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Microbiology

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Gram Negative Coccobacilli

Question
56 out of 58
 

A 55-year-old man who is being treated for adenocarcinoma of the lung is admitted to a hospital because of fever , chest pain, and cough. Gram stain of the sputum is unremarkable, and culture reveals many small, gram-negative rods able to grow only on a charcoal yeast extract agar. Most likely organism is?



A Chlamydia trachomatis
B Klebsiella pneumoniae

C Legionella pneumophila
D M. pneumonia

Ans. C Legionella pneumophila

a. The symptoms of Legionnaires' dis­ease are similar to those of mycoplasmal pneumonia and influenza. Affected persons are moderately febrile, complain of pleuritic chest pain, and have a dry cough.

b. Unlike Klebsiella and Staphylococcus, L. pneumophila exhibits fas­tidious growth requirements. Charcoal yeast extract agar either with or without antibiotics is the preferred isolation medium.

c. While sputum may not be the specimen of choice for Legionella, the discovery of small, gram­ negative rods by direct fluorescent antibody (FA) technique should certainly heighten suspicion of the disease. L. pneumophila is a facultative intracellular pathogen and enters macrophages without activating their oxidizing capa­bilities.

d. The organisms bind to macrophage C receptors, which promote engulfment.

Gram Negative Coccobacilli Flashcard List

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