Properties

Pathogenesis

Clinical findings

Laboratory diagnosis

Treatment & Prevention

Gram-negative rods.

Stain faintly with Gram stain

Environmental bacteria which grow in:

- air conditioners

- water-cooling towers

Outbreak of pneumonia in hospitals due to presence of organisms in water taps, sinks, and showers.

Portal of entry is respiratory tract, & pathologic changes occur primarily in the lung.

Predisposing factors:

- old age

- male

- smoker / alcoholic

- patients with AIDS, cancer, transplants.

Air-borne transmission, person-to-person spread does not occur.

Disease:

- pontiac fever

- Legionnaires’ disease

Pontiac fever: mild influenzalike illness.

Legionnaires’ disease:

- severe pneumonia.

- mental confusion

- nonbloody diarrhea

- proteinuria

- microscopic hematuria

Immunofluorescent stain.

Cultured on a special medium, B-CYE agar.

Detection of antigens in the urine.

Erythromycin; add rifampicin if patient fails to respond.

Beta-lactamase production render penicillins & cephalosporins less effective.

Prevention:

- reducing cigarette & alcohol consumption.

- eliminating aerosols from water sources.

- reducing incidence of Legionella in hospital water supplies by using high temperatures & hyperchlorination.