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Community Acquisition of Clostridium difficile – Is It What We Eat?
By Stan Deresinski, MD, FACP, Clinical Professor of Medicine, Stanford, Associate Chief of Infectious Diseases, Santa Clara Valley Medical Center, is Editor for Infectious Disease Alert.
Synopsis: Clostridium difficile often contaminates retail meat and salads, but the connection with human disease has not yet been made.
Source: Gould LH, Limbago B. Clostridium difficile in food and domestic animals: A new foodborne pathogen? Clin Infect Dis. 2010;51:577-582.
A recent report described a fatal case of community-acquired C. difficile diarrhea (CDAD) in a patient receiving antibiotics for a questionable diagnosis of chronic Lyme disease.1 Community-acquired CDAD, including that caused by the putatively hypervirulent strain, NAP1/027/BI, also occurs in individuals with no prior medical contact, and its incidence appears to be increasing. Asymptomatic community carriage is reported to be in the range of 3% to 5%. The source of the acquisition of the organism in these cases has remained unknown, but among the possibilities is contact with animals, contaminated environments, and the ingestion of contaminated food.
C. difficile has been detected in river and seawater samples, as well as from swimming pools and even tap water.2 Toxigenic strains have been detected in the feces of farm animals, as well as pet dogs and cats. A Canadian national survey found C. difficile in 6.1% of ground beef samples; most were toxin producers and were related to strains known to cause disease in human.3 C. difficile also has been detected in salads. Fortunately, the density of spores in meat is low although the infectious dose for humans is unknown. Unfortunately, resistance of spores to physical eradication is significant. In fact, spores can survive standard cooking temperatures in ground beef; 20 of 20 isolates survived 71°C, the recommended temperature, for two hours..4
Despite all this, no outbreaks of CDAD have been traced to food contamination, but since CDAD is ordinarily a "two-hit" disease, requiring both acquisition of the organism and exposure to antibiotics, this is, perhaps, not too surprising. Nonetheless, the role of contamination of meats and salads remains uncertain, but it seems likely that they may be the vehicle by which asymptomatic colonization occurs among community dwellers.