COMPARATIVE ACTIVITIES OF PIPERACILLIN AND TAZOBACTAM AGAINST CLINICAL ISOLATES OF LEGIONELLA SPP

We evaluated the in vitro activity of piperacillin alone or in combina tion with the beta-lactamase inhibitor tazobactam against clinical iso lates of Legionella species. At an inoculum of approximately 10(4) CFU , tazobactam, piperacillin, and the 8:1 combination had equivalent act ivities against Legionella spp. At an approximately 10-fold higher ino culum, the following results were obtained, expressed as MICs for 50 a nd 90% of strains tested (MIC range): piperacillin, 4 and 16 (0.25 to 32) mug/ml; tazobactam, 0.5 and 1 (0.125 to 2) mug/ml; and piperacilli n-tazobactam (expressed in terms of MIC of piperacillin) 0.5 and 1 (0. 03 to 2) mug/ml. Tazobactam alone and the combination with piperacilli n were more active than piperacillin alone at the higher inoculum.