Rectal swab cultures guide targeted antibiotic prophylaxis after prostate biopsy

August 1, 2011

Targeted antimicrobial prophylaxis based on microbiologic findings from rectal swab cultures significantly reduces the incidence of post-transrectal ultrasound-guided prostate biopsy (TRUSP) infectious complications and has the potential to decrease the overall cost of care.

The increasing prevalence of antibiotic-resistant Escherichia coli worldwide has prompted researchers to investigate the importance of this organism as a pathogen in infectious complications after TRUSP and to develop antibiotic prophylaxis strategies for minimizing these potentially serious events.

To this end, researchers from Northwestern University Feinberg School of Medicine, Chicago evaluated 451 men who underwent TRUSP between July 2010 and March 2011. Rectal swabs were obtained for culture and sensitivity testing from 117 patients considered at risk for colonization with fluoroquinolone-resistant flora based on history features (eg, health care worker, recent exposure to ciprofloxacin [Cipro, Proquin XR], or hospitalization, diabetes, or other immunocompromised state).

The remaining subgroup of 334 men, which included men with and without risk factors for fluoroquinolone-resistant bacteria, received standard empiric prophylaxis comprised of a Fleet enema with two oral doses of ciprofloxacin, the first given 2 hours prior to TRUSP and the second 12 hours after the procedure.

Infectious complications after TRUSP were absent among the men who received targeted antimicrobial prophylaxis but developed in eight (2.4%) of the 334 patients who had empiric prophylaxis. Of the eight patients, seven had infections due to a fluoroquinolone-resistant pathogen, including one patient with sepsis, reported first author Aisha Taylor, MD, a urology resident at Northwestern who worked on the study with Anthony J. Schaeffer, MD, and colleagues.

Technique may reduce cost of care

"Not only do we think targeted antimicrobial prophylaxis is an effective strategy to reduce infectious complications after TRUSP, but we believe this low-cost screening method can also significantly reduce cost of care," Dr. Taylor said. "According to an analysis we conducted that included charges for the rectal swab ($23) and the most expensive medication used as alternative antibiotic prophylaxis, the cost for treating 100 men undergoing TRUSP was calculated as $1,323 using the targeted approach versus $5,066 for empiric prophylaxis."

Dr. Schaeffer, professor and chairman of urology at Northwestern, is senior author of the paper and was co-moderator of the AUA session where it was presented. Highlighting the seriousness of the problem of fluoroquinolone-resistant E. coli infections, he referred to the patient who developed sepsis caused by fluoroquinolone-resistant E. coli and noted he required hospitalization in the ICU for 6 weeks.

"Selecting antibiotic prophylaxis based on guessing about the risk of having fluoroquinolone-resistant flora is not a good idea," Dr. Schaeffer said. "Our study indicates that by knowing what the flora is for each patient, prophylaxis can be directed effectively. However, our study was small, and we are now seeking to confirm the value of this approach in a large, prospective, multi-institution study."