Study indicates serotype, dose affect Salmonella shedding

Pigs inoculated with Salmonella organisms in a recent study shed the bacteria for various lengths of time, depending on the strain and dose given.

The scientific report “Salmonella fecal shedding and immune responses are dose- and serotype-dependent in pigs” was published in April (PloS One 2012;7:e34660). It notes that subclinical Salmonella infection and intermittent shedding increase the difficulty of detecting and controlling the bacteria in pigs. Improving our understanding of patterns and durations of fecal shedding of bacteria and host immune responses could improve screening for Salmonella infection and decrease the risk of human infections, the report states.

“To improve detection and control of Salmonella in live pigs, it is critical to better understand the duration and dynamics of intermittent Salmonella fecal shedding and immune response post exposure and during infection, together with the factors that affect these processes,” the report states.

Pigs challenged with high doses tended to start shedding Salmonella organisms more quickly and spend more time both continuously and intermittently shedding than did pigs given low doses. Those challenged with Salmonella Cubana and Salmonella Yoruba also had lengthier episodes of shedding than did those infected with the more-invasive Salmonella Typhimurium and Salmonella Derby, which are considered to be classic pig serotypes, although pigs challenged with the latter two Salmonella serotypes were more likely to temporarily stop shedding the bacteria and to stay infected for longer periods.

“Our results also indicated that compared to S. Yoruba and S. Cubana, pigs infected with S. Typhimurium and S. Derby are far more likely to enter the intermittent non-shedding state following the continuous or intermittent shedding states than to recover from these states,” the report states.

The report is available at www.plosone.org.