Abstract
ABSTRACT Probiotics are recognized for outcompeting pathogenic bacteria by competitive receptor-mediated colonization and secretion of functional metabolites which are antimicrobial against certain microbes as well as improving host’s gut health and immunity. Recently, we have constructed a bioactive Lactobacillus casei (LC) strain, LC+mcra , by inserting mcra (myosin cross-reactive antigen) gene, which stimulates the conversion of conjugated linoleic acids. In this study, we evaluated the modulation of gut microbiome and protective roles of LC+mcra against pathogenic Salmonella enterica serovar Typhimurium (ST) and enterohemorrhagic E. coli (EHEC) infections in BALB/cJ mice. We observed that LC+mcra colonized efficiently in mice gut intestine and competitively reduced the infection with ST and EHEC in various locations of small and large intestine, specifically cecum, jejunum, and ileum (p < 0.05). Positive modulation of the cecal microbiota, for example, higher relative abundances of Firmicutes, lower relative abundances of Proteobacteria, and increased bacterial species diversity/richness, was detected in ST-challenged mice pretreated with LC+mcra based on 16S metagenomic sequencing. Cytokine gene expression analysis indicated that mice pretreated with LC+mcra associated with attenuated bacterial pathogen-induced gut inflammation. Furthermore, mice fed daily with LC+mcra for one week could protect themselves from the impairments caused by enteric infections with ST or EHEC. These impairments include weight loss, negative hematological changes, intestinal histological alterations, and potential death. This in vivo study suggests that daily consumption of novel conjugated linoleic acids over-producing probiotic effectively improves intestinal microbiota composition and prevents/combats foodborne enteric bacterial infections with pathogenic Salmonella and diarrheagenic E. coli.
Highlights
The majority of human gut epithelial surfaces are colonized and safeguarded by a tremendous number of microorganisms including bacteria, viruses, fungi and protozoans which are known as common gut microflora; each of them is crucial in forming and balancing a complex ecosystem with microbial diversity [1]
Human distal gastrointestinal (GI) tract can house more than 1000 distinct bacterial species, and the total number was estimated to be larger than 1014 CFU/gm of fecal material
We aimed to evaluate the protective roles of Lactobacillus casei (LC)+mcra on modulating/recovering gut intestinal microflora composition and combating/alleviating foodborne enteric bacterial pathogenic infections in vivo based on mice model
Summary
The majority of human gut epithelial surfaces are colonized and safeguarded by a tremendous number of microorganisms including bacteria, viruses, fungi and protozoans which are known as common gut microflora; each of them is crucial in forming and balancing a complex ecosystem with microbial diversity [1]. These large number of microorganisms build up a microbial genetic repertoire approximately 100 times greater than that of the human host. As a consequence of imbalanced gut microflora, opportunistic pathogens, their produced metabolites, proteins, and/or toxins can take over the gut ecosystem and negatively impact host gut health
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