摘要

       水产养殖环境中抗生素抗性细菌的出现是养殖鱼类疾病控制以及人类公共卫生的重大问题。接合移动遗传元件 (MGE) 参与了海洋细菌中抗生素抗性基因 (ARG) 的传播。在本研究中，我们首先设计了一个 PCR 靶向 traI 基因，该基因编码用于接合的必需松弛酶。通过这种新的 PCR，我们证明从沿海水产养殖场分离的 83 株菌株中有 5 株具有 traI 阳性 MGE。虽然属于 Shewanella sp. 的五个菌株之一。显示具有 SXT/R391 家族（ICEVchMex 样）的整合共轭元件，其他四种弧菌属的 MGE。显示具有与先前在 pAQU1 中描述的骨架结构相似的骨架结构。四种菌株中 pAQU1 样质粒共享的骨架结构对应于复制、分配和接合转移所需的约 100 kbp 高度保守区域，表明这些质粒构成了“pAQU 组”。显示 pAQU 组质粒能够将 tet(M) 和其他 ARG 从弧菌菌株接合转移到大肠杆菌中。将其中一种菌株中的pAQU组质粒命名为pAQU2，确定其完整核苷酸序列并与pAQU1进行比较。结果显示pAQU2比pAQU1含有更少的ARGs，并且这两个质粒中的大部分ARGs位于发现多个转座酶的相似区域，表明ARGs是通过几次DNA转座事件引入到祖先质粒中的其次是在水产养殖场进行药物选择。本研究的结果表明，“pAQU group”质粒可能在 ARGs 在海洋环境中的传播中发挥重要作用。

       Emergence of antibiotic-resistant bacteria in the aquaculture environment is a significant problem for disease control of cultured fish as well as in human public health. Conjugative mobile genetic elements (MGEs) are involved in dissemination of antibiotic resistance genes (ARGs) among marine bacteria. In the present study, we first designed a PCR targeting traI gene encoding essential relaxase for conjugation. By this new PCR, we demonstrated that five of 83 strains isolated from a coastal aquaculture site had traI-positive MGEs. While one of the five strains that belonged to Shewanella sp. was shown to have an integrative conjugative element of the SXT/R391 family (ICEVchMex-like), the MGEs of the other four strains of Vibrio spp. were shown to have the backbone structure similar to that of previously described in pAQU1. The backbone structure shared by the pAQU1-like plasmids in the four strains corresponded to a ~100-kbp highly conserved region required for replication, partition and conjugative transfer, suggesting that these plasmids constituted “pAQU group.” The pAQU group plasmids were shown to be capable of conjugative transfer of tet(M) and other ARGs from the Vibrio strains to E. coli. The pAQU group plasmid in one of the examined strains was designated as pAQU2, and its complete nucleotide sequence was determined and compared with that of pAQU1. The results revealed that pAQU2 contained fewer ARGs than pAQU1 did, and most of the ARGs in both of these plasmids were located in the similar region where multiple transposases were found, suggesting that the ARGs were introduced by several events of DNA transposition into an ancestral plasmid followed by drug selection in the aquaculture site. The results of the present study indicate that the “pAQU group” plasmids may play an important role in dissemination of ARGs in the marine environment.

https://www.frontiersin.org/articles/10.3389/fmicb.2014.00152/full