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J Clin Microbiol. 2013 Jan;51(1):249-52. doi: 10.1128/JCM.02158-12. Epub 2012 Nov 14.

Comparison of broth enhancement to direct plating for screening of rectal cultures for ciprofloxacin-resistant Escherichia coli.

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1
Department of Urology, University of California, Irvine, Irvine, California, USA. mliss@ucsd.edu

Abstract

A transrectal prostate biopsy is the most common procedure used to establish the diagnosis of prostate cancer. Prior to biopsy, patients are commonly given ciprofloxacin for prophylaxis. However, a complication of the procedure is infection with ciprofloxacin-resistant organisms, in particular resistant Escherichia coli. In order to identify patients carrying ciprofloxacin-resistant E. coli, so as to tailor their antibiotic prophylaxis, rectal swabs are screened using selective broth and/or solid medium. In our evaluation, we compared broth enrichment and direct plating techniques by using brain heart infusion broth and MacConkey agar containing 1 μg/ml or 10 μg/ml of ciprofloxacin. Of the 100 patients included in the study, 20 were colonized with ciprofloxacin-resistant organisms, 19 of which were E. coli. There was no significant difference (P > 0.1) between the culture methods or the ciprofloxacin concentrations in the medium when identifying patients with ciprofloxacin-resistant E. coli; however, broth enrichment using 1 μg/ml ciprofloxacin was the most sensitive at 100%, but it was the least specific. Direct plating of rectal swabs onto MacConkey agar containing 10 μg/ml of ciprofloxacin was 100% specific and missed only 1 positive specimen, with a sensitivity of 94.7%; this method was the most cost-effective. Therefore, direct plating of rectal swabs onto selective medium proved to be a sensitive and cost-effective approach in identifying patients colonized with ciprofloxacin-resistant E. coli.

PMID:
23152550
PMCID:
PMC3536248
DOI:
10.1128/JCM.02158-12
[Indexed for MEDLINE]
Free PMC Article
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