treatment must be initiated immediately, often before confirmation of the causative organism. Empiric therapy typically includes a third- or fourth-generation cephalosporin combined with vancomycin, with the addition of ampicillin when Listeria is suspected. Therapy is later tailored based on culture results. Adjunctive corticosteroids may be beneficial in certain cases, particularly pneumococcal meningitis, to reduce inflammation and neurologic complications.
All patients require hospitalization for close monitoring and supportive care. Prognosis depends on factors such as age, underlying health, pathogen, and timeliness of treatment. Mortality and morbidity increase with delayed therapy, altered consciousness, or severe disease at presentation.
Complications can be severe and include seizures, hydrocephalus, brain abscess, hearing loss, cognitive impairment, paralysis, and even death. Survivors often require long-term neurologic follow-up and rehabilitation.
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Infectious Disease and Microbiology - Mediastinitis
Mediastinitis is a serious infection involving the mediastinum, the central compartment of the thoracic cavity. It may present as acute or chronic disease. Acute mediastinitis is a life-threatening condition often resulting from esophageal perforation, cardiothoracic surgery, trauma, or spread from nearby infections such as those of the head and neck. A particularly severe form is descending necrotizing mediastinitis, where infection spreads rapidly from the oropharynx into the chest. Chronic mediastinitis is less common and is typically associated with granulomatous diseases such as tuberculosis or histoplasmosis, or with retained foreign bodies.
Currently, most cases of mediastinitis occur as complications following cardiac surgery, especially after sternotomy. The incidence of post-surgical mediastinitis ranges from approximately 0.4% to 5%. Despite advances in surgical techniques and infection control, the incidence has remained stable due to increasing numbers of elderly and immunocompromised patients undergoing complex procedures. Risk factors include diabetes mellitus, obesity, chronic lung disease, prolonged surgical time, reoperation, and vascular comorbidities.
The pathophysiology involves invasion of the mediastinum by pathogens, leading to intense inflammation, fibrin deposition, and formation of abscesses. Infection can spread rapidly through fascial planes, creating extensive tissue damage and dead space beneath the sternum. Acute infections are usually polymicrobial. Common organisms include gram-positive bacteria such as Staphylococcus aureus and Staphylococcus epidermidis in post-surgical cases, while infections related to esophageal or oropharyngeal sources often involve gram-negative and anaerobic organisms. In severely ill patients, fungal pathogens like Candida and Aspergillus may also be involved.
Clinically, acute mediastinitis presents with fever, severe chest pain, dysphagia, and respiratory distress. Patients with esophageal perforation may also have epigastric pain. Physical findings can include a sternal click (indicating instability), crepitus due to subcutaneous air, and Hamman’s sign, a crunching sound heard over the chest. In contrast, chronic mediastinitis may initially be asymptomatic but later presents with symptoms due to compression of mediastinal structures, such as cough, dyspnea, or signs of superior vena cava syndrome.
Laboratory findings typically show leukocytosis and elevated inflammatory markers such as C-reactive protein. Blood cultures may be positive, especially in cases associated with head and neck infections. Imaging is essential for diagnosis. Chest radiographs may reveal mediastinal widening or air-fluid levels, while CT scans provide detailed visualization of fluid collections, gas, and the extent of infection. Diagnostic procedures such as CT-guided aspiration, mediastinoscopy, or thoracoscopy may be required to obtain microbiological samples.
Management of mediastinitis requires urgent and aggressive treatment. Broad-spectrum intravenous antibiotics should be initiated promptly and later tailored based on culture results. Common regimens include combinations of cephalosporins with anaerobic coverage or agents such as piperacillin-tazobactam. Coverage for MRSA may require vancomycin or linezolid. Therapy is typically prolonged, lasting several weeks.
Surgical intervention is critical and remains the cornerstone of treatment. Procedures include drainage of infected material, debridement of necrotic tissue, and sometimes more extensive approaches such as thoracotomy or video-assisted thoracic surgery. Negative pressure wound therapy may be used in postoperative cases. Supportive care, including airway management, oxygen therapy, and adequate nutrition, is essential.
The prognosis of mediastinitis is guarded, with mortality rates reaching up to 50%, especially in delayed or inadequately treated cases. Early diagnosis and prompt surgical drainage significantly improve outcomes. Complications can be severe and include sepsis, pleural empyema, sternal osteomyelitis, acute respiratory distress syndrome, thrombosis, and superior vena cava syndrome.
Mediastinitis is a serious infection involving the mediastinum, the central compartment of the thoracic cavity. It may present as acute or chronic disease. Acute mediastinitis is a life-threatening condition often resulting from esophageal perforation, cardiothoracic surgery, trauma, or spread from nearby infections such as those of the head and neck. A particularly severe form is descending necrotizing mediastinitis, where infection spreads rapidly from the oropharynx into the chest. Chronic mediastinitis is less common and is typically associated with granulomatous diseases such as tuberculosis or histoplasmosis, or with retained foreign bodies.
