Longitudinal investigation of Clostridium difficile shedding in piglets.

A longitudinal study of Clostridium difficile colonization in piglets was performed on a conventional swine farm in Ontario, Canada. Fecal samples were collected from 10 sows prior to their expected farrowing date, and then from all their piglets on days 2, 7, 30, 44 and 62 of life. C. difficile was isolated from 4/10 (40%) of sows prior to farrowing, 90/121 (74%) piglets on day 2, 66/117 (56%) on day 7, 45/113 (40%) on day 30, 23/101 (23%) on day 44 and 2/54 (3.7%) on day 62. There was a significant decrease in colonization over time (P < 0.0001). Overall, C. difficile was isolated from one or more samples from 116/121 (96%) piglets. There was an inverse association between sow colonization and piglet colonization on day 2 (P < 0.0001) and a positive association on day 7 (P = 0.001). Ribotype 078/toxinotype V predominated, accounting for 213/234 (91%) isolates. A toxinotype XIV strain that has been previously found in humans in the province was the 2nd most common, but was mainly found in sows, not piglets. Overall, 227/234 (97%) of isolates were from types that have been isolated from humans in the province. Intermittent colonization was detected in 11 (9.6%) piglets. The decline in C. difficile colonization over the first 2 months of life was remarkable. The variation in colonization over a relatively short period of time has important implications for the design and interpretation of studies evaluating C. difficile colonization in pigs, since relatively small differences in age may have a major confounding effect on the prevalence of colonization. The decline in prevalence over time may also have implications on public health concerns, since colonization rates of animals at the time of slaughter are presumably more relevant than those earlier in life.