Evaluation of the control of pathogen load by an anti-Salmonella of cattle with persistent bacterium in a herd Salmonella infection

Objective—To determine whether an anti-Salmonella bacterium is involved in control of pathogen load in persistently infected cattle herds. Animals-24 Holstein calves experimentally infected and 39 Holstein cows naturally Infected with Salmonella spp. Procedures—An Escherichia coil (designated as F8E5) that possessed anti-Salmonella activity was isolated from Salmonella-negative bovine feces obtained from a herd with endemic Salmonella infection. In vitro analysis involved enumerating Salmonella enterica serovarTyphimurium coincubated with E coil P8E5. In vivo analysis involved coadministration of Salmonella spp and E coil P8E5 or an E col/control strain to neonatal Holstein calves. Fecal samples were collected on multiple days after inoculation, and quantitative PCR assay was performed by use of Salmonella-specific primers. Results—E coil P8E5 reduced viability of Salmonella spp in vitro. Shedding of Salmonella organisms was diminished in calves administered F co/i P8E5, whereas the control strain of E co/i had no effect on shedding of Salmonella organisms. Conclusions and Clinical Relevance—In this study, an E colt strain was identified that possessed bacteriocin-like activity and was able to decrease viability of Salmonella organisms in vitro and in vivo. Therefore, it is possible that this organism could be representative of native microbiota that dampen Salmonella spp in persistently infected cattle herds. (Am J Vet Res 2000;70:92-98)