Piperacillin/tazobactam (YTR 830) combination. Comparative antimicrobial activity against 5889 recent aerobic clinical isolates and 60 Bacteroides fragilis group strains.

Piperacillin combined with tazobactam (formerly YTR 830) was tested at a ratio of 8:1 against 5889 aerobic isolates and 50 strains from the Bacteroides fragilis group. Imipenem was the most active agent tested against Enterobacteriaceae (99.3% at less than or equal to 4 micrograms/ml), ceftazidime was most effective against nonenteric Gram-negative bacilli (80.7% at less than or equal to 8 micrograms/ml), and piperacillin/tazobactam possessed a superior spectrum against Gram-positive cocci (92.2% at less than or equal to 16/2 micrograms/ml). Against all aerobic strains, piperacillin/tazobactam had a spectrum (90.3% at less than or equal to 16/2 micrograms/ml) comparable to imipenem (93.6% at less than or equal to 4 micrograms/ml) and was distinctly greater than that of ticarcillin/clavulanic acid (73.3% at less than or equal to 16/2 micrograms/ml) and ceftazidime (75.5% at less than or equal to 8 micrograms/ml). Against the B. fragilis group isolates, all piperacillin/tazobactam MICs were less than or equal to 64/8 micrograms/ml. This activity was superior to piperacillin alone (MIC:50, 8-64 micrograms/ml) and cefoxitin (MIC50, 4-64 micrograms/ml). Piperacillin/tazobactam appears to be a promising parenteral antimicrobial combination, with a spectrum effective against a wide variety of clinical pathogens.