Trimethoprim versus Gentamicin for the Prevention of Bacteriuria following Transrectal Biopsy of the Prostate – Do Patients Need Additional Anaerobic Cover?

Abstract

Objectives: To study the incidence of aerobic and anaerobic bacteriuria in patients undergoing transrectal ultrasound-guided biopsies of the prostate. A comparative assessment of efficacy of trimethoprim with gentamicin for the prevention of bacteriuria following the transrectal biopsy of the prostate. To assess the need for additional prophylaxis against anaerobes for patients undergoing transrectal biopsies of the prostate gland. Patients and Methods: In a pilot study during 1995–1997, all the patients undergoing transrectal ultrasound-guided biopsy of the prostate were randomised to receive either trimethoprim or gentamicin prophylaxis prior to the procedure. Midstream urine (MSU) samples were taken just prior to biopsy and 72 h later. A patient questionnaire to determine the symptoms of urinary tract infection (UTI) accompanied the 72-hour MSU request form. Urine samples were cultured aerobically, using a semiquantitative technique if dipstick analysis revealed the presence of blood, pus cell or nitrite. In addition to the routine aerobic culture, post-biopsy samples were also cultured for anaerobes by direct and enrichment methods. Bacteriuria was defined as a pure or mixed growth of 10⁵ colony-forming units/ml. Fisher’s test of exact probability was used for statistical analysis. Results: 115 patients were available for final analysis. 53 had received gentamicin and 62 trimethoprim. Four patients had pre-existing bacteriuria (3.5%), 3 in the trimethoprim group and 1 in the gentamicin group. Post-operative bacteriuria developed in 5 patients given gentamicin (9.4%) and 1 given trimethoprim (1.6%). This difference was not statistically significant (p = 0.085). Post-procedure bacteriuria was asymptomatic in all but 1 case. Anaerobes were detected in only 5 MSUs (4.3%) post-biopsy. Conclusion: Though there was no statistical significant difference in the rates of bacteriuria following administration of trimethoprim and gentamicin, data appear to favour trimethoprim prophylaxis. Further studies are warranted. Transrectal biopsy of the prostate is associated with a low incidence of anaerobic UTI. In view of the very low incidence of anaerobic bacteriuria, routine antibacterial prophylaxis against anaerobes does not appear to be justified.