ARS | Publication request: Prevalence and genotypic characteristics of Clostridium difficle in a closed and integrated human and swine population

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 21, 2011
Publication Date: August 1, 2011
Citation: Norman, K.N., Scott, H.M., Harvey, R.B., Norby, B., Hume, M.E., Andrews, K. 2011. Prevalence and genotypic characteristics of Clostridium difficle in a closed and integrated human and swine population. Applied and Environmental Microbiology. 77:5755–5760.

Interpretive Summary: Clostridium difficile (Cd) is a bacterium that causes disease and death in humans, and historically the infection was acquired during hospital stays. Recently, more virulent strains that are community-acquired have emerged. Although the origin of the new strains is unknown, some speculate they could be of animal origin (occupational exposure or food). In the present study, we isolated 38 Cd from humans in a closed population of humans and swine. Our results suggest a low human risk of Cd on the basis of occupational exposure and a diminished risk from food exposure to Cd. The similarity of strains between humans and swine on the same premises suggest an environmental source of exposure common to both species (i.e., soil, water, feedstuffs, feces, or other). Although not conclusive, these findings are important because they decrease the likelihood that human Cd infections come from swine or pork.

Technical Abstract: Recently, increases in cases of community-acquired Clostridium difficile have led researchers to explore additional sources of infection. The objective of this study was to compare C. difficile isolated from a closed population of both humans and swine to investigate possible food safety and occupational risks. We identified 11.8% of the human wastewater samples, and 8.6% of the swine samples were positive for C. difficile. The prevalence of C. difficile among swine production groups differed significantly (p<0.05); however, prevalence in the human occupational group cohorts did not differ (p=0.81). The majority of the human and swine isolates were of a similar strain. The similarity in C. difficile prevalence between human group cohorts suggests a low occupational hazard, and the decreased prevalence of C. difficile in late swine production groups suggests a diminished risk of food-borne exposure. However, the similarity of strains between host species provides evidence of a common environmental source.