Rizzotti Lucia, La Gioia Federica, Dellaglio Franco, Torriani Sandra
Dipartimento di Biotecnologie, Università degli Studi di Verona, Via della Pieve 70, San Floriano, Verona, Italy.
Antonie Van Leeuwenhoek. 2009 Jun;96(1):43-52. doi: 10.1007/s10482-009-9334-7. Epub 2009 Mar 31.
In the present study, 20 enterococci belonging to the species Enterococcus faecalis (12 strains), Enterococcus faecium (4), Enterococcus durans (2), Enterococcus hirae (1) and Enterococcus mundtii (1) and originating from a total production chain of swine meat commodities were analysed to investigate the diversity of their tetracycline resistance gene tet(M). PCR-RFLP and sequence analysis showed that the tet(M) gene of most strains can be correlated with the Tn916 transposon. Conversely, tet(M) of six E. faecalis and the E. hirae strain, all isolated from pig faecal samples, may be associated with previously undescribed members of the Tn916-1545 transposon family. In vitro filter conjugation trials showed the ability of 50% of the enterococcal strains, including E. mundtii, to transfer the tet(M) gene (and the associated Tn916 and new transposons) to E. faecalis or Listeria innocua recipient strains. tet(M) gene transfer to L. innocua recipient was also directly observed in meat food products. Collectively, these sequence and conjugation data indicate that various transposons can be responsible of the spread of tetracycline resistance in enterococci and validate the opinion that Enterococcus species are important sources of antibiotic resistance genes for potentially pathogenic bacteria occurring in the food chain.
在本研究中，对来自猪肉制品整个生产链的20株肠球菌进行了分析，这些肠球菌分别属于粪肠球菌（12株）、屎肠球菌（4株）、耐久肠球菌（2株）、海氏肠球菌（1株）和蒙氏肠球菌（1株），以调查其四环素抗性基因tet(M)的多样性。PCR-RFLP和序列分析表明，大多数菌株的tet(M)基因可与Tn916转座子相关。相反，从猪粪便样本中分离出的6株粪肠球菌和海氏肠球菌菌株的tet(M)，可能与Tn916-1545转座子家族中以前未描述的成员有关。体外滤膜接合试验表明，包括蒙氏肠球菌在内的50%的肠球菌菌株能够将tet(M)基因（以及相关的Tn91和新的转座子）转移到粪肠球菌或无害李斯特菌受体菌株中。在肉类食品中也直接观察到tet(M)基因转移到无害李斯特菌受体中。总的来说，这些序列和接合数据表明，各种转座子可能是肠球菌中四环素抗性传播的原因，并证实了肠球菌是食物链中潜在致病细菌抗生素抗性基因重要来源的观点。
