Comparison of media and methods for countingClostridium perfringensin poultry meat and further-processed products

Abstract

SUMMARYA Most Probable Number (MPN) method involving Differential Reinforced Clostridial Medium followed by streaking on Willis & Hobbs medium was com pared with direct plating of samples on Tryptose-Suiphite-Cycloserine agar with out egg yolk, and two forms of Oleandomycin-Polymyxin-Suiphadiazine-Per fringens agar, one being prepared from a commercial, dehydrated product.With skin samples taken from chicken carcasses at different stages of processing, the three direct plating media gave similar counts ofCl. perfringenswhereas results obtained with the MPN method were consistently lower.Although counts ofCl. perfringensfrom various further processed products were usually < 10/g, the three plating media showed similar specificity for this organism.All media supported good growth of reference strains ofClostridium perfringensbut it was founsi that physiologically similar species, includingCl. absonum, Cl. paraperfringens and Cl. perenne alsogrew uninhibited in these media and produced colonies identical with those ofCl. perfringens, thus indicating the need for confirmatory tests forCl. perfringenswhen examining natural samples.