Z-009. Molecular Analysis and Diversity of Clostridium difficile among Swine Herds in the Midwest

A. Baker, E. Davis, T. Rehberger;
Agtech Products Inc., Waukesha, WI.

Enteric clostridial infections in swine occur predominantly in the neonatal period and Clostridium difficile is a common cause of scours. This study assessed the prevalence, diversity, and toxinotypes of C. difficile present among neonatal pigs showing clinical signs of clostridial disease within swine operations throughout the Midwest. A total of 180 swabs were collected from regional swine farms containing less than 2500 sows at 16 sites across the Midwest. An additional 333 swabs were collected at 11 sites within a Midwest integrated commercial swine company containing approximately 150,000 sows for comparison of clostridial diversity. Samples were plated on selective media for isolation of C. difficile. Isolated colonies were picked, DNA was extracted, and multiplex PCR confirmed the presence of tcdA (Toxin A) and tcdB (Toxin B). There were 102 isolates confirmed as toxigenic from 27.2% of the pigs swabbed from the regional farm sites and 476 isolates from 57.6% of the pigs from the commercial farm sites. Isolates were genetically typed using RAPD PCR and dendrograms were constructed to assess diversity among the isolates. Fifty one unique clusters were identified from the 102 regional farm isolates and 126 clusters were created from the 476 commercial farm isolates. A subset of strains representing a majority of the diversity encompassed in both the regional and commercial farm dendrograms were toxinotyped based upon the restriction enzyme digestion patterns of HincII, AccI, and EcoRI. Of the 45 isolates typed, 44 were Toxinotype V which has been commonly isolated from pigs and the remaining unique isolate was Toxinotype I. All the isolates in that cluster had identical RAPD banding patterns and were isolated from the same regional site. The results of this study indicated that C. difficile is prevalent in the swine industry, and the diversity shown among isolates from the regional and integrated farms was comparable. Analysis of the dendrograms revealed that there were both shared and unique strains among all the sites studied, and intervention strategies used to control disease outbreaks must account for the diversity of this pathogen.