Mitigating Virulence of Environmental Enterococcus faecalis Via Fermented Food-Derived Lactic Acid Bacteria.

Abstract

Enterococcus faecalis, a Gram-positive bacterium commonly found in environmental reservoirs, poses growing concerns due to its adaptability, virulence traits, and emerging resistance to critical antibiotics. In this study, eight Enterococcus strains (JUSS 01-03, 05-07, 09, and 10) were isolated from irrigation water contaminated with sewage around Bengaluru, India. All isolates were subjected for antibiotic susceptibility testing, where, JUSS 05 (E. faecalis) and JUSS 06 (E. faecalis) exhibited ampicillin resistance (1.5 and 2.5 mm zones), suggesting the isolates to be antibiotic-resistant with high virulence. This virulent activity is further supported by cell surface hydrophobicity and auto-aggregation showing the highest hydrophobicity and aggregation, respectively. JUSS 06 and JUSS 05 exhibited the strongest biofilm formation (~ 0.65 OD), linking hydrophobicity to biofilm biomass. Probiotic interventions isolated from fermented food, using Pediococcus acidilactici (JUFF, JUFB) and Streptococcus thermophilus (JUBM) significantly reduced virulence traits across isolates. JUBM had the greatest impact on reducing hydrophobicity, aggregation, and biofilm, likely via exopolysaccharide production and surface interference. JUFF demonstrated consistent and broad-spectrum anti-biofilm activity against JUSS 05, JUSS 06, and the clinical strain CV2656 (P < 0.0001). The reduction of hydrophobicity and aggregation by lactic acid bacteria (LAB) indicates disruption of early biofilm development stages and interference with adhesion mechanisms. These findings emphasize the pathogenic potential of environmental E. faecalis and highlight the effectiveness of food-derived LAB in reducing virulence factors. Probiotic applications could serve as sustainable bio-interventions against environmental isolates of enterococcal species, further investigation is needed to evaluate their application potential.