Reduction of Virulence and Antibiotic Resistance of Salmonella in Commercial Broiler Ceca Samples

Introduction: Livestock may serve as a reservoir for antibiotic resistant bacteria that may transfer to our food system; some of zoonotic concern such as Salmonella. These antibiotic resistant bacteria result in a reduced effectiveness of antibiotic compounds in treating illness. Interventions are needed to reduce the reservoir of antibiotic resistance genes in food animals.

Purpose: The purpose of this study was to evaluate XPC supplementation as a method to reduce virulence and antimicrobial resistance of Salmonella in broilers.

Methods: A large field study was conducted to determine the effects of feeding XPC on reducing Salmonella in broilers, including an evaluation of Salmonella virulence and antibiotic resistance to florfenicol, ceftiofur, and enrofloxacin, in a total of 134 commercial broiler houses. In this study, houses were fed either a diet that contained 1.25 kg/MT of Original XPC (XPC) or the company standard diet (CON). At the processing plant, one cecum was collected from between 50-100 birds/house (4,675 total cecum tested). Data were analyzed in SAS using the Chi-Square procedure with feeding treatment as the main effect.

Results: All isolated Salmonella colonies were measured for virulence and antibiotic resistance. Virulence was significantly lowered (P<0.0001) in isolates from XPC fed birds compared to CON (0.17% vs. 1.05%, respectively). Salmonella antibiotic resistance was significantly lowered (P<0.0001) in isolates from XPC fed birds compared to CON (florfenicol: 1.95% vs. 12.84%; ceftiofur: 0.48% vs. 9.55%; enrofloxacin: 0.01% vs. 3.96%, respectively).

Significance: These data suggest that virulence and antibiotic resistance of Salmonella can be reduced by the inclusion of XPC in broiler diets.