Currently, most cases of mediastinitis occur as complications following cardiac surgery, especially after sternotomy. The incidence of post-surgical mediastinitis ranges from approximately 0.4% to 5%. Despite advances in surgical techniques and infection control, the incidence has remained stable due to increasing numbers of elderly and immunocompromised patients undergoing complex procedures. Risk factors include diabetes mellitus, obesity, chronic lung disease, prolonged surgical time, reoperation, and vascular comorbidities.
The pathophysiology involves invasion of the mediastinum by pathogens, leading to intense inflammation, fibrin deposition, and formation of abscesses. Infection can spread rapidly through fascial planes, creating extensive tissue damage and dead space beneath the sternum. Acute infections are usually polymicrobial. Common organisms include gram-positive bacteria such as Staphylococcus aureus and Staphylococcus epidermidis in post-surgical cases, while infections related to esophageal or oropharyngeal sources often involve gram-negative and anaerobic organisms. In severely ill patients, fungal pathogens like Candida and Aspergillus may also be involved.
Clinically, acute mediastinitis presents with fever, severe chest pain, dysphagia, and respiratory distress. Patients with esophageal perforation may also have epigastric pain. Physical findings can include a sternal click (indicating instability), crepitus due to subcutaneous air, and Hamman’s sign, a crunching sound heard over the chest. In contrast, chronic mediastinitis may initially be asymptomatic but later presents with symptoms due to compression of mediastinal structures, such as cough, dyspnea, or signs of superior vena cava syndrome.
Laboratory findings typically show leukocytosis and elevated inflammatory markers such as C-reactive protein. Blood cultures may be positive, especially in cases associated with head and neck infections. Imaging is essential for diagnosis. Chest radiographs may reveal mediastinal widening or air-fluid levels, while CT scans provide detailed visualization of fluid collections, gas, and the extent of infection. Diagnostic procedures such as CT-guided aspiration, mediastinoscopy, or thoracoscopy may be required to obtain microbiological samples.
Management of mediastinitis requires urgent and aggressive treatment. Broad-spectrum intravenous antibiotics should be initiated promptly and later tailored based on culture results. Common regimens include combinations of cephalosporins with anaerobic coverage or agents such as piperacillin-tazobactam. Coverage for MRSA may require vancomycin or linezolid. Therapy is typically prolonged, lasting several weeks.
Surgical intervention is critical and remains the cornerstone of treatment. Procedures include drainage of infected material, debridement of necrotic tissue, and sometimes more extensive approaches such as thoracotomy or video-assisted thoracic surgery. Negative pressure wound therapy may be used in postoperative cases. Supportive care, including airway management, oxygen therapy, and adequate nutrition, is essential.
The prognosis of mediastinitis is guarded, with mortality rates reaching up to 50%, especially in delayed or inadequately treated cases. Early diagnosis and prompt surgical drainage significantly improve outcomes. Complications can be severe and include sepsis, pleural empyema, sternal osteomyelitis, acute respiratory distress syndrome, thrombosis, and superior vena cava syndrome.
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Infectious Disease and Microbiology - Measles
Measles is a highly contagious viral disease characterized by fever and a distinctive maculopapular rash that begins on the face and spreads downward to the trunk and extremities. The rash is typically preceded by a prodromal phase of cough, coryza, and conjunctivitis, along with the pathognomonic Koplik’s spots on the buccal mucosa. While often self-limited in healthy children, measles remains a major cause of morbidity and mortality, particularly in malnourished or immunocompromised populations.
Globally, measles continues to affect millions of individuals each year, with significant mortality despite widespread vaccination efforts. Although vaccination coverage has improved, outbreaks still occur, especially in low-income countries and in areas affected by conflict or poor healthcare access. Individuals at highest risk include those who are unvaccinated, immunocompromised, pregnant, malnourished, or at extremes of age. Healthcare workers without immunity are also at risk and may contribute to transmission.
The virus spreads via respiratory droplets and initially infects the respiratory mucosa before disseminating through lymphatic and hematogenous routes. It affects multiple organ systems including the skin, conjunctiva, lungs, and gastrointestinal tract. The appearance of the rash corresponds with the host immune response and marks the decline in viral transmissibility. The causative agent is the measles (rubeola) virus, an RNA virus of the Paramyxoviridae family.
Clinically, measles begins with a prodrome of high fever, cough, conjunctivitis, and coryza. Koplik’s spots—small white lesions on the buccal mucosa—appear early and are highly characteristic. This is followed by a red maculopapular rash that starts behind the ears and on the forehead, then spreads downward. The rash typically lasts about five days before fading, sometimes followed by desquamation. In partially immune individuals, atypical and milder presentations may occur.
