Epidemiology student heads to the windy city!

Keri Norman will present her dissertation work at the Conference of Research Workers in Animal Diseases in Chicago, IL, December 6-8, 2009. Keri is a PhD candidate investigating the possible food safety and occupational risks associated with Clostridium difficile and swine.

Abstract

Comparison of the prevalence and genotypic characteristics of Clostridium difficile in a closed and integrated human and swine population in Texas

K.N. Norman1*, H.M. Scott2, B. Norby1, R.B. Harvey3, M.E. Hume3, K. Andrews3 1Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX. 2Department of Diagnostic Medicine / Pathobiology, Kansas State University, Manhattan, Kansas. 3Food and Feed Safety Research Unit, Agricultural Research Service, USDA, College Station, TX.


The potential for C. difficile to be a food borne pathogen is an issue of current debate. One of the possible sources is thought to be swine. We have found the prevalence of C. difficile in groups of late production swine to be low (3.9%) and this might suggest a low food safety risk. The objective of this study was to compare the prevalence and genotypic characteristics of C. difficile in a closed population in Texas consisting of both human and swine populations from 2004 to 2006 in order to investigate the possible food safety and occupational risks associated with swine and C. difficile. Isolation of C. difficile was performed utilizing an enrichment technique and restrictive media. PCR was used to test for the presence of the toxin A and B genes, the tcdC gene deletion, and the binary toxin gene. Genotypic characteristics were compared using PCR toxinotyping and PFGE. We tested 2,292 aggregated human wastewater samples from 2004 to 2006 and found 271 (11.8%) to be positive for C. difficile. The prevalence of C. difficile in worker (12.0%) and non-worker group cohorts (11.6%) did not differ significantly (p=0.81). The majority (84.5%) of the wastewater isolates belong to Toxinotype V. PFGE showed about 5 different patterns but there were two dominant patterns. We have found that the majority of our swine isolates also belong to Toxinotype V and the same two dominant PFGE patterns. The similarity in prevalence between swine workers and non-workers show a low occupational hazard of working with swine and C. difficile infection. We have found that there is a decreased prevalence of C. difficile in late production groups in swine; however, the isolates derived from human wastewater appear to be of a very similar Toxinotype and PFGE pattern to those found in swine.