Heat survival of Clostridium difficile spores in ground meat during cooking process

Introduction: Clostridium difficile is a spore-forming pathogen considered as a major cause of enteric disease in humans, with faecal-oral route as the primary mode of transmission. However, recent studies have reported the occurrence of C. difficile in ground meats at retail stores, indicating that foods could be an additional source of infection in the community.
Purpose: The objective of this study was to determine the resistance of C. difficile spores in contaminated ground meat during cooking process.
Methods: Prior to testing, to obtain spores and to enhance heterogeneity, spores of two different strains were produced in two nutritious broths. C. difficile spores were experimentally inoculated in 45 g of ground meat (beef and pork) in order to obtain a final contamination of 4,500 ufc g-1. Six heating temperatures (70, 75, 80, 85, 90 and 95°C) were chosen. Samples were heating in a water bath with an integrated program for time-temperature. One sample without inoculum was used as control with a temperature probe placed inside. Once the desired temperature was research in the core of the sample, the heat treatment was prolonged for 10 min. Subsequently, all the samples were placed on the chilling room (4°C) before analyse. These experiments were conducted in duplicate with a spore enumeration in triplicate.
Results: Heating contaminated ground meat at 70, 75 and 80°C for 10 min was not effective for C. difficile spores inhibition. However, 10 min of heat shock at 80°C was the only temperature that significantly reduced the number of countable colonies. Heat treatment at 85°C (or more) inhibits the germination of both of the strains tested.
Significance: Ensure that ground meat, like burgers or sausages, is heated to more than 85°C would be an important measure to reduce the risk of C. difficile food transmission.