Department of Mathematics, Information, and Computer Sciences, Point Loma Nazarene University, 3900 Lomaland Dr., San Diego, CA 92106, United States of America.
Department of Biology, Point Loma Nazarene University, 3900 Lomaland Dr., San Diego, CA 92106, United States of America.
Plasmid. 2023 May;126:102682. doi: 10.1016/j.plasmid.2023.102682. Epub 2023 Apr 4.
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 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 bla or bla, 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.
虽然大多数对抗生素耐药质粒的详细分析都集中在临床分离株中发现的那些，但对环境中移动遗传元件的巨大储存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地分离出三株头孢噻肟耐药大肠杆菌。头孢噻肟耐药表型在 1 小时后可传递给实验室大肠杆菌菌株，受体的转化率高达 10 个转导体。两个质粒还将头孢噻肟耐药性转移给了铜绿假单胞菌，但这些质粒无法将这种耐药性从铜绿假单胞菌反向转移到大肠杆菌。除了头孢菌素外，大肠杆菌转导体还继承了至少七种不同类别的抗生素的耐药性。完整的核苷酸序列揭示了大型 IncF 型质粒，具有全球分布的复制子序列类型 F31:A4:B1 和 F18:B1:C4，携带多种抗生素耐药性和毒力基因。质粒编码了扩展谱β-内酰胺酶 bla 或 bla，每个都与插入序列 ISEc9 相关联，尽管在不同的局部排列中。尽管耐药谱相似，但这些质粒仅共享一个共同的耐药基因，即氨基糖苷乙酰转移酶 aac(3)-IIe。质粒附加货物还包括与铁摄取和抵御宿主免疫有关的毒力因子。尽管它们具有序列相似性，但检测到了几个大规模的重组事件，包括重排和反转。总之，用单一抗生素头孢噻肟进行选择，产生了赋予多种耐药性和毒力因子的可接合质粒。显然，限制抗生素耐药性和毒力在细菌中的传播的努力必须包括对自然和人为影响环境中的移动元件有更深入的了解。
