Legionnaires' Disease #9

Medical Microbiology Disease of the week 4

classification

Legionnaires’ Disease (Legionellosis)

causative organism

Legionella pneumophila

(gram-negative rod, intracellular parasite, biofilms)

epidemiology

reservoir- environment (water + soil)

portal of entry- respiratory tract

transmission- inhalation of contaminated water aerosols or aspiration of contaminated water

incubation

4hrs-10 days (depending on disease)

pathogenesis

bacteria multiply in alveolar macrophages resulting in cell death and spread of infection. tissue necrosis and inflammation result in multiple small abscesses, pneumonia, and pleurisy

virulence

protein needle secretes proteins into macrophage housing that does not allow for its destruction

sypmtoms

pontiac fever: fever, muscular aches, fatigue, headache, cough, difficultly breathing, resolves spontaneously

pneumonia: 2-10 day incubation, Pontiac fever symptoms, shortness of breath, sputum, chest pain, confusion, diarrhea, abdominal pain, vomiting

complications

chronic fatigue, pulmonary fibrosis, confections or superinfections, infections of other organ systems, respiratory failure (mortality) 15% of hospitalized

treatment

antibiotics: macrolides (erythromycin, azithromycin), tetracycline, quinolones (broad spectrum; levofloxacin)

prevention

environmental design and maintenance, avoid smoking and alcohol abuse