Abstract
Probiotics and prebiotics are promising strategies to counteract Salmonella prevalence in swine. In the present study, we investigated the effects of prebiotics (fructo- (FOS), galacto- (GOS) and mannan- (MOS) oligosaccharides) and the bacteriocinogenic Bifidobacterium thermophilum RBL67 (RBL67) on Salmonella enterica subsp. enterica serovar Typhimurium N-15 (N-15) colonization using the PolyFermS in vitro continuous fermentation model simulating the swine proximal colon. The PolyFermS model was designed with a first-stage reactor containing immobilized fecal pig microbiota. This reactor continuously inoculated five parallel second-stage reactors, a control and four treatment reactors, all operated with proximal colon conditions. FOS and GOS (5.2g/day), and MOS (half dosage) and RBL67 (108 copy numbers/mL applied daily) were tested on the ability of N-15 to colonize reactors, inoculated with the same microbiota. Reactor effluents were collected daily and analyzed for microbial composition (quantitative PCR and 454 pyrosequencing of 16S rRNA gene pool) and main metabolites (HPLC). RBL67 and N-15 were shown to stably colonize the system. Colonization of N-15 was strongly inhibited by FOS and GOS, whereas addition of RBL67 alone or combined with MOS showed intermediate results. However, the effect of FOS and GOS was enhanced when prebiotics were combined with a daily addition of RBL67. FOS and GOS increased the total short chain fatty acid production, especially acetate and propionate. RBL67 combined with FOS additionally stimulated butyrate production. Our study demonstrates the suitability of the porcine PolyFermS in vitro model to study nutritional effects of pro- and prebiotics on gut microbiota composition and activity. It can further be used to monitor Salmonella colonization. The inhibition effects of FOS and GOS on N-15 colonization are partly due to an increased acetate production, while further antimicrobial mechanisms may contribute to an enhanced inhibition with prebiotic-RBL67 combinations. A future direction of this work could be to understand the anti-Salmonella effects of Bifidobacterium thermophilum RBL67 in the presence of prebiotics to unravel the mechanism of this probiotic:pathogen interaction.
Highlights
Probiotics and prebiotics are promising strategies to counteract Salmonella prevalence in swine
Our study demonstrates the suitability of the porcine PolyFermS in vitro model to study nutritional effects of pro- and prebiotics on gut microbiota composition and activity
The inhibition effects of FOS and GOS on N-15 colonization are partly due to an increased acetate production, while further antimicrobial mechanisms may contribute to an enhanced inhibition with prebiotic-Bifidobacterium thermophilum RBL67 (RBL67) combinations
Summary
Probiotics and prebiotics are promising strategies to counteract Salmonella prevalence in swine. Salmonella are highly prevalent in swine where they affect about one third of all production holdings in the European Union [1]. Since antibiotics for growth promotion have been banned, alternative strategies to improve gut health are necessary to maintain productivity. Gut microbial composition and activity can be directly influenced via the diet [2]. This in turn impacts the colonization ability of enteric pathogens, such as Salmonella, through competitive exclusion mechanisms [3]. Probiotics and prebiotics, known for their potential to modulate gut microbial composition and activity, are amongst the promising alternative strategies [4]
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