健康婴儿粪便中粪肠球菌的分离鉴定与体外安全性评价

Isolation, Identification, and in Vitro Safety Evaluation of Enterococcus faecalis in the Stool of Healthy Infants

摘要:

为筛选出符合安全要求的粪肠球菌，该研究以采集的1月龄健康婴儿粪便样本为研究对象，采用MRS分离纯化和16S rRNA测序进行菌种鉴定，共鉴定出64株粪肠球菌。该研究对其中16株菌进行体外安全性评价，分别考察其溶血性、抗生素敏感性和6种毒力基因。结果发现16株粪肠球菌均未出现β溶血现象；药敏试验发现菌株对四环素（56.25%）、红霉素（43.75%）耐药率较高，青霉素（37.50%）和环丙沙星（31.25%）次之，未发现万古霉素和替考拉宁耐受菌株；继上述实验获得的8 株相对安全菌株进行毒力基因检测，共检出5种毒力基因：ace、asal、efaA、cylA、gelE，以ace＋efaA＋gelE＋为主要携带模式；综合评价后最终得到4株粪肠球菌候选菌株，编号为：LX29、LX31、LX41、LX50，可为后续的功能性研究和产品开发奠定基础。

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.