Spores of C. difficile, like those of C. perfringens, can occur in meat and survive temperatures and times recommended for cooking.
C. perfringens is a major cause of foodborne illness but studies are needed to determine whether C. difficile transmission by a similar route is a cause of infection.
C. difficile is found in the intestinal tract of food animals, such as pigs, cattle and poultry, and in some retail raw meat samples in North America and Europe.
The Institute for Food Research’s (IFR’s) Emeritus Fellow Dr Barbara Lund and Professor Mike Peck looked at the common features of C. difficile and C. perfringens relevant to foodborne transmission.
Possible foodborne transmission
Lund told FoodQualityNews that there is not much practical work in the area.
“For Clostridium perfringens the organism was identified as causing food poisoning in the 1940s-1950s, you could find a patient showing infection signs and excreting high numbers of the organism or food left to check but often the food is eaten or discarded," she said.
“We need to see if [C. difficile] would survive and what numbers are there, if it is found to survive and multiply in cooled meat products then we need to ask if the dose is enough to cause infection in humans.
“First we need to check the sensitivity of the methods for isolating, C. difficile is difficult to culture. Then we must determine the temperature the organism grows at, as we don’t know the maximum and minimum temperatures, or the rate of growth.
“We then have cause to gather momentum of the potential problem and put it into context, either it is a problem or it is not a problem.”
Lund said further work would involve growing it in controlled culturing conditions to see its foodborne potential.
C. difficile and C. perfringens type A occur in meats, vegetables and shellfish.
If cooked meat foods are allowed to remain at temperatures between 12C and 50C after cooking, spores of C. perfringens that have survived the process can germinate and result in growth of vegetative bacteria.
C. difficile is liable to survive cooking of meat and other foods to a core temperature of 74°C or to 70°C for up to two minutes.
They may germinate and allow growth of vegetative bacteria if cooked food is maintained at permissive temperatures, or they may remain as resistant spores.
Optimum temperature for growth is 30°–37°C, and it grows at 25°C and 45°C (Rainey et al., 2009), but there is a lack of information on minimum and maximum temperatures allowing growth, and rates of growth.
For C. perfringens there is information on temperatures allowing germination and growth and rates of growth, which allows temperature controls to be known and a cooling regimen to prevent growth.
Information such as further data on the range of temperatures that allow growth and the effect of temperature and optimum culture medium for maximum recovery of heated and unheated spores and vegetative bacteria is needed to assess the risk of transmission and, if necessary, devise conditions to prevent it.
Source: Foodborne Pathogens and Disease
Online ahead of print, doi: 10.1089/fpd.2014.1842
Authors: Barbara M. Lund and Michael W. Peck