Submitted to: Anaerobe
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2009
Publication Date: 9/22/2009
Citation: Norman, K.N., Harvey, R.B., Scott, M.H., Hume, M.E., Andrews, K., Brawley, A.D. 2009. Varied prevalence of Clostridium difficile in an integrated swine operation. Anaerobe. 15:256-260.
Interpretive Summary: Since 2003, there have been frequent outbreaks of hospital-associated infections by a new strain of the bacterium Clostridium difficile (Cd). This organism has been responsible for death and disease in thousands of humans in North America. Although the origin of this new strain is unknown, some in the medical community theorize that it could have come from pigs and may be a food-associated disease from pork. In our study, we sampled 1008 pigs for Cd and found that although 131 were positive for Cd, it was predominantly in young pigs and not market-age ones. Furthermore, the Cd strain did not appear to be the same as the human epidemic strain. These findings are of major economic importance to the swine industry in that they suggest pork is probably not a factor in transmission of this human disease.
Technical Abstract: The objective of this study was to compare the prevalence of Clostridium difficile among different age and production groups of swine in a vertically integrated swine operation in Texas in 2006 and to compare our isolates to other animal and human isolates. Preliminary results are based on 131 C. difficile isolates arising from 1008 swine fecal samples and pork trim samples (overall prevalence of 13%). The prevalence (number positive/number tested in production type) of C. difficile was different between the groups (P less than 0.001), and was highest among farrowing barn inhabitants (predominantly piglets, but also included lactating sows and influent) at 36.5% (95/260), followed by 8.2% (10/122) for nursery, 6.5% (4/61) for pork products, 3.9% (15/382) for grower-finisher, and 3.8% (7/182) for breeding boars and sows. Of the 131 isolates, 119 were positive by PCR for both the toxin A (tcdA) and toxin B (tcdB) genes. All 131 isolates harbored the tcdC gene deletion and 130 of the isolates were positive for the cdtB binary toxin, typical of hyper-virulent toxin producing strains. All 131 isolates were resistant to cefoxitin, ciprofloxacin, and imipenem, whereas all were sensitive to metronidazole, piperacillin/tazobactam, amoxicillin/clavulanic acid, and vancomycin. The majority of isolates were resistant to clindamycin; resistant or intermediate to ampicillin; and sensitive to tetracycline and chloramphenicol. There was an increased (P less than 0.001) number of isolates for the timeframe of Sept.-Feb. compared to Mar.-Aug. C. difficile most commonly originated among farrowing barn-production types (primarily piglets) and not in grower/finisher production. Relatively low prevalence in late production suggests a low food safety risk; however, the isolates in our study may be considered more virulent because of the binary toxin and tcdC gene deletion, and similar isolates have been linked to outbreaks of C. difficile in hospitals of North America and Europe.