Sublethal concentrations of antibiotics enhance transmission of antibiotic resistance genes in environmental Escherichia coli

作者：Charlotte J. Gray-Hammerton, Steven P. Hooton, Kirsty Sands, Timothy R. Walsh, Claudia Orbegozo Rubio, Edward Portal, Chris Hudson, Dov J. Stekel, Christine E. R. Dodd, Jon L. Hobman · 发表于：Frontiers in Microbiology · 年份：2025 · DOI：10.3389/fmicb.2025.1675089 · 被引用次数：3 · 研究领域：Antibiotic Resistance in Bacteria、Pharmaceutical and Antibiotic Environmental Impacts、Bacteriophages and microbial interactions

Third-generation cephalosporin-resistant Enterobacterales are ranked second on the World Health Organisation (WHO)’s Bacterial Priority Pathogens List. Amongst them, extended-spectrum β-lactamase-producing Escherichia coli (ESBL-Ec) are used by the WHO as sentinel organisms to monitor the spread of antibiotic resistance worldwide and are often associated with mobilisable multidrug resistance (MDR). However, we know less about how ESBL-producing genes spread in environmental E. coli . This study investigates how the bla CTX-M-15 gene from ESBL-Ec isolated on a UK dairy farm could transfer between strains. For this study, 39 E. coli were isolated from a single dairy farm over 4 months, using cefotaxime-supplemented selective media. All had similar antibiotic susceptibility test phenotypes, and PCR, whole genome sequencing (WGS), and resistance gene transmission experiments demonstrated they were all closely related. In silico multi-locus sequence typing and single-nucleotide polymorphism analysis showed that all 39 strains were Sequence Type 2325, but plasmid carriage differed. In total, 35 of the 39 ESBL-Ec strains were multidrug resistant, displaying bla CTX-M type cephalosporin resistance and resistance to fluoroquinolones and tetracyclines. WGS confirmed all 39 isolates carried the IS Ecp1 mobile genetic element carrying the bla CTX-M-15 ESBL-producing gene, and the qnrS1 partial quinolone resistance gene in the chromosome. A total of 35 strains also carried tetAR within th...