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Reducing Blood Culture Contamination

Blood culture results often represent contaminants rather than true bacteremia. Adequate preparation of the skin prior to venipuncture can reduce contamination, but the best choice of antiseptic is not known. In this randomized trial, French researchers compared an alcoholic solution of 0.5 percent chlorhexidine gluconate with an aqueous solution of 10 percent povidone-iodine for skin preparation. The solutions were applied vigorously, and blood was drawn 15 to 30 seconds later.

Of 2041 blood cultures drawn from 403 intensive care unit patients, 124 grew bacteria; 48 of these cultures grew contaminants (mostly coagulase-negative staphylococci). Contamination was classified as such by 2 reviewers who were unaware of which preparation group yielded the culture. Significantly more cultures taken after povidone-iodine application were contaminated (3.3 percent vs. 1.4 percent).

Comment: In this study, funded in part by the manufacturer, chlorhexidine was superior to povidone-iodine. This finding may be explained by the short time between application and phlebotomy (favoring the alcoholic chlorhexidine), biases in this single-blind study (different antiseptic colors), or a true difference in efficacy. If subsequent studies address these questions, and if chlorhexidine proves to be more cost-effective, it would make sense to use this preparation.

— R Saitz

Published in Journal Watch General Medicine December 24, 1999

Citation(s):

Mimoz O et al. Chlorhexidine compared with povidone-iodine as skin preparation before blood culture: A randomized, controlled trial. Ann Intern Med 1999 Dec 7 131 834-837.

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