Effect of piperacillin/tazobactam therapy on intestinal microflora.

The effect of piperacillin/tazobactam treatment upon the intestinal microflora was studied in 20 patients with intraabdominal infections. The patients received piperacillin 4 g combined with tazobactam 500 mg q 8 h by intravenous injection for 4-8 days. Stool specimens were collected before, during and after therapy for cultivation of aerobic and anaerobic microorganisms. Six patients had measurable concentrations of piperacillin (1.2-276 mg/kg/faeces) and 4 patients tazobactam concentrations (0.8-22.2 mg/kg/faeces) in the faecal specimens during therapy. The number of enterobacteria and enterococci slightly decreased while there were no changes in the number of staphylococci and bacilli. The anaerobic microflora was also slightly affected. There was a minor decrease in the number of bifidobacteria, eubacteria, lactobacilli, clostridia and veillonella but the numbers of anaerobic Gram-positive cocci and bacteroides were not influenced by the treatment. After therapy, the aerobic and anaerobic microflora returned to normal levels in all patients. None of the patients had Clostridium difficile or cytotoxin in the stools or developed diarrhoea.