Deck 34: Legionella

Question 1

A febrile and pneumonic illness first named in 1976 by scientists at the Centers for Disease Control and Prevention (CDC)who were investigating an epidemic of pneumonia among Pennsylvania State American Legion members attending a convention in Philadelphia is known as:

A) Philadelphia pneumonia.
B) legionnaires' disease.
C) tuberculosis.
D) rheumatic fever.

Answer 1

B
Legionella is the causative agent of Legionnaires' disease, a febrile and pneumonic illness with numerous clinical presentations.Scientists at the CDC, who were investigating an epidemic of pneumonia among Pennsylvania State American Legion members attending a convention in Philadelphia, discovered Legionella in 1976.Retrospective serologic evidence of Legionella infection has, however, been recognized as far back as 1947.

Question 2

The medium or media of choice used to recover Legionella is:

A) buffered charcoal yeast extract (BCYE).
B) Regan-Lowe agar.
C) Löwenstein-Jensen medium.
D) blood and chocolate agars.

Answer 2

A
Specimens for culture should be inoculated to two agar plates for the recovery of Legionella, at least one of which is BCYE without inhibitory agents.This medium contains charcoal to detoxify the medium, remove carbon dioxide (CO₂), and modify the surface tension to allow the organisms to proliferate more easily.BCYE is also prepared with N-(2-Acetamido)-2-aminoethanesulfonic acid (ACES)buffer and the growth supplements cysteine (required by Legionella), yeast extract, alpha-ketoglutarate, and iron.A second medium, BCYE base with polymyxin B, anisomycin (to inhibit fungi), and cefamandole, is recommended for specimens such as sputum that are likely to be contaminated with other flora.

Question 3

To cultivate Legionella in the laboratory, a medium supplemented with what ingredient(s)is necessary?

A) L-cysteine and iron
B) Blood and cysteine
C) Dopa-cysteine
D) Nicotinic adenine

Answer 3

A
Only one genus, Legionella, exists in the Legionellaceae family.All members of this genus are faintly staining, thin, gram-negative bacilli that require a medium supplemented with iron and L-cysteine and buffered to pH 6.9 for optimal growth.

Question 4

A direct immunofluorescent antibody (DFA)test was performed on a sputum sample that yielded a positive test.The organism grew on BCYE medium and was a thin gram-negative, faintly staining bacillus.What is the drug of choice for this organism?

A) Fluoroquinolones
B) Erythromycin
C) Penicillin
D) Aminoglycosides

Question 5

Organisms belonging to the genus Legionella are:

A) gram-positive diplococci.
B) gram-positive diphtheroid bacilli.
C) gram-negative coccobacilli.
D) faintly staining, thin gram-negative bacilli.