The Clostridium perfringens outbreak that occurred in early May at Central Louisianna State Hospital was recently linked to contaminated chicken salad. 40 people were sickened in the outbreak, and three people died.  So what went wrong?  Environmental health findings–i.e. the investigation at the hospital’s kitchen–have not yet been released, but the outbreak almost certainly occurred as a result of improper food handling procedures. 

Clostridium perfringens is a very common pathogen in foodpoisoning outbreaks; some estimates set clostridium perfringens as the third most common cause of foodpoisoning illnesses. Most clostridium perfringens outbreaks are ultimately linked to contaminated meat, and many such outbreaks occur after holiday meals.  The reason?  The cooking of whole fowl species, such as chicken and turkeys, that are cooled improperly after cooking.  For instance, the CDC reported on a clostridium perfringens outbreak in 2008 that occurred at a Wisconsin jail, stating as follows regarding the environmental investigation at the jail’s kitchen:

On August 8, the environmental health sanitarian from the local health department met with jail kitchen supervisors and employees of the food distribution company to assess food preparation and employee health and hygiene practices. The macaroni and ground beef in the implicated casserole were cooked the day before. The sanitarian determined that food temperatures had not been obtained or recorded consistently, and documentation of cooling temperatures for both the ground beef and macaroni, where cooling from 70°F to 41°F (39°C to 23°C) is a vital step, could not be provided. An inspection of the cooler revealed improper handling and cooling of taco meat, which was being prepared for a future meal and was not implicated in this outbreak; some containers of meat were cooled with ice paddles and other containers were not. 

It has not yet been publicly disclosed how the chicken in the chicken salad at the Louisianna hospital was prepared . . . or cooled.  It is possible that the chickens were cooked whole, and cooled improperly, or that the chicken salad was cooled improperly after it was assembled.  It is unlikely that the mayonnaise, vegetables, or spices that were included in the chicken salad were contaminated prior to assembly.

Whatever the case, somehow the clostridium perfringens bacteria–more specifically, the bacterial spores that release the illness-causing toxins–in the bad chicken was allowed to grow or replicate, leading to the bacterial proliferation that was surely the cause of this widespread outbreak.  An abstract from a recent article on the growth of clostridium perfringens bacteria during improper cooling states as follows:

Many meat-based food products are cooked to temperatures sufficient to inactivate vegetative cells of Clostridium perfringens, but spores of this bacterium can survive, germinate, and grow in these products if sufficient time, temperature, and other variables exist. Because ingestion of large numbers of vegetative cells can lead to concomitant sporulation, enterotoxin release in the gastrointestinal tract, and diarrhea-like illness, a necessary food safety objective is to ensure that not more than acceptable levels of C. perfringens are in finished products. As cooked meat items cool they will pass through the growth temperature range of C. perfringens (50 to 15 degrees C). Therefore, an important step in determining the likely level of C. perfringens in the final product is the estimation of growth of the pathogen during cooling of the cooked product.