Background Probiotics decrease the risk of necrotizing enterocolits (NEC). We sought to determine the impact of Bifidobacterium longum subsp. infantis (B. infantis) in the established rat model of NEC. Methods Rat pups delivered one day prior to term gestation were assigned to one of three groups: dam-fed (DF), formula-fed (FF), or fed with formula supplemented with 5 × 106 CFU B. infantis per day (FF+Binf). Experimental pups were exposed to hypoxia and cold stress. Ileal tissue was examined for pathology and expression of inflammatory mediators, antimicrobial peptides, and goblet-cell products. Ceca were assessed for bacterial composition by analysis of 16S rRNA sequence. Results Administration of B. infantis significantly reduced the incidence of NEC, decreased expression of Il6, Cxcl1, Tnfa, Il23, and iNOS, and decreased expression of the antimicrobial peptides Reg3b and Reg3g. There was significant microbial heterogeneity both within groups and between experiments. The cecal microbiota was not significantly different between the FF and FF+Binf groups. Bifidobacteria were not detected in the cecum in significant numbers. Conclusions In the rat model, the inflammation associated with NEC was attenuated by administration of probiotic B. infantis. Dysbiosis was highly variable precluding determination of the precise role of the microbiota in experimental NEC.

The skin functions as more than a physical barrier to infection. Epithelial cells of the skin can synthesize antimicrobial peptides, including defensins, which exhibit direct antimicrobial activity. Here we characterize the expression pattern, genetic variation and activity of the major β-defensin expressed in canine skin, canine β-defensin 103 (CBD103). The gene encoding CBD103 exhibits two forms of polymorphism: a common 3-basepair deletion allele and a gene copy-number variation. Golden retrievers and Labrador retrievers were the only breeds that encoded the variant allele of CBD103, termed CBD103ΔG23. Both these breeds also exhibited a CBD103 gene copy-number polymorphism that ranged from 2 to 4 gene-copies per diploid genome. Recombinant CBD103 and CBD103ΔG23, as well as the human ortholog human β-defensin 3 (hBD3) and hBD3ΔG23, showed potent and comparable antimicrobial killing against both methicillin-susceptible and methicillin-resistant Staphylococcus pseudintermedius. Skin biopsy specimens from dogs with atopic dermatitis revealed CBD103 expression levels similar to those in healthy controls and comparable at lesional and nonlesional sites. This expression pattern in dogs differs from the previously reported reduced expression of the human ortholog in atopic dermatitis. Overall, the similarities of CBD103 and its human ortholog reported here support the notion that the domestic dog may serve as a valuable model for studying β-defensin biology in the skin.

The mammalian intestine harbors a vast, complex and dynamic microbial population, which has profound effects on host nutrition, intestinal function and immune response, as well as influence on physiology outside of the alimentary tract. Imbalance in the composition of the dense colonizing bacterial population can increase susceptibility to various acute and chronic diseases. Valuable insights on the association of the microbiota with disease critically depend on investigation of mouse models. Like in humans, the microbial community in the mouse intestine is relatively stable and resilient, yet can be influenced by environmental factors. An often-overlooked variable in research is basic animal husbandry, which can potentially alter mouse physiology and experimental outcomes. This study examined the effects of common husbandry practices, including food and bedding alterations, as well as facility and cage changes, on the gut microbiota over a short time course of five days using three culture-independent techniques, quantitative PCR, terminal restriction fragment length polymorphism (TRFLP) and next generation sequencing (NGS). This study detected a substantial transient alteration in microbiota after the common practice of a short cross-campus facility transfer, but found no comparable alterations in microbiota within 5 days of switches in common laboratory food or bedding, or following an isolated cage change in mice acclimated to their housing facility. Our results highlight the importance of an acclimation period following even simple transfer of mice between campus facilities, and highlights that occult changes in microbiota should be considered when imposing husbandry variables on laboratory animals.

Necrotizing enterocolitis (NEC) is a devastating disease of premature infants. Probiotics decrease the risk of NEC in clinical and experimental studies. Antimicrobial peptides protect the gut against noxious microbes and shape the commensal microbiota, but their role in NEC remains unclear. We report that like in human ontogeny, the rat pup has low expression of Paneth cell antimicrobials, which increases rapidly during normal development. To investigate the expression of antimicrobial peptides in experimental NEC and the impact of probiotics on their expression, premature rats were divided into three groups: dam fed (DF), hand fed with formula (FF), or hand fed with formula containing Bifidobacterium bifidum (FF+BIF). All groups were exposed to asphyxia and cold stress. The expression of lysozyme, secretory phospholipase A2, pancreatic-associated proteins 1 and 3 mRNA was elevated in the FF (NEC) group, compared to the DF and FF+BIF groups where disease was attenuated. We conclude that induction of antimicrobial peptides occurs in experimental NEC similar to that reported in human disease and is attenuated when disease is averted by probiotic B. bifidum. The induction of antimicrobial peptides is likely an adaptive mucosal response that is often not sufficient to prevent disease in the premature gut.

Burkholderia pseudomallei, a causative agent of melioidosis, is a facultative intracellular Gram-negative bacterium that can survive and multiply inside the macrophages. Toll-like receptors are one class of pattern recognition receptors (PRRs) that have been documented to play significant role in B. pseudomallei infection. In the present study, we investigated a potential role of nucleotide-binding oligomerization domain-containing protein 1 and 2 (NOD1 and NOD2), cytoplasmic pattern recognition receptors, in B. pseudomallei-infected mouse macrophage cell line RAW 264.7. Both live and heat-killed B. pseudomallei were able to up-regulate NOD1 and NOD2 expression in a time-dependent manner. Marked reduction of a negative regulator, suppressor of cytokine signaling 3 (SOCS3), expression was observed only in B. pseudomallei-infected NOD2-depleted macrophages and not in NOD1-depleted macrophages. The decrease in SOCS3 expression also led to an increase in IFN-γ responsiveness as judged by an enhanced STAT-1 phosphorylation on tyrosine 701 in the B. pseudomallei-infected macrophages. Together, these results suggested that, in addition to using other PRRs to evade macrophage defense, B. pseudomallei may also use NOD2 to regulate a negative regulator like SOCS3.