Effect of piperacillin/tazobactam treatment on human bowel microflora.

The effect of piperacillin/tazobactam treatment on the bowel microflora was studied in 20 patients with intra-abdominal infections. The patients were treated with piperacillin 4 g and tazobactam 500 mg administered intravenously every 8 h for four to eight days. Stool specimens were collected before, during and after treatment. Six patients had measurable faecal concentrations of piperacillin (1.2-276 mg/kg) and four patients measurable concentrations of tazobactam (0.8-22.2 mg/kg) during treatment. The mean numbers of enterobacteria, enterococci, bifidobacteria, eubacteria, lactobacilli, clostridia and Gram-positive cocci decreased while the numbers of anaerobic Gram-negative cocci and bacteroides were unaffected. The aerobic and anaerobic microflora returned to normal in all patients after the treatment had stopped.