Gram Negative Coccobacilli
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. 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.