[In vitro activity of beta-lactam agents and beta-lactamase inhibitors in clinical isolates of Acinetobacter baumannii].

Acinetobacter is a Gram-negative coccobacillus frequently associated with nosocomial infections, especially pneumonia in patients using mechanical ventilators in ICUs. Many of the clinical isolates of Acinetobacter baumannii are now resistant to most antibiotics, including the betalactams, making these infections difficult to treat. We compared the in vitro activity of betalactam agents (ampicillin, piperacillin and ticarcillin), betalactamase inhibitors (clavulanic acid, sulbactam and tazobactam) alone and in combination with betalactam agents (amoxicillin-clavulanic acid, ampicillin-sulbactam, piperacillin-tazobactam and ticarcillin-clavulanic) against 156 clinical isolates of A. baumannii using an agar dilution method. In general, we observed a low susceptibility to the betalactam agents tested (ampicillin: 1.9% susceptibility; piperacillin: 10.2%; ticarcillin: 19.8%). We did not observe a significant reduction of the MIC in the combination of betalactam agents and betalactamase inhibitors; only ampicillin/sulbactam showed a high antimicrobial activity (84.6% compared to 14.1%, 37.8% and 33.9% for amoxicillin-clavulanic acid, piperacillin-tazobactam and ticarcillin-clavulanic acid, respectively). Sulbactam was the only betalactamase inhibitor which showed good in vitro activity, with a low MIC(50) and MIC(90) (8 and 32 mg/l, respectively) similar to ampicillin/sulbactam (2 and 16 mg/l, respectively). Sulbactam could be a good therapeutic alternative for the treatment of multiresistant A. baumannii infections.