Evaluation of four newer antimicrobial agents in the Avantage susceptibility test system

Antimicrobial elution disks containing amoxicillin-clavulanic acid (Augmentin), cefotetan, ciprofloxacin, or norfloxacin were tested in the Avantage automated susceptibility test system. Performance was compared against an agar diffusion procedure in a three-site collaborative study. Results of 1,500 comparison with amoxicillin-clavulanic acid showed a full accord (agreement of both systems) of 93.6% and an essential accord (agreement excluding minor discrepancies) of 97.6%. Results for cefotetan showed a full accord of 95.1% and an essential accord of 98.3% by the two methods. Results for both ciprofloxacin and norfloxacin were in full accord for more than 98% of tests with gram-negative bacilli and staphylococci, but tests with enterococci gave 38 and 26.1% minor discrepancies (the result of one method was resistant or susceptible and the result of the other method was intermediate), respectively. The results indicated that the Avantage test system is accurate and reliable and provides appropriate determination of bacterial susceptibility with the four antibiotics tested.