Characterization of Probiotic Properties of a Novel Strain of Enterococcus Faecium

• Brooke Duke, Animal Science, University of Delaware

• Shafeekh Muyyarikkandy, Animal and Food Sciences, University of Delaware

Antimicrobial resistance (AMR) is an increasingly relevant crisis globally, contributing to nearly 5 million deaths annually. Due to overuse and improper use, antibiotics are becoming ineffective against many pathogens, which results in enhanced cost of treatments, longer recovery rates, and higher mortality rates. Furthermore, antibiotic alternatives are critical, and probiotics are one among the promising alternatives. Therefore, we aim to characterize a novel probiotic Enterococcus Faecium MLS15 isolated from a dairy source, including its antibacterial activities against pathogens such as E. coli and Salmonella Typhimurium. The probiotic strain MLS15 was genotypically characterized using the Comprehensive Genome Analysis Service via PATRIC on the BV-BRC platform. Various phenotypic assays were performed, some of which determined survivability in the gastrointestinal tract, such as acid tolerance, bile salt tolerance, lysozyme tolerance, gastric juice, and intestinal juice tolerance. Additional tests included auto-aggregation, co-aggregation with E. coli and Salmonella, cell surface hydrophobicity, hemolytic activity, and antibacterial activity. Genomic analysis revealed GC content of 34.78% with 24.74 Mb genomic length,1876 functional proteins without any AMR phenotypes. Additionally, thirteen secondary metabolite pathways were identified, among them limonene and pinene, which are notable natural antimicrobial agents. Phenotypically, the probiotic was resistant to bile salt and lysozyme (~8 log CFU/mL) even after 6 h of incubation. It showed an auto-aggregation of 8.13% and moderate hydrophobicity of 47.2%. Importantly, MLS15 did not exhibit hemolytic activity (γ), and showed promising antibacterial activity against S. Typhimurium (ATCC 14028 and 13311) and E. coli (ATCC 25922 and BAA 196), resulting in 100% mortality by 24 h. Furthermore, MLS15 showed antifungal activity during our preliminary screening. In conclusion, the isolated strain of E. faecium showed promising probiotic attributes both phenotypically and genotypically. However, further characterization, specifically of its antibacterial, antifungal, and in vivo potential, is necessary to assess its effectiveness as a promising probiotic for combating AMR.