Isolation, Identification, and in Vitro Safety Evaluation of Enterococcus faecalis in the Stool of Healthy Infants
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Abstract:
To screen for safe strains of Enterococcus faecalis, stool samples were collected from healthy 1-month-old infants and strains were cultured in MRS medium. A total of 64 E. faecalis strains were identified via 16S rRNA sequencing. Among them, 16 were selected for in vitro safety evaluation, and their hemolytic property, antibiotic sensitivity, and six virulence genes were determined. Based on the hemolysis results, the 16 strains of E. faecalis did not exhibit β-hemolysis. Further, the antibiotic sensitivity tests revealed that the strains were highly resistant to tetracycline (56.25%) and erythromycin (43.75%), followed by penicillin (37.50%) and ciprofloxacin (31.25%). No vancomycin- and teicoplanin-resistant strains were found. Eight relatively safe strains were identified based on the above experiments, and five virulence genes: ace, asal, efaA, cylA, and gelE, were subsequently determined, with ace+ efaA+ gelE+ as the dominant mode. Finally, four candidate strains of E. faecalis, namely LX29, LX31, LX41, and LX50, were acquired after comprehensive evaluation. Overall, our findings lay the foundation for subsequent functional research and product development.
