Friday, July 25, 2008


Routine blood cultures are drawn on an otherwise healthy 20 year old man enrolled in a research study. Cultures are drawn from 2 sites on different arms. The culture from the left arm is negative. The culture from the right arm shows the above image after 72 hours. The study subject does not have fever, hypotension, leukocytosis, or any other detectable laboratory abnormalities.

Challenge: What antibiotic (or class of antibiotic) would you prescribe?

Related Questions:
1. What is the organism shown above?

Image shown under fair use.

1 comment:

Craig said...


The image shows gram + cocci in clusters. The history suggests that this is Staphylococcus epidermidis due to contamination (thus, no antibiotics). Only 4-12% of patients with positive blood cultures for coagulase negative Staphylococci have significant bacteremia. This would be suggested by symptoms of infection, growth in culture within 48 hours, and multiple positive cultures with the same antibiograms.

Sources: UpToDate;