Date Full Report Received02/08/2011
Date Abstract Report Received02/08/2011
InvestigationInstitution: Food and Feed Safety Research Unit, USDA-ARS-SPA
Primary Investigator: Roger B. Harvey
Funded ByNational Pork Board
In recent years, there has been increased incidence and severity of human disease associated with the bacterium Clostridium difficile (Cd). It appears that epidemic disease is being caused by newly emerging strains of Cd. No one knows where the new strains came from, but it is speculated that some human disease strains may have come from pigs or could be food-associated (maybe from pork). In another study funded by NPB Grant #06-156, the authors showed that the majority of Cd isolates from swine came from suckling piglets in the farrowing barn, whereas a very low percentage of isolates were found in market age pigs. This suggested that pork posed a low risk for exposure to Cd. In the present study, we proposed to determine what the prevalence of Cd was in a human population that lived at the same locations as pigs. Besides consuming pork produced in this integrated system, a portion of the humans were swine workers. We compared the prevalence of Cd between workers and non-workers to see if there was an occupational risk from regular contact with swine. We also wanted to evaluate the genetic similarity or relatedness of Cd isolates from swine compared to human isolates. We isolated 38 Cd from 668 human wastewater samples. Most of the isolates were similar to ones we had isolated from pigs, although there were human isolates that were not found in pigs. There was no difference between swine workers and non-workers nor were there differences in human isolations based on farms where swine had high Cd prevalence. These results suggest that risk of Cd infection is not an occupational one and there does not appear to be evidence that Cd is food-associated. The authors conclude that the similarity of Cd strains found in both humans and swine on the same premises suggest an environmental source of exposure common to both species (i.e., soil, water, feedstuffs, feces, other).