Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy.
Environ Microbiol Rep. 2014 Apr;6(2):184-90. doi: 10.1111/1758-2229.12125. Epub 2013 Nov 25.
To gain insights into the relationships and the genetic exchange among environmental and clinical enterococci, 59 strains (29 from marine aquaculture sites and 30 from clinical settings) resistant to tetracycline, erythromycin, ampicillin and/or gentamicin were analysed for the antibiotic resistance tet(M), tet(L), tet(O), erm(A), erm(B), mef blaZ, aac(6')-Ie aph(2″)-Ia and virulence gelE, cylB, efaA and esp genes, and for the copper resistance gene tcrB. Antibiotic resistance and virulence genes were detected more frequently in clinical than in environmental enterococci; the opposite was true for copper resistance. Conjugation experiments demonstrated the transfer of antibiotic resistance genes from marine to clinical enterococci in interspecific mating and the uncommon joint transfer of tet(L) and erm(B). Enterobacterial repetitive intergenic consensus polymerase chain reaction typing evidenced a cluster (90% similarity) encompassing strains carrying multiple antibiotic resistance genes from both sets; the others marine isolates exhibited polyclonality and bore tcrB. Our results demonstrate that antibiotic-resistant marine enterococci bear antibiotic resistance genes transferable to humans and suggest that copper resistance, not observed among clinical strains, may be useful for survival in the environment, whereas virulence genes likely confer no advantage to enterococcal populations adapted to a lifestyle outside the host.
为了深入了解环境和临床肠球菌之间的关系和遗传交换，我们分析了 59 株（29 株来自海洋水产养殖场所，30 株来自临床环境）对四环素、红霉素、氨苄西林和/或庆大霉素耐药的肠球菌。这些菌株被检测了抗生素耐药基因 tet(M)、tet(L)、tet(O)、erm(A)、erm(B)、mef blaZ、aac(6')-Ie aph(2″)-Ia 和 virulence gelE、cylB、efaA 和 esp，以及铜耐药基因 tcrB。临床肠球菌中抗生素耐药和毒力基因的检出率高于环境肠球菌；而铜耐药基因则相反。接合实验表明，在种间交配中，海洋肠球菌可以向临床肠球菌转移抗生素耐药基因，而 tet(L)和 erm(B)的共同转移则比较少见。肠杆菌重复基因间共有 consensus 聚合酶链反应（Enterobacterial repetitive intergenic consensus polymerase chain reaction，ERIC-PCR）分型表明，一个包含携带两种来源的多种抗生素耐药基因的菌株的聚类（相似度为 90%）；其他海洋分离株则表现出多克隆性，并携带 tcrB。我们的结果表明，抗生素耐药的海洋肠球菌携带可转移给人类的抗生素耐药基因，并表明在临床菌株中未观察到的铜耐药性可能有助于其在环境中的生存，而毒力基因可能对适应宿主外生活方式的肠球菌种群没有优势。
