​Kembara Xtra - Medicine - Legionnaires' Disease

​Kembara Xtra - Medicine - Legionnaires' Disease 
Legionnaires' disease was called after an outbreak of a lower respiratory tract infection at the American Legion conference in Philadelphia in 1976. Legionella pneumophila, a previously unidentified causal bacterium, was isolated, characterized, and named. The infection mainly causes pneumonia and flu-like symptoms. Commercial water systems, such as those in hotels, hospitals, apartment complexes, and air conditioning cooling towers, are more frequently colonized by Legionella. It is the most prevalent atypical pneumonia and one of the top three causes of pneumonia.
System(s) impacted include the GI and respiratory systems.
 Synonym(s): Pontiac fever (self-limited influenza-like illness without pneumonia caused by Legionella species); legionellosis; Legionella pneumonia

Epidemiology 

 Patients range in age from 15 months to 84 years; 74–91% are over 50.
 Males predominate over females
Incidence
Nearly 10,000 cases of Legionnaires' disease were reported in the United States in 2018, a 4-fold rise since 2000. Outbreaks are most frequent in the late summer and early fall, accounting for 2-9% of all pneumonia cases in the country.
One out of every ten instances of the legionnaires' disease is deadly.


Pathophysiology and Etiology 

A weak gram-negative aerobic saprophytic freshwater bacteria, L. pneumophila. It is widely dispersed in both water and soil. It exists in nature as a protozoan parasite and is frequently found in freshwater biofilms. Bipolar flagella give movement; it grows best at 40–45°C.
Clinical illness is caused by serogroups 1 to 6, with serogroup 1 accounting for between 70 and 92 percent of all clinical cases of Legionella in the US.
Alveolar macrophages in the lung become infected by Legionella.
The organism can be spread by inhaling infected water droplets or by aspirating contaminated water (for example, the first Philadelphia outbreak was brought on by contaminated shower water).
Whirlpools, spas, fountains, and cruise ships have all been linked to community outbreaks.

Legionella are intracellular infections, therefore one risk factor is impaired cellular immunity.
a chronic cardiac condition, advanced age, usage of antibiotics during the previous three months, immunosuppression, HIV, diabetes, organ transplant recipients, and male gender.

Prevention 
Not contagious (respiratory isolation is not essential.)
Water systems should be superheated and flushed after heating the water to at least 70°C.
Both copper-silver ionization and ultraviolet light are bactericidal.
The danger of Legionella infection is reduced when municipal water supplies are disinfected with monochloramine.
 0.2 micron water filters—regular replacement is required
 Keep hot water heaters at 60 degrees and cold water at 20 degrees.

Diagnoses include everything from mild febrile sickness and silent seroconversion to life-threatening pneumonia.
Additionally, Legionella wound infections have been recorded. The incubation period is 2 to 14 days.


History 

 Symptoms (with corresponding percentage):
- Cough: 92% (usually dry and ineffective)
- Fever and chills: 90%
Dyspnea: 62%
- Chest discomfort with pleurisy: 35%
- Migraine: 48%
- Arthralgia/myalgia: 40%
- Diarrhea with water: 50%
- Vomiting and diarrhoea: 49%
Encephalopathy, confusion, disorientation, obtundation, depression, hallucinations, sleeplessness, and seizure are among the neuropsychiatric symptoms that account for 53% of cases.
Immunosuppression history raises risk.

clinical assessment 

Fever: Relative bradycardia (key sign) 102°F or lower temperature with an abnormally low pulse rate of 100 beats per minute (normal compensatory response to fever is >110 beats per minute).
Rales and indications of consolidation (such as pectoral egophony, tactile fremitus, or pectoriloquy)
DISTINCTIVE DIAGNOSIS
 Additional bacterial pneumonias, particularly unusual pneumonias Chlamydophila psittaci, Francisella tularensis, Chlamydophila pneumoniae, Q fever (Coxiella burnetii), and Mycoplasma pneumoniae
Viral pneumonias such adenovirus, influenza (human, avian, and swine), and cytomegalovirus (CMV) need to be distinguished from COVID-19 pulmonary illness; COVID-19 testing is advised.


Laboratory Results 

Indications for Legionella testing include: CAP that has not responded to outpatient antibiotic therapy; severe pneumonia, especially that entails intensive care; and pneumonia in individuals with weakened immune systems.
Patients with a history of leaving their home within 10 days of the onset of their illness, particularly those who have stayed in hotels or on cruise ships within the previous two weeks, Pneumonia in the presence of a known outbreak of Legionnaires' disease, and Pneumonia starting 48 hours after hospital admission
Initial examinations (lab, imaging)
Urinary antigen test (UAT) detects serogroup 1 (which causes 80% of sickness), while Legionella PCR detects 100% of all Legionella species from lower respiratory secretions. UATs have a wide range of sensitivity yet are quite specific (95- 100%).
A sufficient sputum sample and specialized media (buffered charcoal yeast extract [BCYE] agar) are needed for legionella cultivation (gold standard). The sensitivity of culture varies (10-80%), and findings can take up to 7 days to appear.
● Other aberrant lab results:
- Hyponatremia - Temporary hypophosphatemia
Lymphopenia, moderately elevated serum transaminases, increased LDH, and increased creatine kinase
- Miniscule hematuria - Extremely high C-reactive protein (CRP) levels (>30)
- Extremely high ferritin levels (2 times normal)
Chest radiograph: Not specific for Legionella; frequently reveals consolidation of a unilateral lower lobe patchy alveolar infiltrate; immunocompromised patients are more likely to develop cavitation and abscesses. Up to 50% of patients experience pleural effusion. The resolution of radiographic abnormalities could take 1 to 4 months. Despite receiving antibiotics, the infiltrate can be observed to be progressing on an x-ray.

