Antimicrobial susceptibility tests for anaerobic bacteria. Comparison of Wilkins-Chalgren agar reference method and a microdilution method, and determination of stability of antimicrobics frozen in broth

Abstract

Susceptibility results for anaerobic bacteria obtained with a microdilution method with either Wilkins-Chalgren broth or Brain Heart Infusion broth were compared to results obtained with the reference agar dilution method proposed by the National Committee for Clinical Laboratory Standards. Results were generally comparable, but the minimal inhibitory concentrations obtained with the microdilution method were slightly lower than those obtained with the agar dilution method. Antibiotics stored in these broths in microdilution trays at-20°C were stable for up to 130 days.