Multidrug-resistant E. coli common prior to prostate biopsy

June 1, 2012

In men scheduled for transrectal prostate biopsy, 70% of the fluoroquinolone-resistant Escherichia coli isolated from fecal flora represented the epidemic, multidrug-resistant ST131 strain, a recent phylogenic and virulence factor analysis found.

The analysis, carried out at three U.S. institutions, also revealed a relationship between E. coli clonal strains and ethnicity.

The authors obtained fecal specimens from rectal swabs of 136 men undergoing a transrectal prostate biopsy from three Institutional Review Board-approved institutions: a Veterans Affairs medical center, a university hospital, and a private medical center, within the time period January 2009 to March 2010. The swabs were placed directly into 5 mL of brain-heart infusion broth containing 10 mg/mL of ciprofloxacin (Cipro, Proquin), incubated overnight at 35°C in ambient air, and then sub-cultured to MacConkey agar with 10 µg/mL of ciprofloxacin.

"Transrectal biopsies are one of the most common ways of diagnosing prostate cancer. Unfortunately, prostate biopsy infection has risen threefold over the past decade, likely due to fluoroquinolone resistance. Prostate biopsy patterns have also been increasing largely due to screening and active surveillance protocols and may be required in the future prior to focal therapy options. Much of prostate biopsy infection is attributed to quinolone-resistant E. coli-approximately 90%," said first author Michael A. Liss, MD, clinical instructor in the department of urology at the University of California, Irvine, working with James R. Johnson, MD, of the Minneapolis Veterans Affairs Center, and co-authors.

Dr. Liss noted no association of ST131 with veteran status, age (>65 years), or total illness burden index for prostate cancer (score >5, all p values >.05).