The effect of piperacillin prophylaxis on the colonic microflora In patients undergoing colorectal surgery.

Piperacillin was given parenterally in doses of 4 g every 8 h for two days to 20 patients undergoing colorectal surgery. A series of serum and fecal specimens were taken to analyse piperacillin concentrations. Tissue samples from the gut wall were taken during surgery. The maximum serum concentrations during surgery were reached 15 min after piperacillin administration. On Day 0 the mean half-life was 1.9 h and the mean area under the serum concentration curve was 536.8 mg/l. The piperacillin concentrations in the tissue samples ranged from 4.2 to 103.5 mg/kg. The tissue/serum ratio was 0.45. The piperacillin concentrations in the fecal samples ranged from not detectable to 101.2 mg/kg. Fecal samples were also collected during the investigation period for the cultivation of aerobic and anaerobic bacteria. Of the aerobic bacteria, enterococci, streptococci and enterobacteria decreased in on fourth of the patients during the prophylaxis period. Anaerobic bacteria, e. g. cocci, gram-positive rods, fusobacteria and bacteroides, decreased in two thirds of the patients during the same period. After the piperacillin administration period, the aerobic and anaerobic colon microflora returned to the pre-treatment pattern in most patients. Postoperative infections due to Escherichia coli, Morganella morganii, Bacteroides fragilis, peptococci and peptostreptococci occurred in two patients.