摘要
      虽然对抗生素耐药性质粒的最详细分析集中在临床分离株中发现的那些，但对流动遗传元件的巨大环境库及其编码的耐药性和毒力因子知之甚少。我们从受废水影响的沿海湿地中选择性分离出三株耐头孢噻肟大肠杆菌。头孢噻肟耐药表型在一小时后可传播给实验室大肠杆菌菌株，每个受体的频率高达10−3个转偶联物。其中两个质粒也将头孢噻肟耐药性转移到了恶臭假单胞菌，但这些质粒无法将这种耐药性从恶臭假单胞杆菌反向转移到大肠杆菌。除了头孢菌素外，大肠杆菌跨偶联物还遗传了对至少七类不同抗生素的耐药性。完整的核苷酸序列显示具有全球分布的复制子序列类型F31:A4:B1和F18:B1:C4的大型IncF型质粒携带不同的抗生素耐药性和毒力基因。质粒编码超广谱β-内酰胺酶blaCTX-M-15或blaCTX-M-55，每个都与插入序列ISEc9相关，尽管在不同的局部排列中。尽管抗性谱相似，但质粒只有一个共同的抗性基因，氨基糖苷乙酰转移酶aac（3）-IIe。质粒附属货物还包括参与铁获取和防御宿主免疫的毒力因子。尽管它们的序列相似，但还是检测到了一些大规模重组事件，包括重排和反转。总之，用单一抗生素头孢噻肟进行筛选，产生了具有多重耐药性和毒力因子的偶联质粒。显然，限制抗生素耐药性和毒力在细菌中传播的努力必须包括更好地了解自然和人类影响环境中的流动元素。
Abstract
While most detailed analyses of antibiotic resistance plasmids focus on those found in clinical isolates, less is known about the vast environmental reservoir of mobile genetic elements and the resistance and virulence factors they encode. We selectively isolated three strains of cefotaxime-resistant Escherichia coli from a wastewater-impacted coastal wetland. The cefotaxime-resistant phenotype was transmissible to a lab strain of E. coli after one hour, with frequencies as high as 10−3 transconjugants per recipient. Two of the plasmids also transferred cefotaxime resistance to Pseudomonas putida, but these were unable to back-transfer this resistance from P. putida to E. coli. In addition to the cephalosporins, E. coli transconjugants inherited resistance to at least seven distinct classes of antibiotics. Complete nucleotide sequences revealed large IncF-type plasmids with globally distributed replicon sequence types F31:A4:B1 and F18:B1:C4 carrying diverse antibiotic resistance and virulence genes. The plasmids encoded extended-spectrum β-lactamases blaCTX-M-15 or blaCTX-M-55, each associated with the insertion sequence ISEc9, although in different local arrangements. Despite similar resistance profiles, the plasmids shared only one resistance gene in common, the aminoglycoside acetyltransferase aac(3)-IIe. Plasmid accessory cargo also included virulence factors involved in iron acquisition and defense against host immunity. Despite their sequence similarities, several large-scale recombination events were detected, including rearrangements and inversions. In conclusion, selection with a single antibiotic, cefotaxime, yielded conjugative plasmids conferring multiple resistance and virulence factors. Clearly, efforts to limit the spread of antibiotic resistance and virulence among bacteria must include a greater understanding of mobile elements in the natural and human-impacted environments.

https://www.sciencedirect.com/science/article/abs/pii/S0147619X23000136