Other/Diagnostic Procedures
To acquire sputum or lung samples, transtracheal aspiration or bronchoscopy may occasionally be necessary.
Interpretation of Tests
 Serous or serosanguineous pleural effusion may accompany multi-focal pneumonia with alveolitis, bronchiolitis, and fibrinous pleuritis.
Up to 20% of patients develop abscesses.
Even with the proper treatment, the progression of infiltrates on an x-ray suggests Legionnaires' illness. There may be significant lag times between radiographic and clinical results as they improve.
Procalcitonin levels have limited utility since atypical infections like Legionella do not respond as well to them.

Management - Supportive care: - Electrolyte balance, oxygenation, and hydration along with antibiotic treatment
AIDS patients may experience extrapulmonary problems and increased mortality.
 If a patient has a severe case of pneumonia, obtain UAT and begin empiric antibiotics that cover Legionella.


First Line of Medicine
No prospective randomized controlled trials have compared fluoroquinolones to macrolides for the treatment of Legionella; levofloxacin is associated with more rapid defervescence, fewer complications, decreased hospital stay by 3 days, and decreased mortality (4% vs. 10.9%) when compared to macrolide antibiotics. Antibiotics that achieve high intracellular concentrations (e.g., macrolides, tetracyclines, fluoroquinolones) If you are sufficiently unwell from the GI symptoms brought on by Legionella, start parenteral antibiotics:
- Levofloxacin is the recommended medication:
 Levofloxacin 750 mg/day IV for 5 days or 750 mg/day for 7 to 10 days (transition to oral when patient is afebrile and tolerating oral).
- First-line treatment may also use azithromycin. Due to a greater half-life than levofloxacin, the course of treatment is shorter:
Azithromycin 500 mg/day IV (switch to oral form when afebrile or tolerating oral form) for 7 to 10 days - Contraindications: hypersensitivity reactions - Precautions: liver disease - Significant drug interactions: - Can increase theophylline, carbamazepine, and digoxin levels - Can increase activity of oral anticoagulants - May decrease the effectiveness of digoxin, quinidine, oral contraceptives, and

Next Line
Doxycycline should not be used by pregnant women, and it is not permitted for use in children under the age of eight. Doxycycline 100 mg IV/PO q12h for 14 days; for severe infections, the initial dose is 200 mg IV/PO q12h.


Admission, intolerance to oral antibiotics, hypoxia, and requirements for immediate admission to the intensive care unit
- Any important requirements for severe CAP:
Acute respiratory failure requiring intubation and/or mechanical ventilation and necessitating vasopressor support
- Three or more minor requirements for CAP severity:
 Hypothermia (temperature 36°C), hypotension necessitating extensive fluid resuscitation, RR 30 breaths per minute, PaO2:FiO2 ratio 250, multilobular infiltrates, confusion/disorientation, uremia (BUN 20 mg/dL), leukopenia (WBC 4,000 cells/mm3), thrombocytopenia (PLT 100,000 cells/mm3)
Afebrile and able to tolerate oral antibiotics are the discharge requirements.
- Regain baseline/normal room-air oxygen saturation

Patient Follow-Up Monitoring
 Pay particular attention to the electrolyte, hydration, and respiratory statuses.
Chest radiography is not always accurate and may not be useful for tracking a clinical response.


Modification of Lifestyle 

 Eliminate pathogens from water sources, clean cooling towers with minimal emissions while taking control measurements of water and air samples.
Legionella does not transfer from one person to another.

Prognosis: When the right antibiotics are begun early in the course of the illness, the prognosis is improved. Recovery is variable: Patients may experience clinical deterioration despite receiving the right first treatment (first 1–2 days of therapy).
- It is common to have improvement with defervescence in 3 to 5 days and full recovery in 6 to 10 days. Some have a longer trajectory.
 Nosocomial infections can cause up to 34% of deaths.

Complications 

 Bacteremia/lung abscess formation in up to 20% of patients Hyponatremia Respiratory insufficiency necessitating ventilator assistance Extrapulmonary diseases:
- Encephalitis, cellulitis, sinusitis, pancreatitis, pyelonephritis, pericarditis, and perirectal abscess (endocarditis is the most common extrapulmonary location).
 Renal dysfunction
Death occurs in 8–12% of treated immunocompetent patients and up to 80% of untreated immunocompromised patients due to disseminated intravascular coagulation, multiple organ dysfunction syndrome (MODS), and coma.

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