Genetic profiling of little benefit in detecting fluoroquinolone-resistant bacteria

The use of polymerase chain reaction (PCR)-based molecular profiling does not boost the detection rate of fluoroquinolone-resistant (FQR) microbes before transrectal prostate biopsy, a new study has found.

Researchers conducted a prospective observational cohort analysis of 72 patients, from whom rectal swabs were collected within 30 days before an upcoming prostate biopsy. Swabs underwent phenotypic culture assessment, along with PCR-based genotypic analysis, to predict the FQR rate on biopsy day.

Overall, 17 patients showed resistance on the day of the procedure, yielding an FQR prevalence rate of 23.6 percent. Bacterial culture analysis had a sensitivity of 88 percent and a specificity of 95 percent for predicting FQR at biopsy day. A rectal swab culture frown on a ciprofloxacin-infused MacConkey agar produced the best predictive value for FQR, with an area under the curve (AUC) of 0.85.

Meanwhile, genetic FQR, as determined by the presence of plasmid qnr genes, was detected in 54.1 percent (n=39) of participants.

However, receiver operating characteristic curve analysis revealed that despite having a good overall specificity (87 percent), genotype assessment of FQR had poor sensitivity (12 percent). PCR screening, taking into consideration all FQR genes including but not limited to qnr, had a maximum AUC of 0.45, suggesting no added benefit of this approach.

“The genotypic assessment of bacteria did not reflect the bacterial resistance profile for fluoroquinolones in this study. We detected a high prevalence of FQR-associated plasmids along with a known uropathogenic strain of Escherichia coli,” the researchers said.

“These results could be very concerning for the future of quinolone antibiotics and encourage alternative strategies to augment antibiotics before prostate biopsy selectively or use transperineal approaches to avoid the rectum,” they added.