New media for detection and counting of Clostridia in foods

The growth of pure cultures of Clostridium perfringens (ATCC 12922) and Cl. sporogenes (PA 3679) in five non-selective media, fluid thioglycollate medium (FTM), rapid perfringens medium (RPM), Columbia broth Malthus (CBM), reinforced clostridial medium (RCM) and lactose sulphite (LS), was monitored using conductance measurements with a Malthus analyser. Only FTM and CBM gave useful results. The correlation of log(10) plate counts on blood agar of the pure strain of CI, sporogenes with detection times in FTM was highly significant (r = 0.96, n = 73), and with detection times in CBM less so (r = -0.909, n = 33). The correlation of log(10) counts on tryptose sulphite neomycin medium (TSN) of wild strains of Cl. sporogenes and Cl. perfringens with detection times with FTM in meat was also highly significant (r = 0.933, n = 54).