Isolation and characterization of potential probiotic Enterococcus faecalis strains from healthy lambs' feces

As global animal husbandry begins to reduce the use of antibiotics, finding safe and effective alternatives to antibiotics has become the key to ensuring the healthy and sustainable development of the industry. Probiotics are regarded as one of the most potential alternative strategies because of their functions of regulating intestinal microecological balance and inhibiting pathogenic bacteria.

This study was performed to determine the potential probiotic Enterococcus faecalis strains from the feces of healthy lambs.

One hundred and fifty-one rectal swabs were collected. BHI (brain heart infusion) medium was used to isolate target E. faecalis strains, and 16 S rRNA was used to identify the type of bacteria. The potential probiotic strain (L118) with high acid resistance and negative for hemolytic and gelatinase activitys was selected and its characteristics including amino acid decarboxylase activity, virulence and antibiotic resistance, bacterial adhesion to solvents, aggregation capability and cellulase and amylase activitys were determined. In addition, animal feeding experiments were conducted about the candidate bacteria in goats.

A non-hemolytic and gelatinase-negative strain (L118), with a high survival rate in simulated gastric fluid (pH 3.0) and simulated intestinal fluid, was screened from 151 strains of E. faecalis. At the same time, arginine decarboxylase activity and susceptibility to antibiotics such as penicillin, amikacin, vancomycin were observed. Also, L118 displayed high hydrophobicity, low auto-aggregation ability, and strong co-aggregation capacity with pathogenic bacteria (Salmonella typhimurium, Staphylococcus aureus). It also has cellulase and amylase activities. Meanwhile, E. faecalis L118 increased the red blood cells and hemoglobin content in the blood, serum glutathione peroxidase activity and intestinal lactobacillus (P < 0.05).

An E. faecalis strain with high acid resistance was confirmed to possess safety and probiotic properties and provides an application and development of a new feed probiotic additive.