Anaerobic susceptibility tests. Evaluation of the stability of antimicrobials in Wilkens-Chalgren broth and the effect of media prereduction.

The stability of eight antimicrobial agents in WILKENS-CHALGREN broth was evaluated. The activities of only carbenicillin and benzyl penicillin were significantly decreased after storage for eight weeks at--20 degrees C. Anaerobic reduction of the susceptibility testing broth prior to inoculation was found to be unnecessary.