Safety assessment of Enterococcus lactis strains complemented with comparative genomics analysis reveals probiotic and safety characteristics of the entire species

Abstract

Background The gut microbiota is considered a rich source for potential novel probiotics. Enterococcus genus is a normal component of a healthy gut microbiota, suggesting its vital role. Nosocomial infections caused mainly by E. facalis and E. faecium have been attributed to the plasticity of the Enterococcus genomes. In this study, we assessed the probiotic and safety characteristics of two E. lactis strains isolated from the human gut microbiota using in-vitro and in silico approaches. Additionally, the safety of the E. lactis species was evaluated using comparative genomics analysis. Results The two E. lactis strains 10NA and 50NA showed resistance to bile salts and acid tolerance with antibacterial activity against Escherichia coli, Salmonella typhi, and Clostridioides difficile. For safety assays, the two strains did not display any type of hemolysis on blood agar, and the survival of Caco-2 cells was not significantly different (P-value > 0.05) compared to the control using cell free supernatants at 100% (v/v), 50% (v/v), 10% (v/v), and 5% (v/v) concentrations. Regarding antibiotic susceptibility, both strains were sensitive to vancomycin, tetracycline, and chloramphenicol. Comprehensive whole-genome analysis revealed no concerning associations between virulence or antibiotic resistance genes and any of the identified mobile genetic elements. Comparative genome analysis with closely related E. faecium species genomes revealed the distinctive genomic safety of the E. lactis species. Conclusions Our two E. lactis strains showed promising probiotic properties in-vitro. Their genomes were devoid of any transferable antibiotic resistance genes. In silico comparative analysis confirmed the safety of the E. lactis species. These results suggest that E. lactis species could be a potential source for safer Enterococcus probiotic supplements.

Unraveling the antimicrobial potential of Lactiplantibacillus plantarum strains TE0907 and TE1809 sourced from Bufo gargarizans: advancing the frontier of probiotic-based therapeutics

“…Subsequent to meeting the prerequisite of intestinal epithelial adherence, the endeavor progresses toward identifying strains with antimicrobial properties, wherein the assessment of LAB's antibacterial activity typically involves utilizing corresponding pathogenic bacteria as indicator organisms to determine the strains' effectiveness. Our selection was based on the antimicrobial capacity of the isolates against E. coli, S. aureus , and C. jejuni, etc ., which have been linked to numerous foodborne outbreaks (Gray and Killinger, 1966 ; Lowy, 1998 ; Kerr and Snelling, 2009 ; Gomes et al, 2016 ; Dar et al, 2017 ), with criteria emphasizing isolates that exhibited a zone of inhibition surpassing that of a control strain, specifically a commercially recognized strain known for producing antimicrobial metabolites (Ahmed et al, 2023 ). Our goal was to find new potential antimicrobial metabolites-producing strains and ones that could have a more significant potential than cells already reported, when compared to the L. plantarum DY1 as reported by Mao et al ( 2020 ), our strains not only exhibit enhanced antibacterial activity but also potentially possess a broader spectrum of microbial inhibition.…”