jean robert
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35 y.o. women presents to her gynecologist with complaints of burning on urination for the past 2 days. Dipstick test of her urine demonstrates marked positivity for leukocyte esterase, but no reactivity for nitrite. Urine culture later grows out large numbers of organisms. Which of the following bacteria are most likely to be responsible for this patient s infection?
a) Enterobacter sp.
b) Enterococcus faecalis
c) E.coli
d) Klebsiella pneumoniae
e) Pseudomonas aeruginosa
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| rugsal
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Answer is C ? 
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| arlete
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Nitrite indicates Gram negative infection. So: B.
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| bactitech
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I agree with arlete. E. faecalis doesn't always give positive nitrate. We see many enterococcus infections. I don't always have time to check the UA results on them, however.
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| Tiff
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 Agree. gram negative converts nitrate to nitrate. No reactivity to nitrite indicates it's not gram negative. so E. faecalis choice B
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| jean robert
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Correct Answer: B
The positive leukocyte esterase test indicates the presence of neutrphils in the urine, suggesting bacterial infection. The nitrite test exploits the fact that most Enterobacteria (gram(-) enteric rods) are able to form nitrite from nitrate ; thus , the nitrite test is used to diagnose UTI.
One limitation of this method is the fact that ENTEROCOCCUS is gram (+), catalase (-) bacteria that grows on bile esculin agar that doesn t produce nitrite from nitrate but can nontheless cause UTI., just as Staph. saprophyticus can.
Enterococcal UTI are often nosocomial and classically acquired in the intensive care unit , although they can occur in other settings
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| jean robert
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Take home message:
UTI with positive leucocyte esterase test and negative nitrite test:
1.-Enterococcus faecalis
2.-Staph. Saprophyticus
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| pr20
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Thanks for a gud ques.
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| icarus
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thank you so much for this question
Kind regards,
IcarusMD
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| Interferon18
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good post Jean........small details whihc while reading you miss and in the exam foxes you completely. many thanks
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