In 2010, an outbreak of Clostridium perfringens at a psychiatric hospital in Louisiana claimed the lives of 3 of the 54 people sickened, an unusually high death toll for a bacteria with an average fatality rate of .03 percent of those it infects. After studying this and two other deadly C. perfringens outbreaks at psychiatric hospitals, researchers now believe that psychiatric inpatients may be at a higher risk for severe illness from this foodborne bacterium, so extra precaution should be taken when preparing food for that population. These findings were published Thursday in the Morbidity and Mortality Weekly Report put forth by the U.S. Centers for Disease Control and Prevention (CDC). One explanation for the higher death rate in the 2010 Louisiana outbreak may have been that those who died – all residents – were taking psychiatric medications whose side effects include decreased activity of the intestines, researchers found. Since C. perfringens is harbored in the intestine, decreased intestinal function can slow the process of eliminating these toxins. This prolonged exposure to C. perfringens toxins can lead to infection of the large intestine, a condition called necrotizing colitis. Autopsies of the 3 patients who died revealed that two had necrotizing colitis. The third, however, showed no signs of this condition. “One patient who died in the outbreak had no evidence of necrotizing colitis or other abnormality on postmortem examination, raising the possibility that a systemic effect of clostridial toxin plays a role,” say the authors. In other words, the effect of these toxins on the whole bodily system, rather than on just one site such as the intestine, may impact the severity of a patient’s illness. Another indication that taking medications with anticholinergic (colon-slowing) side effects may not necessarily lead to a more severe illness is that many patients who were taking these drugs made a full recovery. This fact, however, does not prove that such drugs have no effect on the course of a C. perfringens infection. The amount of medication given to patients, as well as a difference in people’s susceptibility to anticholinergic side effects, may play a role in the severity of illness, they note. For now, “The precise mechanism causing death remains in question,” says the report. Despite this persisting question, the authors say there is still strong evidence of a connection between psychiatric hospitals and worse illness from C. perfringens infection. “The results of this investigation suggest that psychiatric inpatients, especially those with constipation, are vulnerable to severe outcomes from C. perfringens intoxication,” says the report. The 2010 outbreak – which sickened 42 residents and 12 staff members – is thought to have originated with contaminated chicken salad that was not properly stored between cooking and serving. The chicken was cooked 24 hours before the meal at which it was served, and was not cooled quickly enough after preparation to prevent the growth of bacteria. Genetic analysis of toxins isolated from the chicken revealed the presence of Clostrdium perfringens type A. “This outbreak underscores the need for strict food preparation guidelines at psychiatric inpatient facilities and the potential risk for adverse outcomes among any patients with impaired intestinal motility caused by medications, disease, and extremes of age when exposed to C. perfringens enterotoxin,” reads the report. The 2010 outbreak was the second reported outbreak of Clostridium perfringens type A in a U.S. psychiatric hospital. The first occurred in 2001. Of the 7 people sickened in that outbreak – all of whom were residents – 3 developed necrotizing colitis, and 2 out of those 3 died. Researchers also point to an outbreak of C. perfringens type A at a psychogeriatric hospital in England. Two patients died in that outbreak, but neither were found to have necrotizing colitis. The full MMWR report, including profiles of the patients who died in the 2010 outbreak, is available on CDC’s website.