Occurrence of Clostridium perfringens in the Broiler Chicken Processing Plant as Determined by Recovery in Iron Milk Medium

Abstract

Over 30 years ago, Clostridium perfringens was reported as a contaminant of the processing plant and processed carcasses of broiler chickens. Poultry processing procedures and methods for detecting C. perfringens have changed since that time. Therefore, a study was conducted to determine the incidence and numbers of C. perfringens in the water of the scald tank, the water of the chill tank, and the rinse water of the processed carcasses from modern broiler chicken processing plants. In trial 1, collected samples were inoculated into iron milk medium (IMM) and incubated at 46°C for 18 h (the traditional method) or at 37°C for 3 h followed by incubation at 46°C for 15 h (an injury recovery method). Each of three preselected broiler chicken flocks from two integrators were the first processed for that processing shift. The overall incidence of confirmed C. perfringens in samples associated with the three flocks was 40% of postprocessing scald water samples, 13% of preprocessing chill water samples, 13% of postprocessing chill water samples, and 19% of carcass rinses. The incidence of C. perfringens in samples incubated in IMM using the injury recovery procedure was significantly higher than in samples incubated in IMM by the traditional method, but only when all samples associated with the three flocks were pooled. In trial 2, water samples from each tank of a three-tank counterflow scalder, water samples from the prechill and chill tank, and samples of carcass rinses were collected in the middle of a processing shift during multiple visits to a processing plant. Samples were inoculated into IMM with neomycin and polymyxin B sulfate (IMMA) and incubated using the traditional and injury recovery procedures. The incidence of C. perfringens in water samples was 100% from scald tank 1, 100% from scald tank 2, 100% from scald tank 3, 88% from the prechill tank, and 63% from the chill tank. The incidence in carcass rinse samples was 67%. The mean most probably number (MPN) of C. perfringens for contaminated samples decreased from log10 5.07/100 ml of water in scald tank 1 to log10 1.26/100 ml of water in the chill tank. The mean MPN in carcass rinse samples was log10 1.20 C. perfringens per 100 ml. The incidence and mean MPN of C. perfringens in these samples after heat shock at 75°C for 20 min was somewhat less, but high enough to indicate that much of the contamination arises from heat-resistant spores of this organism. In trial 2, there were no differences in incidence and MPN of C. perfringens in samples incubated in IMMA with the traditional method or the injury recovery method.