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MCQs in Tropical Medicine

Rob Skelly DTM+H FRCP

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Answer 24

Staphylococcus epidermidis

False a. is coagulase positive
False b. on microscopy are Gram positive cocci in chains
False c. are usually sensitive to penicillin
False d. grown in blood cultures are due to contamination and should be ignored
True e. are destroyed by povodine iodine

Staph. epidermidis is part of the normal skin flora. As for Staph. aureus, Gram positive cocci in bunches are seen on microscopy.

It is usually insensitive to penicillin.

Although it is often a contaminant in blood cultures, it is associated with line infections. Central venous catheters are an especially likely site of infection even in the absence of overt exit site sepsis. They should not be ignored but interpreted in the clinical context, and usually the blood cultures should be repeated.

In patients with central lines, blood cultures should be taken both peripherally and from the central line as semi-quantitative microbiological techniques are available that may point to the central line as the principle site of infection.

Copyright: Rob Skelly 2006