HEAT-STABILITY OF THE ANTIMICROBIAL ACTIVITY OF 62 ANTIBACTERIAL AGENTS

Sixty-two antimicrobial agents, including several combinations, were e xamined for stability at 56 degrees C for 30 min and 121 degrees C for 15 min, respectively. A microtiter broth dilution MIC test and an aga r disk diffusion test served to test each chemo-agent for residual ant imicrobial activity. Eleven drugs were partially heat-labile (MICs rai sed four- to eight-fold after autoclaving) and 26 drugs were heat-labi le (MICs raised greater than or equal to 16-fold following autoclaving ); the remainder proved heat-stable (MICs raised less than or equal to two-fold after autoclaving). Surprisingly, the beta-lactams, azlocill in, aztreonam, mezlocillin, and oxacillin, were remarkably heat-stable .