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Recently there has been an epidemic of human disease in North America caused by the bacterium Clostridium difficile (Cd). It appears to be a new strain that is more virulent than previous strains, produces more toxins, and causes more severe disease. The origin of the new strain is unknown. Genetic analysis indicates that the new strain is 80% related to some swine Cd isolates. Cd has been isolated from retail pork. No epidemiological information is available on the prevalence of Cd in healthy swine in commercial operations. <P>The objectives of the present study are to: 1) determine the prevalence of Cd in different age groups of swine in a commercial operation; 2) determine the antibiotic resistance of swine isolates of Cd and compare them to resistance patterns of human isolates; and 3) compare the genetic relatedness of swine Cd isolates to human epidemic strain Cd isolates. If preliminary data indicates a high carriage rate of Cd in pre-harvest swine, the study will be modified and bacterial cultivation will be performed on carcasses in the processing plant.
Approach: Composite fecal samples (approximately 240 per month, representing 2,400 animals) will be collected for 10 months from breeding animals, piglets, growers, finishers, and pre-lagoon influent from 12 different geographical locations in an integrated swine operation in Texas. Four different geographical locations will be sampled on each of 3 different visits per month, so that all 12 locations are sampled once monthly. If the study is modified to include carcass swabs, 50 samples will be collected monthly from the processing plant. Samples will be cultured for Cd by bacteriologic methods; Cd isolates will be tested for toxin production (ELISA test) and for toxin genes (PCR); antibiotic resistance profiles will be determined on all swine Cd and compared to profiles of human isolates; swine isolates will be characterized for genetic make-up by pulsed-field gel electrophoresis (PFGE) and the PFGE banding patterns sent to the Centers for Disease Control and Prevention (CDC) for comparison to human Cd isolates in their data bank. CDC computer software will generate dendograms (genetic relatedness) for our data comparisons.