Rectal Swab Culture–directed Antimicrobial Prophylaxis for Prostate Biopsy and Risk of Postprocedure Infection: A Cohort Study

Objective To examine the effect of rectal swab culture–directed prophylaxis on the incidence of prostate biopsy–associated infections. Secondary objectives were to determine the rate of fluoroquinolone resistance and extended-spectrum beta-lactamase production in local rectal flora. Methods All men receiving prostate biopsies from February 2013 to February 2014 were included in a retrospective institutional review board–approved study. All received either a preprocedural rectal swab and culture-directed antimicrobial prophylaxis or routine fluoroquinolone antibiotics. Clinical information was collected on infectious complications treated within 30 days of biopsy. Chi-square test, Fisher exact test, and Welch t test were used for statistical analysis. Confounding variables were included in a multivariate logistic regression model. Results Of 487 total patients, 314 received preprocedure rectal cultures and 173 did not. Average ages were 62.7 and 64.1 years, respectively (P = .07). There was no difference in mean prostate-specific antigen value (P = .9), Charlson comorbidity score (P = .8), or ethnicity (P = .1). The rectal swab group was more likely to receive supplemental gentamicin (P < .001) and had fewer infectious complications (1.9% vs 2.9%; P = .5). On multivariate analysis, decreased odds of infection was associated with culture-directed antibiotics (odds ratio, 0.70; 95% confidence interval, 0.20-2.50; P = .6). However, the study was only powered to detect a 97% reduction in infections. The incidence of fluoroquinolone resistance and extended-spectrum beta-lactamase production was 12.1% and 0.64%, respectively. Conclusion Our study was underpowered but suggests that there are lower odds of infection with rectal swab–directed antimicrobial prophylaxis. The local incidence of fluoroquinolone resistance is high. A prospective, randomized, controlled trial is warranted to further evaluate this intervention.