Testing for Drug-Resistant Bacteria Before Prostate Biopsy Reduces Infection

Some infections after prostate biopsy due to drug-resistant Escherichia coli can be thwarted by simple rectal swab cultures prior to the procedure and the cultures test for antibiotic-resistant E. coli can be used to direct the selection of antimicrobial prophylaxis used for the procedure.

Transrectal ultrasonography–guided prostate biopsy (TRUSBx) is one of the most commonly performed outpatient urologic procedures and infection is a well-established risk, including urinary tract infection (UTI), prostatitis, bacteremia, sepsis, with well-recognized complications such as hematuria, rectal bleeding, and hematospermia.

Clinicians at the Rhode Island Hospital (Providence, RI, USA) performed a retrospective study of 487 total patients, receiving prostate biopsies from February 2013 to February 2014; 314 received preprocedure rectal cultures and 173 did not. Average ages were 62.7 and 64.1 years, respectively. There was no difference in mean prostate-specific antigen value, Charlson comorbidity score, or ethnicity.

Rectal swabs were collected in the clinic, typically less than one month before TRUSBx. For fluoroquinolone resistance testing, swabs were directly cultured on both MacConkey agar with 1 μg/mL ciprofloxacin and on blood agar plates and incubated at 35 °C for 48 hours. Antibiotic susceptibilities were determined using the automated VITEK 2 machine (bioMérieux, Inc.; Hazelwood, MO, USA).

The scientists found that found that 12.8% of the patients had preexisting, drug-resistant E. coli on the rectal swab cultures. They noted that there was a lower likelihood of post-biopsy infections and a decreased adjusted risk of infectious complications for patients receiving prophylaxis based on pre-biopsy rectal swab culture results as compared to those patients who underwent the procedure without the pre-biopsy rectal swab cultures, but the differences did not reach statistical significance because of the study size. Cultures from two of these patients grew fluoroquinolone-resistant Acinetobacter junii and Pseudomonas aeruginosa.

The patients who did not have the pre-biopsy rectal swab cultures done and who developed an infectious complication after the biopsy had longer hospitalizations for post-procedure infection, three days versus 1.6 days and 40% required continued outpatient treatment with intravenous antibiotics for those infections, compared with the 16.6% of the group treated with culture-directed antibiotics.

Jessica Dai, MD, the lead author of the study said, “As men are increasingly opting for active surveillance of prostate cancer, infectious risks associated with prostate biopsy are becoming particularly relevant. We hypothesized that the incidence of infections would decline after instituting this new screening process, and they did. Not only did we see that, we also met our secondary aim of establishing the local incidence of fluoroquinolone-resistant and extended-spectrum beta-lactamase (ESBL)-producing bacteria in rectal swab cultures.” The study was published on November 20, 2014, in the journal Urology.

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Rhode Island Hospital
bioMérieux, Inc.