Deck 34: Legionella

Question 1

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.

Answer 1

D
All members of the genus Legionella are faintly staining, thin, gram-negative bacilli

Question 2

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 2

B
Legionella is the causative agent of legionnaires' disease, a febrile and pneumonic illness with numerous clinical presentations. Legionella was discovered 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. There is retrospective serologic evidence of Legionella infection as far back as 1947.

Question 3

Specimens for culture recovery of Legionella should be inoculated to

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

Answer 3

A
Specimens for culture should be inoculated to two agar plates for 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 ACES buffer and the growth supplements cysteine (required by Legionella), yeast extract, α-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 4

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

A)L-cysteine
B)Blood and cysteine
C)Dopa-cysteine
D)Nicotinic adenine
E)All of the above are correct.