Prevalence of ST131 among fluoroquinolone-resistant Escherichia coli obtained from rectal swabs before transrectal prostate biopsy

Objective: To identify the prevalence and characteristics of fluoroquinolone-resistant (FQ-R) Escherichia coli ST131 isolates in men undergoing ultrasound-guided transrectal prostate biopsy (TPB).

Materials and methods: Twenty-seven FQ-R E coli isolates from rectal swabs from 136 men undergoing TPB at 3 institutions in southern California (January 2009 to March 2010), with a focus on repeat biopsy patients, were assessed for E coli phylogenetic group, sequence type ST131 status, extended virulence genotype, pulsed-field gel electrophoresis profile, and antimicrobial susceptibility profile.

Results: ST131 accounted for 70% of the 27 FQ-R pre-TPB E coli rectal isolates, including 82% of those from non-Asians vs 20% from Asians (P = .017). ST131 was associated negatively with prebiopsy enemas and positively with previous TPB. Compared with non-ST131 isolates, the ST131 isolates had a significantly higher prevalence of 4 virulence genes (sat, usp, ompT, and malX), distinctive virulence profiles, and numerically higher virulence scores (median, 12 vs 8), but similar antimicrobial resistance scores. Most rectal ST131 isolates exhibited pulsed-field gel electrophoresis profiles typical of clinical ST131 isolates.

Conclusion: In our locale, the epidemic multidrug-resistant ST131 clonal group accounts for 70% of FQ-R rectal E coli isolates among men undergoing TPB. Such ST131 isolates have distinctive virulence profiles, are extensively antimicrobial-resistant, and are negatively associated with Asian race. Further investigation is needed regarding risk factors for and clinical consequences of colonization with such strains among men undergoing TPB.