Determining the Efficacy of a Dairy-Origin Probiotic, Propionibacterium freudenreichii subspecies freudenreichii, against Multidrug-Resistant Salmonella Heidelberg in Turkeys

Abstract

Poultry contributes to more than half of foodborne salmonellosis in the U.S. through contaminated meat, eggs, and other products. Recently, Salmonella Heidelberg (SH) has emerged as a major serovar transmitted to humans via poultry. Cecal colonization of SH and consequent fecal shedding of the pathogen contaminate the environment and carcasses, necessitating interventions to control SH in poultry. Efficacy of a dairy-originated non-host specific probiotic bacterium, Propionibacterium freudenreichii subsp. freudenreichii NRRL 3523 (PF), against a multidrug-resistant (MDR) SH in turkeys has been narrated in this thesis. In vitro experiments revealed that PF reduced the virulence factors of SH associated with its colonization in the host (P<0.05). In addition, PF exhibited anti-SH qualities such as growth reduction, adhesion to intestinal epithelial cells, and survival to low pH and bile salts without possessing pathogenic characters (hemolysis, invasion into the epithelial cells and antibiotic resistance) (P>0.05). Further, the efficacy of PF against SH colonization and its dissemination to internal organs such as liver and spleen in turkeys were validated using in vivo experiments in 2-, 7-, and 12-week-old commercial turkeys. A high PF viability in turkey cecum (3.5-5.0 log10 CFU/ml) was observed in different age group turkeys after supplementing 1010 CFU/ml through drinking water. The PF supplementation resulted in 1.6 to 2.2-, 1.0 to 1.3-, and 1.7- to 2.6- log10 CFU/g reduction of SH in the cecum of turkeys at 2-, 7- and 12-week, respectively (P<0.05), compared to the controls. A reduced dissemination of SH to liver and spleen (P<0.05) also resulted. Populations of PF increased the relative abundance of several production-associated beneficial bacteria, including carbohydrate fermenting and short chain fatty acid producing groups (P<0.05). However, SH inoculation caused an increase in abundance of microflora associated with inflammatory response (P<0.05). Overall the results revealed that PF could be used in turkeys to control MDR SH colonization in the cecum and its invasion of liver and spleen without adversely affecting the cecal microbiome. Whereas SH challenge resulted in an abundance of inflammation associated bacteria, and the condition was effectively alleviated by increased abundance of other beneficial bacteria as a result of PF supplementation.