State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, 150069, China.
Institute of Microbiology and Epizootics, Centre for Infection Medicine, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany.
Vet Microbiol. 2021 Jun;257:109065. doi: 10.1016/j.vetmic.2021.109065. Epub 2021 Apr 9.
Tetracyclines are the broad-spectrum agents used in veterinary medicine and food animal production. Known mechanisms of tetracycline resistance include ribosome protection, active efflux and enzymatic inactivation. However, the presence of two different tet genes conferring different resistance mechanisms on the same plasmid has rarely been reported. In this study, we identified the tandem tetracycline resistance genes tet(61)-tet(58) on the novel plasmid pT4303. These tet genes were identified for the first time in Aerococcus urinaeequi. Reduced susceptibility to doxycycline was observed in S. aureus RN4220 harboring tet(61) when an extra tet(58) was expressed. Plasmid pT4303 was electrotransformed into S. aureus RN4220, E. faecalis JH2-2, S. suis BAA and E. coli DH5α and conferred tetracycline resistance (MIC ≥ 16) in both Gram-positive and Gram-negative bacteria, assuming that it might serve as a vehicle for the dissemination of the tetracycline resistance genes tet(61) and tet(58).
四环素类是兽医和食品动物生产中广泛使用的广谱药物。已知的四环素耐药机制包括核糖体保护、主动外排和酶失活。然而，同一质粒上同时存在两种不同的赋予不同耐药机制的四环素基因的情况很少有报道。在本研究中，我们在新型质粒 pT4303 上鉴定了串联的四环素耐药基因 tet(61)-tet(58)。这些 tet 基因是在尿肠球菌中首次发现的。当表达额外的 tet(58)时，携带 tet(61)的金黄色葡萄球菌 RN4220 对强力霉素的敏感性降低。质粒 pT4303 通过电转化进入金黄色葡萄球菌 RN4220、粪肠球菌 JH2-2、猪链球菌 BAA 和大肠杆菌 DH5α，并在革兰氏阳性和革兰氏阴性细菌中赋予四环素耐药性（MIC≥16），这表明它可能是四环素耐药基因 tet(61)和 tet(58)传播的载体。
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