In vitro effect of YTR (tazobactam) on plasmid and chromosomally mediated beta-lactamases.

The effect of tazobactam on the piperacillin susceptibility and on the beta-lactamase activity of different strains and species was evaluated. A synergistic effect was observed on the piperacillin susceptibility for all microorganisms tested, irrespective of the type and/or amount of beta-lactamase produced. Addition of gentamicin resulted in a further reduction of the piperacillin MIC. The enzyme activity after induction with piperacillin alone or in combination with tazobactam (4 mg/l) was quite similar.