[Estimate of aztreonam (AZT) hydrolyzing enzymes from clinically isolated AZT-resistant gram-negative bacilli].

: The MICs of Aztreonam (AZT) against 590 clinical isolates of Gram-negative bacilli were determined. About 13.4% (79 strains) of the isolates were AZT-resistant (MIC; 12.5 micrograms/ml less than or equal to). The resistance pattern against various beta-lactams and the effects on MICs of combination of Clavulanic acid (CVA) and AZT against AZT resistant strains suggested that AZT was inactivated by either type of IV (K1), Va (OXA1), or PSE2 beta-lactamases.