摘要
出身背景
气单胞菌是广泛分布于生态系统中的机会性病原体。已知它们能够获得抗生素抗性基因，包括编码抗最后一种抗生素的蛋白质的基因，如tmexCD toprJ、mcr和碳青霉烯酶基因。我们研究了从人类、动物和水样中，特别是从中国医院废水中采集的tmexCD toprJ阳性气单胞菌的基因组和表型特征。
方法
从活体动物、肉类、水和人类身上采集样本。在选择性培养基中分离这些样品中的气单胞菌菌株。采用肉汤微量稀释法检测了所有气单胞菌的耐药性。通过聚合酶链式反应（PCR）证实了tmexD-toprJ的存在。对所有tmexCD toprJ阳性（n=36）和选定的tmexCD toprJ阴性（n=18）气单胞菌菌株进行全基因组测序。通过生物信息学分析确定了抗微生物基因的携带、tmexD-toprJ的遗传环境以及tmexD-toprJ阳性气单胞菌的遗传多样性。利用Harvest Suite建立了气单胞菌的系统发育树。
调查结果
在从不同来源分离的636株气单胞菌中，36株对tmexD-toprJ呈阳性，其中鱼类中tmexD-toprJ的患病率最高（8.8%，95%CI%3.6–17.2%），其次是医院废水（6.5%，95%CI%4.3–9.3%），河水（2.0%，0.1-10.9）和鸭子（1.2%，95%CI%，3.6-17.2%）。所有tmexCD toprJ阳性气单胞菌都携带多种抗微生物耐药性基因，并对不同种类的抗生素表现出耐药性。在21株菌株中鉴定出tmexD-toprJ、mcr和blaKPC-2共存。tmexCD toprJ阳性气单胞菌菌株具有遗传多样性，属于四个不同的物种，可分为三个主要谱系。tmexD-toprJ基因簇主要位于气单胞菌属的染色体（35/36）上，只有一株菌株携带质粒携带的tmexD-toprJ簇。tmexCD toprJ基因与七种不同类型的遗传环境有关，每种遗传环境都携带不同类型的可移动元件，这些元件可能负责介导该基因簇的传播。
Abstract
Background
Aeromonas species are opportunistic pathogens distributed widely in the ecosystem. They are known to be capable of acquiring antibiotic resistance genes, including those encoding proteins against last-line antibiotics, such as the tmexCD-toprJ, mcr and carbapenemase genes. We investigated the genomic and phenotypic characteristics of tmexCD-toprJ-positive Aeromonas strains collected from human, animals, and water samples, particularly those from hospital wastewater in China.

Methods
Samples were collected from living animals, meat, water and human. Aeromonas strains in these samples were isolated in selective media. Antimicrobial resistance profiles of all Aeromonas strains were tested by the broth microdilution method. The presence of tmexCD-toprJ was verified by polymerase chain reaction (PCR). All tmexCD-toprJ-positive (n = 36) and selected tmexCD-toprJ-negative (n = 18) Aeromonas strains were subjected to whole genome sequencing. Carriage of antimicrobial resistance genes, the genetic environment of tmexCD-toprJ and genetic diversity of tmexCD-toprJ-positive Aeromonas strains were determined by bioinformatics analysis. Phylogenetic tree of the Aeromonas strains was built by using the Harvest Suite.

Findings
Among the 636 Aeromonas strains isolated from different sources, 36 were positive for tmexCD-toprJ, with the highest prevalence of tmexCD-toprJ being found in fishes (8.8%, 95 CI% 3.6–17.2%), followed by hospital wastewater (6.5%, 95 CI% 4.3–9.3%), river water (2.0%, 0.1–10.9) and duck (1.2%, 95 CI% 3.6–17.2%). All tmexCD-toprJ-positive Aeromonas strains carried multiple antimicrobial resistance genes and exhibited resistance to different classes of antibiotics. Co-existence of tmexCD-toprJ, mcr and blaKPC-2 were identified in 21 strains. The tmexCD-toprJ-positive Aeromonas strains were genetically diverse and found to belong to four different species that could be clustered into three major lineages. The tmexCD-toprJ gene clusters were predominantly located in the chromosome (35/36) of Aeromonas spp., with only one strain carrying the plasmid-borne tmexCD-toprJ cluster. The tmexCD-toprJ genes were associated with seven different types of genetic environments, each of which carried distinct types of mobile elements that may be responsible for mediating transmission of this gene cluster.

https://www.sciencedirect.com/science/article/abs/pii/S1368764623000080