Scholarlink

<p><i>Escherichia coli</i> strains are naturally susceptible to polymyxins. The frequency of polymyxin resistance in <i>E. coli</i> associated with chromosomal mutations is usually low (0.2–0.6%). Here, we report polymyxin-resistant <i>E. coli</i> strains isolated from flies (Diptera: Muscomorpha) and animals (bovine, equine, canine, and sheep) cohabitants on two dairy farms, A and B (Botucatu, State of Sao Paulo, Brazil), in 2015. We isolated 877 <i>E. coli</i> from the external surface of flies and healthy animal feces. The screening of polymyxin-resistant <i>E. coli</i> was performed using MacConkey agar with polymyxin B (2&#xa0;µg/mL). We detected a high percentage of polymyxin-resistant isolates from flies (33.33%; 66/198) and farm animals (46.09%; 313/679). Fisher’s exact test revealed no associations between polymyxin resistant and multidrug resistant strains. We investigated <i>mcr</i> genes (<i>mcr-1</i>, <i>mcr-2</i>, <i>mcr-3</i>, <i>mcr-4</i>, and <i>mcr-5</i>) using PCR, and five <i>E. coli</i> from calves (farm B) present the <i>mcr-1</i> gene. Sanger sequencing and conjugation assays were performed for gene confirmation. All five <i>mcr-1</i>-positive <i>E. coli</i> showed fingerprints more than 80% similar assayed by pulsed-field gel electrophoresis. The minimum inhibitory concentrations (MICs) for polymyxin B against <i>mcr-1</i>-positive <i>E. coli</i> were 4&#xa0;µg/mL (two strains), and 8&#xa0;µg/mL (three strains). Whole-genome sequencing showed <i>mcr-1.1</i> gene in the IncX4 plasmid and a class 1 integron unusual harboring <i>sul3</i> and <i>qacL</i> as a non-variable structure. In Brazil, the therapeutic use of polymyxin is allowed, but stewardship in dairy cattle is uncommon; thus, our data indicate a probable selection of polymyxin-resistant strains related to environmental pressure.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

High frequency of chromosomal polymyxin resistance in Escherichia coli isolated from dairy farm animals and genomic analysis of mcr-1-positive strain

  • 期刊论文

  • 发表日期：

    2025年2月18日

查看全文
  • Taila dos Santos Alves,
  • Vinícius Sanches Rosa,
  • Gustavo Henrique Batista Lara,
  • Márcio Garcia Ribeiro,
  • Domingos da Silva Leite

摘要

Escherichia coli strains are naturally susceptible to polymyxins. The frequency of polymyxin resistance in E. coli associated with chromosomal mutations is usually low (0.2–0.6%). Here, we report polymyxin-resistant E. coli strains isolated from flies (Diptera: Muscomorpha) and animals (bovine, equine, canine, and sheep) cohabitants on two dairy farms, A and B (Botucatu, State of Sao Paulo, Brazil), in 2015. We isolated 877 E. coli from the external surface of flies and healthy animal feces. The screening of polymyxin-resistant E. coli was performed using MacConkey agar with polymyxin B (2 µg/mL). We detected a high percentage of polymyxin-resistant isolates from flies (33.33%; 66/198) and farm animals (46.09%; 313/679). Fisher’s exact test revealed no associations between polymyxin resistant and multidrug resistant strains. We investigated mcr genes (mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5) using PCR, and five E. coli from calves (farm B) present the mcr-1 gene. Sanger sequencing and conjugation assays were performed for gene confirmation. All five mcr-1-positive E. coli showed fingerprints more than 80% similar assayed by pulsed-field gel electrophoresis. The minimum inhibitory concentrations (MICs) for polymyxin B against mcr-1-positive E. coli were 4 µg/mL (two strains), and 8 µg/mL (three strains). Whole-genome sequencing showed mcr-1.1 gene in the IncX4 plasmid and a class 1 integron unusual harboring sul3 and qacL as a non-variable structure. In Brazil, the therapeutic use of polymyxin is allowed, but stewardship in dairy cattle is uncommon; thus, our data indicate a probable selection of polymyxin-resistant strains related to environmental pressure.