Author:
Dilworth Thomas J.,Sliwinski Jora,Ryan Keenan,Dodd Monique,Mercier Renée-Claude
Abstract
ABSTRACTVancomycin with piperacillin-tazobactam is used as empirical therapy for critically ill patients. Studies of this combination against methicillin-resistantStaphylococcus aureus(MRSA) and vancomycin-intermediateS. aureus(VISA) are limited, but β-lactams in combination with vancomycin have shown synergistic activity against MRSA and VISA. The goal of this study was to evaluate whether piperacillin-tazobactam and vancomycin were synergistic against MRSA and VISAin vitro. Bloodstream MRSA (n= 20) and VISA (n= 4) strains were selected.In vitroantimicrobial activities of piperacillin-tazobactam and oxacillin were evaluated by disk diffusion, and MICs were determined by Etest using Muller-Hinton agar with and without vancomycin at one-half the MIC. Time-kill studies evaluated 14 MRSA and all 4 VISA isolates using piperacillin-tazobactam at 300/35 mg/liter or oxacillin at 40 mg/liter alone and with vancomycin at one-half the MIC. Mean zones of inhibition for piperacillin-tazobactam and oxacillin increased with vancomycin against MRSA and VISA (P< 0.001 for all), and the MIC90decreased with vancomycin against MRSA and VISA to values meeting susceptibility criteria forS. aureus(P< 0.001 for both antibiotics against MRSA). In MRSA time-kill studies, the mean 24-h reductions in inoculum for piperacillin-tazobactam, piperacillin-tazobactam with vancomycin, and oxacillin with vancomycin were 3.53, 3.69, and 2.62 log10CFU/ml, respectively. The mean 24-h reductions in VISA inoculum for piperacillin-tazobactam, piperacillin-tazobactam with vancomycin, and oxacillin with vancomycin were 2.85, 2.93, and 3.45 log10CFU/ml, respectively. Vancomycin with piperacillin-tazobactam or oxacillin demonstrated synergistic activity against MRSA and VISA. The clinical implications of these combinations against MRSA and VISA should be investigated.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
Cited by
39 articles.
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