Epidemiology student heads to the windy city!
November 18, 2009
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
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.
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