robin082006
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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.  Antibiotics to inhibit normal flora
B. .gif) Cold temperature
C. Egg yolk cholesterol
D. Reduced oxygen tension
E. Staphylococcus aureus
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| msyamp
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thayer martin media ans A. contains colistin nystation vancomycin
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| sturge_weber
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why thayer martin media, it says gram negative bacilli, not gram negative cocci
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| sturge_weber
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i think if gram negative bacilli, then must be haemophilus, requires factor v and x and also grows near staph aureus, hence e
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| msyamp
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oh ya sturge. see i am not reading the question fully. a very wrong thing to do.
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| robin082006
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yes, ans is E
it is called satellite phenomenon.
HI needs NAD and hematin to grow. S. Aureus is needed to create hematin for the culture.
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| msyamp
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yes thanq
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| bactitech
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E is correct. However, eye cultures are ALWAYS planted on chocolate agar. Hemophilus influenzae grows quite well on chocolate. We plant eyes on blood, chocolate, MacConkey and CNA (blood with colistin/Nalidixic acid that inhibits gram negatives). We hold plates on eyes four days before signing them out.
Hemophilus is usually ID'd by using X and V factor discs or strips (they come both ways commercially). We sub the bug to blood and chocolate for more growth. If NG on BAP, and the gram is tiny gram negative rods, we set up the XV. The organism is subbed to TSA (trypticase soy agar without blood) or BHI (brain heart infusion without blood) in a confluent growth. The X and V strips are placed parallel to each other about 10 mm apart. HI will grow between the strips, as it needs both X and V. H. parainfluenzae will only grow around the V strip.
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