| This research addressed for the first time the prevalence of Clostridium difficile in a veal calf production unit and in feedlot beef cattle using a longitudinal design.;For the second study, four commercial feedlots in Alberta, Canada were enrolled. Fecal samples were collected at the time of arrival and shipping. Selective culture for C. difficile was performed, and isolates were characterized by ribotyping and pulsed-field gel electrophoresis. A total of 543 cattle were enrolled. Clostridium difficile was isolated from 3.3% of cattle at the time of arrival and from 5.5% at the time of shipping. Overall, there was no difference in the prevalence of C. difficile shedding, however, on one of the farms, prevalence was higher at shipping. When only paired samples were evaluated, there was a significant difference in prevalence between arrival and exit in one of the four feedlots, as well as overall, with C. difficile isolated from 2.1% at arrival and 5.5% at exit. All the isolates recovered were ribotype 078, a toxinotype V strain with genes encoding toxins A, B and CDT. In addition, all strains were classified as NAP7 by PFGE.;For the veal farm study, rectal swabs were collected from 183 calves at arrival, as well as 1, 17 and 21 weeks later. Selective culture for C. difficile was performed and the isolates recovered were characterized by PCR ribotyping, PCR for tcdA, tcdB, cdtA and tet(M) and E-test for tetracycline susceptibility. Overall, C. difficile was isolated from 32% (56/174), 51% (88/172), 2% (4/183) and 2% (4/156) calves during successive samplings. Calves were two times more likely to test positive during the second sampling compared to the first sampling. The number of calves shedding C. difficile was significantly lower after second sampling. Twelve different ribotypes were present at the first time point, and only three ribotypes at the second sampling. Ribotype 078 was the most common strain found. Close to 99% of the toxigenic strains isolated in the study have been identified in humans. There was a significant increase in tetracycline resistant isolates and in the number of bacteria carrying the tet(M) gene. |
