title: Characterization of ciprofloxacin resistant Escherichia coli isolates among men undergoing evaluation for transrectal ultrasound guided prostate biopsy.
abstract: OBJECTIVE
  We determine the prevalence of ciprofloxacin resistant gram-negative bacilli in patients scheduled for transrectal ultrasound guided prostate biopsy, characterize the Escherichia coli strains recovered from this patient population, and characterize the mechanisms responsible for β-lactam and ciprofloxacin resistance.
  
  
  METHODS
  Rectal swabs from 991 patients were cultured for ciprofloxacin resistant gram-negative bacilli with a selective medium. Recovered E. coli isolates were further analyzed with susceptibility testing, pulsed field gel electrophoresis, plasmid isolation and sequencing.
  
  
  RESULTS
  A total of 193 ciprofloxacin resistant gram-negative bacilli were recovered and of these isolates 167 (87%) were E. coli. The prevalence of ciprofloxacin resistant E. coli in the study population was 17%. Only 38 (26%) of the 149 E. coli isolates that received susceptibility testing were susceptible to ampicillin and ampicillin-sulbactam. In select isolates transferrable plasmids carrying β-lactamase were responsible for the resistance to the β-lactam agents and other nonβ-lactam antimicrobials. Diverse combinations of gyrA and parC mutations associated with fluoroquinolone resistance were identified. Strain typing and plasmid typing indicated that the E. coli isolates did not share a common origin.
  
  
  CONCLUSIONS
  Of the patients in our study 17% carried ciprofloxacin resistant E. coli. Analysis of resistance mechanisms and plasmid analysis along with strain typing demonstrated that this patient population harbored organisms with heterogeneous phenotypic susceptibility, indicating that universal prophylaxis would not provide optimal coverage for patients undergoing transrectal ultrasound guided prostate biopsy.
authors.affiliation: Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois; Clinical Microbiology Laboratory, Northwestern Memorial Hospital, Chicago, Illinois. Electronic address: cqi451@northwestern.edu.
authors.forename: Chao
authors.initials: C
authors.lastname: Qi
authors.forename: Michael
authors.initials: M
authors.lastname: Malczynski
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Schaeffer
authors.forename: Grace
authors.initials: G
authors.lastname: Barajas
authors.forename: Robert B
authors.initials: RB
authors.lastname: Nadler
authors.forename: Marc H
authors.initials: MH
authors.lastname: Scheetz
authors.forename: Teresa R
authors.initials: TR
authors.lastname: Zembower
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001706:Biopsy / Q000379:methods; D002939:Ciprofloxacin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects*; D006801:Humans; D061705:Image-Guided Biopsy; D008297:Male; D008826:Microbial Sensitivity Tests; D011467:Prostate / Q000473:pathology*; D012007:Rectum; D018084:Ultrasonography, Interventional
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin
keywords: CLSI; Clinical and Laboratory Standards Institute; ESBL; FQ; MAC; MIC; MacConkey; PFGE; QRDR; SXT; TRUSP; biopsy; drug resistance; extended spectrum β-lactamase; fluoroquinolone; fluoroquinolones; infection; microbial; minimal inhibitory concentration; prostate; pulsed field gel electrophoresis; quinolone resistance-determining region; transrectal ultrasound guided prostate biopsy; trimethoprim-sulfamethoxazole