Prevention of enteric bacterial infections and modulation of gut microbiota with conjugated linoleic acids producing Lactobacillus in mice

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.

KEYWORDS:

• Probiotic
• conjugated linoleic acid
• enteric bacterial pathogen
• salmonellosis
• metagenomics
• intestinal microbiota

Acknowledgments

The authors would like to thank Dr. Vinod Nagarajan, Zabdiel Alvarado Martinez, Arpita Aditya, for their assistance during animal experiments. We also thank Dr. Rachel Dennis and Jasmine Mengers for their guide on histopathological studies.

Contributors

MP conceived the study, designed and carried out the experiments, analyzed the data, and wrote the manuscript. ZT contributed to in vivo experiments and manuscript draft. PP and CBe assisted in experimental preparation, sample processing, and microbiological experiments. CBi participated in reviewing and editing the manuscript. JM provided sequencing resources and helped in metagenomics. DB supervised the research and finalized the manuscript. All authors approved the final manuscript.

Ethics approval and consent to participate

Mice in vivo experiments were performed in ABSL2 facilities in Department of Animal and Avian Sciences, University of Maryland in accordant with protocol #R-NOV-17-55 approved by the Institutional Animal Care and Use Committee (IACUC). The best effort was made for minimizing the suffer of animals. To ensure animal welfare, mice were monitored and recorded for physical appearance and body weight on a daily basis during experimental period.

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Competing interests

The authors declare that they have no competing interests.

Additional information

Funding

This study was funded by Tier-1 (2945060) grants awarded to Debabrata Biswas.