Flashcards in History and Legionella Deck (7)
What is Koch's Postulate?
1. The organism is found in the diseased
2. The organism can be isolated in pure culture.
3. Inoculation of animals with organisms from the pure culture produces a similar disease.
4. The organism can be recovered from the lesions of these animals.
How is Legionella pneumophila transmitted?
They grow in amoebae in the water. When misted (aerosols) they reach the lungs and cause pneumonia. Legionella are thermophiles, and there is no person-to-person transmission.
What are the risk factors of legionella?
older than 50, immunosuppressed, diabetes, cancer, COPD, smoker
What is Pontiac Fever?
Caused by the serogroups 1-6 of L. pneumophila. Only recognized in outbreaks. It is a self-limiting, flu-like illness with NO PNEUMONIA and is not fatal.
How can you diagnose L. pneumophila?
1. Isolation on buffered charcoal yeast extract agar
2. Detection of Legionella antigens in urine for serogroup 1 ONLY.
3. Visualization of organisms in smears by fluorescent antibody
4. Retrospectively, by a 4-fold rise in indirect fluorescent antibody titer against the organism, comparing acute versus convalescent serum samples. (retrospective)
5. Molecular probes
How do you treat L. pneumophila?
1. Erythromycin (able to penetrate into mammalian cells, and L pnemophila lives in macrophages)
2. DO NOT use ampicillin (not able to penetrate the cells)