Choi Jong-Mi, Woo Gun-Jo
Laboratory of Food Safety and Evaluation, Department of Food Bioscience and Technology, Korea University, Anam-dong 5-ga, Seongbuk-Gu, Seoul, 136-713, Korea.
Curr Microbiol. 2015 Apr;70(4):476-84. doi: 10.1007/s00284-014-0742-1. Epub 2014 Dec 7.
Enterococcus faecalis has the ability to conjugate with the aid of aggregation substance (AS) and inducible sex pheromones to exchange genetic elements in food matrix. To evaluate the food safety condition and the transferable factor, 250 tetracycline-resistant food-borne E. faecalis were collected in Korea. Among the isolates, a majority of tetracycline-resistant isolates (49.6 %) harbored both the tet(M) and tet(L) genes together, followed by tet(M) (19.6 %), and tet(L) (6.8 %) alone. Also, we found the combination of tet(L)/tet(M)/tet(O) or tet(M)/tet(O). We identified two tet(S) genes including the isolate carrying tet(M) + tet(S) genes. Additionally, most E. faecalis were positive for cpd and ccf (both 96.8 %) followed by cob (57.2 %). Through mating experiments, we confirmed E. faecalis possessing the Int-Tn gene and/or any AS gene successfully transferred tet genes to JH2-2 E. faecalis, whereas neither E. faecalis carrying AS genes nor the Int-Tn gene showed the conjugation. Pulsed-field gel electrophoresis results supported a distinct pattern, implying transfer of genetic information. Our study revealed a high occurrence of tetracycline resistance genes in E. faecalis from various foods. The widespread dissemination of tetracycline resistance genes would be promoted to transfer tetracycline resistance genes by pheromone-mediated conjugation systems.
粪肠球菌能够借助聚集物质（AS）和可诱导性信息素进行接合，从而在食物基质中交换遗传元件。为评估食品安全状况和可转移因子，在韩国收集了250株耐四环素的食源性粪肠球菌。在这些分离株中，大多数耐四环素分离株（49.6%）同时携带tet(M)和tet(L)基因，其次是单独携带tet(M)的分离株（19.6%）和单独携带tet(L)的分离株（6.8%）。此外，我们还发现了tet(L)/tet(M)/tet(O)或tet(M)/tet(O)的组合。我们鉴定出两个tet(S)基因，包括携带tet(M)+tet(S)基因的分离株。另外，大多数粪肠球菌cpd和ccf检测呈阳性（均为96.8%），其次是cob（57.2%）。通过接合实验，我们证实携带Int-Tn基因和/或任何AS基因的粪肠球菌成功地将tet基因转移到了JH2-2粪肠球菌中，而携带AS基因或Int-Tn基因的粪肠球菌均未发生接合。脉冲场凝胶电泳结果支持了一种独特的模式，暗示了遗传信息的转移。我们的研究表明，来自各种食物的粪肠球菌中四环素抗性基因的发生率很高。四环素抗性基因的广泛传播将通过信息素介导的接合系统促进四环素抗性基因的转移。