Diagnosis is primarily clinical, based on characteristic signs and symptoms. Laboratory findings may include leukopenia, T-cell cytopenia, and thrombocytopenia. Serologic testing can confirm diagnosis in atypical cases. Chest imaging may reveal interstitial pneumonitis in severe disease. Viral detection can be performed using immunofluorescence or PCR from respiratory secretions or urine, though this is not always necessary in typical cases.
There is no specific antiviral therapy for measles. Management is mainly supportive, focusing on hydration, fever control, and monitoring for complications. The World Health Organization recommends vitamin A supplementation in children, particularly in developing countries, as it reduces morbidity and mortality. Ribavirin may be considered in severe cases among immunocompromised patients. Antibiotics are reserved only for secondary bacterial infections. Post-exposure prophylaxis with immune serum globulin may prevent or attenuate disease in high-risk individuals.
Prevention is primarily achieved through vaccination with the measles-containing vaccine (commonly the MMR vaccine). The standard schedule includes an initial dose at 12–15 months and a booster at 4–6 years. Vaccination has dramatically reduced global incidence, and there is no evidence linking the vaccine to autism. Certain groups, such as pregnant women and severely immunocompromised individuals, should not receive the live vaccine.
The prognosis is generally excellent in healthy individuals, with lifelong immunity following recovery. However, complications are common in vulnerable populations and may include pneumonia, encephalitis, otitis media, severe diarrhea, and blindness. A rare but fatal long-term complication is subacute sclerosing panencephalitis (SSPE), which can occur years after the initial infection.
Measles is a highly contagious viral disease characterized by fever and a distinctive maculopapular rash that begins on the face and spreads downward to the trunk and extremities. The rash is typically preceded by a prodromal phase of cough, coryza, and conjunctivitis, along with the pathognomonic Koplik’s spots on the buccal mucosa. While often self-limited in healthy children, measles remains a major cause of morbidity and mortality, particularly in malnourished or immunocompromised populations.
Globally, measles continues to affect millions of individuals each year, with significant mortality despite widespread vaccination efforts. Although vaccination coverage has improved, outbreaks still occur, especially in low-income countries and in areas affected by conflict or poor healthcare access. Individuals at highest risk include those who are unvaccinated, immunocompromised, pregnant, malnourished, or at extremes of age. Healthcare workers without immunity are also at risk and may contribute to transmission.
The virus spreads via respiratory droplets and initially infects the respiratory mucosa before disseminating through lymphatic and hematogenous routes. It affects multiple organ systems including the skin, conjunctiva, lungs, and gastrointestinal tract. The appearance of the rash corresponds with the host immune response and marks the decline in viral transmissibility. The causative agent is the measles (rubeola) virus, an RNA virus of the Paramyxoviridae family.
Clinically, measles begins with a prodrome of high fever, cough, conjunctivitis, and coryza. Koplik’s spots—small white lesions on the buccal mucosa—appear early and are highly characteristic. This is followed by a red maculopapular rash that starts behind the ears and on the forehead, then spreads downward. The rash typically lasts about five days before fading, sometimes followed by desquamation. In partially immune individuals, atypical and milder presentations may occur.
Diagnosis is primarily clinical, based on characteristic signs and symptoms. Laboratory findings may include leukopenia, T-cell cytopenia, and thrombocytopenia. Serologic testing can confirm diagnosis in atypical cases. Chest imaging may reveal interstitial pneumonitis in severe disease. Viral detection can be performed using immunofluorescence or PCR from respiratory secretions or urine, though this is not always necessary in typical cases.
There is no specific antiviral therapy for measles. Management is mainly supportive, focusing on hydration, fever control, and monitoring for complications. The World Health Organization recommends vitamin A supplementation in children, particularly in developing countries, as it reduces morbidity and mortality. Ribavirin may be considered in severe cases among immunocompromised patients. Antibiotics are reserved only for secondary bacterial infections. Post-exposure prophylaxis with immune serum globulin may prevent or attenuate disease in high-risk individuals.
Prevention is primarily achieved through vaccination with the measles-containing vaccine (commonly the MMR vaccine). The standard schedule includes an initial dose at 12–15 months and a booster at 4–6 years. Vaccination has dramatically reduced global incidence, and there is no evidence linking the vaccine to autism. Certain groups, such as pregnant women and severely immunocompromised individuals, should not receive the live vaccine.
The prognosis is generally excellent in healthy individuals, with lifelong immunity following recovery. However, complications are common in vulnerable populations and may include pneumonia, encephalitis, otitis media, severe diarrhea, and blindness. A rare but fatal long-term complication is subacute sclerosing panencephalitis (SSPE), which can occur years after the initial infection.
