usmleasr
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A 3-year-old girl with a history of hydrocephalus is brought to
the neurologist by her parents with a severe headache and fever.
The girl underwent a revision of a ventricular-peritoneal shunt 1
month ago, and the neurologist suspects that an infection has occurred
. Which of the following organisms would most likely be isolated from
the shunt tubing?
A. Bacteroides fragilis
B. Corynebacterium diphtheriae
C. Escherichia coli
D. Staphylococcus epidermidis
E. Streptococcus pneumoniae
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| mistral92
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A. Bacteroides fragilis?
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| usmleasr
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nope
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| asmi
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D staph.epidermidis/saprophyticus
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| usmleasr
Forum Guru
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yes u r correct :P
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| bactitech
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Please realize that most labs do not speciate Staphylococci that are not aureus. They are now reported out as "coagulase negative staphylococcus". S. saprophyticus is usually only speciated in positive urines of reproductive age females, and not all labs run the extra disc (novobiocin) to split this off.
CNS is a major problem with infected shunts.
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Clinical Microbiology since 1974
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| Malaysian
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Can anyone tell me why is the answer the staph species and not the others?And bactitech you mentioned novobiocin.....what is the inference from this test?
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| bactitech
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No inference - we just use this disc to differentiate between S. saprophyticus and other CNS.
http://www.gpnotebook.co.uk/cache/-2012872683.htm
Skin flora plays a big part in cath tip contamination. There are many strains of CNS. Obviously the cath tips go through the skin. Slime layers can build up on cath tips which are fertile breeding grounds for bacteria.
We receive many cath tips for culture upon removal from the patient. We ID anything that grows if it's over 15 colonies on the plate, but we add a caveat comment that explains that growth must be correlated with any positive blood culture the patient might have. Many times, organisms are isolated from the cath tips that don't grow in blood cultures.
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Clinical Microbiology since 1974
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| Malaysian
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Thanks once again bactitech.
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