Evaluation of cycloserine-cefoxitin-fructose agar and cycloserine-cefoxitin-fructose broth for recovery of Clostridium difficile from environmental sites

Abstract

Cycloserine-cefoxitin-fructose agar (CCFA) and cycloserine-cefoxitin-fructose broth (CCFB) containing either 500 or 250 μg of cycloserine per ml were compared for efficacy in the isolation of Clostridium difficile from hospital ward environmental sites. A RODAC imprint technique was used to inoculate prereduced CCFA. Moistened swabs were used to inoculate prereduced CCFB from environmental sites immediately adjacent to the RODAC sample sites. CCFA (6% positive) was significantly more sensitive than CCFB (3% positive; P < 0.005), regardless of the cycloserine concentration. When the CCFA cycloserine concentration was decreased from 500 to 250 μg/ml, the overall rate of positive cultures rose from 4 to 17%. Medium containing 500 μg of cycloserine per ml may be too inhibitory to isolate many moderately sensitive strains of C. difficile from environmental sites. Regardless of the cycloserine concentration, the CCFA RODAC imprint technique is superior to the CCFB method.