title: Comparison of broth enhancement to direct plating for screening of rectal cultures for ciprofloxacin-resistant Escherichia coli.
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.
authors.affiliation: Department of Urology, University of California, Irvine, Irvine, California, USA. mliss@ucsd.edu
authors.forename: Michael A
authors.initials: MA
authors.lastname: Liss
authors.forename: Kristen K
authors.initials: KK
authors.lastname: Nakamura
authors.forename: Ellena M
authors.initials: EM
authors.lastname: Peterson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001431:Bacteriological Techniques / Q000379:methods*; D002353:Carrier State / Q000175:diagnosis* / Q000382:microbiology; D002939:Ciprofloxacin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000175:diagnosis* / Q000382:microbiology; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D012007:Rectum / Q000382:microbiology*; D012680:Sensitivity and Specificity
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin