Prevalence of Antimicrobial Resistance in Intestinal Flora of Patients Undergoing Prostatic Biopsy: Implications for Prophylaxis and Treatment of Infections After Biopsy

Sir, Although it is proven that prostate infection rates after TRUS-guided biopsies are reduced with prophylactic antibiotics [1], there is widespread variation in prophylaxis used with no current consensus [2]. Fluoroquinolones are the most commonly used antibiotic but there have been reports of fluoroquinolone-resistant strains of Escherichia coli causing sepsis after biopsy [3]. This has led to a variation in local institution-based antibiotic protocols. We read with interest the article by Batura et al. [4], where the authors studied the presence of antimicrobial resistance in intestinal flora of patients undergoing TRUS-guided prostate biopsies in their London Hospital. Almost all documented infections were caused by coliforms with high resistance to ciprofloxacin and co-amoxiclav, and low levels of resistance to amikacin. Further, they found a strong correlation between the antimicrobial sensitivity of infection causing organisms and those found in rectal swabs taken before biopsy. They concluded that rectal swab cultures before biopsy could guide both prophylaxis and treatment of infections. In liaison with our Microbiology Department, in late 2010, our North London Teaching Hospital changed the prophylactic antibiotic protocol for patients undergoing TRUS-guided biopsies of the prostate. The new antimicrobial prophylaxis comprised metronidazole 500 mg orally 2–4 h before the procedure and gentamicin 160 mg i.v. immediately before the procedure. We undertook an interventional study at our District General Hospital to establish the effects of this change on our patient population; we compared a prospective group with a retrospective control. Our primary end-point was hospitalisation secondary to sepsis within 1 month of the procedure. The control group comprised 71 consecutive patients who underwent a TRUS-guided prostate biopsy over a 6 month period from November 2008 to April 2009. These patients received a similar pre- and intraoperative antimicrobial regime, with the addition of a course of oral fluoroquinolone (ciprofloxacin) for 3 days after the procedure. The interventional group consisted of 92 patients, followed over a 6 month period between February and July 2010 who were treated according to the new regimen. Both groups had comparable profiles. Any patients who did not receive the studied antibiotics were excluded. There was only one case (1.4%) of TRUS-related sepsis in the control group requiring hospitalisation compared with four (4.3%) cases in the interventional group. Of these four patients, all urine cultures were negative, although E. coli was the most frequent cause of urosepsis (two of four) found on blood cultures. All patients were admitted, treated with i.v. antibiotics and made a full and uneventful recovery. The delivery of antibiotics into the prostate is a passive process. The prostate has a high lipid solubility and minimal serum protein binding is required to enter it. Fluoroquinolones are bactericidal agents that are effective against most Gram negative microbes. They are widely distributed in tissues and are lipid soluble. They show similar bioequivalency whether administered via the oral or i.v. route and achieve high peak urinary and prostatic levels within 1–3 h of administration. Previous studies have shown a prophylactic effect as a single dose of ciprofloxacin or levofloxacin, or a 3-day course as we had previously used [1,5,6]. Our results are not statistically significant due to the relatively few participants and there is also the potential loss of patients that may have been treated for post-procedural problems at another institution or by their local GP. However, it does highlight that the use of fluoroquinolones may be of benefit in ameliorating the risk of infection after TRUS-guided biopsy of the prostate. This finding is supported in the literature by other authors [7]. As a result of our experience, we think one should approach the study by Batura et al. [4] with caution in respect to extrapolating the results to inform antimicrobial policies. Despite the proximity of our centres, the variation in the antimicrobial sensitivities of our patients’ intestinal flora is clear. As such, the adoption of rectal swabs before biopsy to guide antibiotic use, as suggested, may be appropriate. We agree that identification of antimicrobial sensitivities is a sensible course of action, while further studies regarding the ideal composition of TRUS-guided biopsy antibiotic prophylaxis, especially metronidazole with either placebo or flluoroquinolones, are conducted. Our study supports the consideration of the on-going use of fluoroquinolones as part of a prophylactic regime for TRUS-guided biopsies of the prostate. The gravity of potential septic complications warrants further evaluation and auditing of local practices, with the potential establishment of local or national recommendations and/or guidelines.