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Simple Summary: Salmonella typhimurium is one of the most widespread enteric pathogens causing enterocolitis in warm-blooded animals worldwide. It is frequently spread within pig production and threatens not only primary hosts but consumers of pork meat as well. Overall, finding novel non-antibiotic agents is desirable in preventing salmonellosis outbreaks or reducing ongoing illness, where multi-strain probiotics are promising adepts. We tested a multi-strain bacterial mixture in the gnotobiotic piglet model to verify potential probiotic and anti-Salmonella properties in vivo. The bacterial consortium colonized the gut successfully and protected piglet hosts against Salmonella translocation to the blood system. Thus, the assembled bacterial mix has a promising potential for probiotic intervention in pig production management. Probiotics are a potential strategy for salmonellosis control. A defined pig microbiota (DPM) mixture of nine bacterial strains previously exhibited probiotic and anti-Salmonella properties in vitro. Therefore, we evaluated its gut colonization ability and protection effect against S. typhimurium LT2-induced infection in the gnotobiotic piglet model. The DPM mixture successfully colonized the piglet gut and was stable and safe until the end of the experiment. The colon was inhabited by about 9 log CFU g−1 with a significant representation of bifidobacteria and lactobacilli compared to ileal levels around 7–8 log CFU g−1. Spore-forming clostridia and bacilli seemed to inhabit the environment only temporarily. The bacterial consortium contributed to the colonization of the gut at an entire length. The amplicon profile analysis supported the cultivation trend with a considerable representation of lactobacilli with bacilli in the ileum and bifidobacteria with clostridia in the colon. Although there was no significant Salmonella-positive elimination, it seems that the administered bacteria conferred the protection of infected piglets because of the slowed delayed infection manifestation without translocations of Salmonella cells to the blood circulation. Due to its colonization stability and potential protective anti-Salmonella traits, the DPM mixture has promising potential in pig production applications. However, advanced immunological tests are needed. [ABSTRACT FROM AUTHOR]

This article is an editorial discussing the use of pigs as a translational animal model in immunological research. Pigs are often used in biomedical research due to their similarity to humans in anatomy, physiology, and genetics. The article highlights various aspects of pig immunology, including the role of microbiota, the importance of colostrum and breast milk, the toll-like receptor 4 pathway, and the impact of specific microbes on the host. The authors emphasize the need for further development and characterization of pig models in biomedical research. [Extracted from the article]

Gnotobiotic (GN) animals with simple and defined microbiota can help to elucidate host-pathogen interferences. Hysterectomy-derived germ-free (GF) minipigs were associated at 4 and 24 h post-hysterectomy with porcine commensal mucinolytic Bifidobacterium boum RP36 (RP36) strain or non-mucinolytic strain RP37 (RP37) or at 4 h post-hysterectomy with Lactobacillus amylovorus (LA). One-week-old GN minipigs were infected with Salmonella Typhimurium LT2 strain (LT2). We monitored histological changes in the ileum, mRNA expression of Toll-like receptors (TLRs) 2, 4, and 9 and their related molecules lipopolysaccharide-binding protein (LBP), coreceptors MD-2 and CD14, adaptor proteins MyD88 and TRIF, and receptor for advanced glycation end products (RAGE) in the ileum and colon. LT2 significantly induced expression of TLR2, TLR4, MyD88, LBP, MD-2, and CD14 in the ileum and TLR4, MyD88, TRIF, LBP, and CD14 in the colon. The LT2 infection also significantly increased plasmatic levels of inflammatory markers interleukin (IL)-6 and IL-12/23p40. The previous colonization with RP37 alleviated damage of the ileum caused by the Salmonella infection, and RP37 and LA downregulated plasmatic levels of IL-6. A defined oligo-microbiota composed of bacterial species with selected properties should probably be more effective in downregulating inflammatory response than single bacteria. [ABSTRACT FROM AUTHOR]

The beneficial effect of probiotic Escherichia coli strain Nissle 1917 (EcN) suggests the gut epithelium plays a basic role in immune interactions with bacteria. Contrary to other commensal strains of Escherichia coli, EcN profoundly modulates the gut barrier to elevate its resistance to microbial pathogens. The present review documents the properties of EcN that have led to the protection of gnotobiotic pigs against lethal enteric infections. This effect could be important in light of the growing number of acquired deficiencies that paralyze gut immunity in humans. doi: 10.1111/j.1753-4887.2010.00305.x

The gut constitutes a prominent part of the immune system. Its commensal microflora plays an important role in defense and in tolerance to diet allergens. Disturbances in immune regulations may lead to food allergy. Among commensal bacteria, bifidobactefia are able to induce mechanisms of immune tolerance. Comprehension of their mutual cross-talk with the host is necessary for understanding their role in the diet and in food supplements.

Probiotics are a potential strategy for salmonellosis control. A defined pig microbiota (DPM) mixture of nine bacterial strains previously exhibited probiotic and anti- Salmonella properties in vitro. Therefore, we evaluated its gut colonization ability and protection effect against S. typhimurium LT2-induced infection in the gnotobiotic piglet model. The DPM mixture successfully colonized the piglet gut and was stable and safe until the end of the experiment. The colon was inhabited by about 9 log CFU g -1 with a significant representation of bifidobacteria and lactobacilli compared to ileal levels around 7-8 log CFU g -1 . Spore-forming clostridia and bacilli seemed to inhabit the environment only temporarily. The bacterial consortium contributed to the colonization of the gut at an entire length. The amplicon profile analysis supported the cultivation trend with a considerable representation of lactobacilli with bacilli in the ileum and bifidobacteria with clostridia in the colon. Although there was no significant Salmonella -positive elimination, it seems that the administered bacteria conferred the protection of infected piglets because of the slowed delayed infection manifestation without translocations of Salmonella cells to the blood circulation. Due to its colonization stability and potential protective anti- Salmonella traits, the DPM mixture has promising potential in pig production applications. However, advanced immunological tests are needed.

Salmonella Typhimurium is a Gram-negative bacterium that causes enterocolitis in humans and pigs. Lipopolysaccharide (LPS) is a component of the outer leaflet of Gram-negative bacteria that provokes endotoxin shock. LPS can be synthesized completely or incompletely and creates S (smooth) or R (rough) chemotypes. Toll-like receptors (TLR) 2, 4, and 9 initiate an inflammatory reaction to combat bacterial infections. We associated/challenged one-week-old gnotobiotic piglets with wild-type S. Typhimurium with S chemotype or its isogenic ∆ rfa mutants with R chemotype LPS. The wild-type S. Typhimurium induced TLR2 and TLR4 mRNA expression but not TLR9 mRNA expression in the ileum and colon of one-week-old gnotobiotic piglets 24 h after challenge. The TLR2 and TLR4 stimulatory effects of the S. Typhimurium ∆ rfa mutants were related to the completeness of their LPS chain. The transcription of IL-12/23 p40, IFN-γ, and IL-6 in the intestine and the intestinal and plasmatic levels of IL-12/23 p40 and IL-6 but not IFN-γ were related to the activation of TLR2 and TLR4 signaling pathways. The avirulent S . Typhimurium ∆ rfa mutants are potentially useful for modulation of the TLR2 and TLR4 signaling pathways to protect the immunocompromised gnotobiotic piglets against subsequent infection with the virulent S. Typhimurium.