Do piperacillin/tazobactam and other antibiotics with inhibitory activity against Clostridium difficile reduce the risk for acquisition of C. difficile colonization?

BACKGROUND Systemic antibiotics vary widely in in vitro activity against Clostridium difficile. Some agents with activity against C. difficile (e.g., piperacillin/tazobactam) inhibit establishment of colonization in mice. We tested the hypothesis that piperacillin/tazobactam and other agents with activity against C. difficile achieve sufficient concentrations in the intestinal tract to inhibit colonization in patients. METHODS Point-prevalence culture surveys were conducted to compare the frequency of asymptomatic rectal carriage of toxigenic C. difficile among patients receiving piperacillin/tazobactam or other inhibitory antibiotics (e.g. ampicillin, linezolid, carbapenems) versus antibiotics lacking activity against C. difficile (e.g., cephalosporins, ciprofloxacin). For a subset of patients, in vitro inhibition of C. difficile (defined as a reduction in concentration after inoculation of vegetative C. difficile into fresh stool suspensions) was compared among antibiotic treatment groups. RESULTS Of 250 patients, 32 (13 %) were asymptomatic carriers of C. difficile. In comparison to patients receiving non-inhibitory antibiotics or prior antibiotics within 90 days, patients currently receiving piperacillin/tazobactam were less likely to be asymptomatic carriers (1/36, 3 versus 7/36, 19 and 15/69, 22 %, respectively; P = 0.024) and more likely to have fecal suspensions with in vitro inhibitory activity against C. difficile (20/28, 71 versus 3/11, 27 and 4/26, 15 %; P = 0.03). Patients receiving other inhibitory antibiotics were not less likely to be asymptomatic carriers than those receiving non-inhibitory antibiotics. CONCLUSIONS Our findings suggest that piperacillin/tazobactam achieves sufficient concentrations in the intestinal tract to inhibit C. difficile colonization during therapy.