Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2008
Publication Date: 1/5/2009
Citation: Patton, T.G., Sharma, V.K., Carlson, S.A. 2009. Evaluation of the Control of Pathogen Load by an Anti-Salmonella Bacterium in a Herd of Cattle with Persistent Salmonella Infection. American Journal of Veterinary Research. 70(1):92-98. Interpretive Summary: Background: Salmonella is a common food contaminant and can cause severe health problems in humans. Salmonella is found in most animals and can be distributed through the feces. Although, Salmonella does not always cause illness to its host, it has been observed to cause disease in some cattle herds. Furthermore, not all of the cows in the herd become ill and do not harbor Salmonella. One possible explanation for this phenomenon is that there are other bacteria native to the cow that prevents the Salmonella from permanently occupying the cow. Description: An E. coli was isolated from feces of a cow that has never tested positive for Salmonella, despite living with cows that have tested positive for Salmonella. This E. coli decreased the growth of Salmonella in the laboratory and in calves. This E. coli also inhibited the growth of other bacteria when grown together in the laboratory. Impact: We have identified a bacterium that is capable of decreasing Salmonella from being excreted in the feces. This could impact food safety since fecal contamination has become a major issue. By decreasing harmful bacteria at the source without the use of antibiotics can reduce the problem of fecal contamination and antibiotic resistance.
Technical Abstract: Objective: To isolate an anti-Salmonella bacterium that may control pathogen load in persistently-infected cattle herds. Animals: 24 Holstein calves. Procedures: An Escherchia coli (designated as P8E5) that possesses anti-Salmonella activity was isolated from Salmonella negative bovine feces obtained from an endemic Salmonella herd. In vitro analysis involved co-incubating P8E5 and Salmonella enterica serotype Typhimurium (S. Typhimurium), followed by bacterial enumeration. In vivo analysis involved neonatal Holstein calves that were co-administered Salmonella and either P8E5 or an E. coli control strain. Fecal samples were collected on multiple days post-infection and quantitative PCR was performed using Salmonella-specific primers. Results: P8E5 reduced Salmonella viability in vitro. Shedding was diminished in the calves exposed to P8E5 whereas control strains had no effect. Conclusions and Clinical Relevance: The E. coli identified in this study possessed bacteriocin-like activity that was able to decrease Salmonella viability in vitro and in vivo. It is therefore possible that this organism could be representative of native microbiota that dampens Salmonella in cattle herds persistently infected with this pathogen.