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Microbiology

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Gram Negative Coccobacilli

Question
34 out of 58
 

A 16-year-old girl presents to her physician complaining of redness and a yellowish discharge from her left eye for the past 2 days. She reports minimal crusting upon awakening and denies eye pain or previous traumA. Upon examination, there is diffuse conjunctival hyperemia associated with a mucoid discharge. The pupils dilate normally, although there is mild photophobia in the affected eye. Gram's stain of the exudate shows pleomorphic, gram-negative bacilli. To culture this organism with whole blood agar, which of the following must be used?



A Cold temperature

B Egg yolk cholesterol

C Reduced oxygen tension

D Staphylococcus aureus

Ans. D Staphylococcus aureus

a. The most common cause of bacterial conjunctivitis is H. influenza. The observation of pleomorphic gram negative bacilli confirms hemophilus as the cause.

b. Hemophilus influenzae grows on blood agar but growth is scanty as the V factor is not freely available, being trapped inside the red blood cells.

c. To grow it on blood agar on which a specimen containing H. influenzae has been inoculated, a S.aureus streak will cause beta hemolysis and relase V factor. After overnight incubation, the colonies of H. influenae will be large and well developed alongside the streak of Staphylococcus, and smaller farther away. This phenomenon is called SATELLITISM

Gram Negative Coccobacilli Flashcard List

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