Molecular Epidemiology of Extraintestinal Pathogenic Escherichia coli Causing Hemorrhagic Pneumonia in Mink in Northern China

Abstract

The molecular epidemiology and biological characteristics of <i>Escherichia coli</i> associated with hemorrhagic pneumonia (HP) mink from five Chinese Provinces were determined. From 2017 to 2019, 85 <i>E. coli</i> strains were identified from 115 lung samples of mink suffering from HP. These samples were subjected to serotyping, antimicrobial susceptibility, detection of virulence genes, phylogenetic grouping, whole-genome sequencing, drug resistant gene, multilocus sequence typing (MLST) and biofilm-forming assays. <i>E. coli</i> strains were divided into 18 serotypes. Thirty-nine <i>E. coli</i> strains belonged to the O11 serotype. Eighty-five <i>E. coli</i> strains were classified into seven phylogenetic groups: E (45.9%, 39/85), A (27.1%, 23/85), B1 (14.1%, 12/85), B2 (3.7%, 3/85), D (3.7%, 3/85), F (2.4%, 2/85) and clade I (1.2%, 1/85). MLST showed that the main sequence types (STs) were ST457 (27/66), All <i>E. coli</i> strains had ≥4 virulence genes. The prevalence of virulence was 98.8% for <i>yijp</i> and <i>fimC</i>, 96.5% for <i>iucD</i>, 95.3% for <i>ompA</i>, 91.8% for <i>cnf-Ⅰ</i>, 89.4% for <i>mat</i>, 82.3% for <i>hlyF</i>, and 81.2% for <i>ibeB.</i> The prevalence of virulence genes <i>iss</i>, <i>cva/cvi</i>, <i>aatA</i>, <i>ibeA</i>, <i>vat</i>, <i>hlyF</i>, and <i>STa</i> was 3.5-57.6%. All <i>E. coli</i> strains were sensitive to sulfamethoxazole, but high resistance was shown to tetracycline (76.5%), chloramphenicol (71.8%), ciprofloxacin (63.5%) and florfenicol (52.9%), resistance to other antibiotics was 35.3-16.5%. The types and ratios of drug-resistance genes were <i>tet(A), strA, strB, sul2, oqxA, blaTEM-1B, floR, and catA1</i> had the highest frequency from 34%-65%, which were consistent with our drug resistance phenotype tetracycline, florfenicol, quinolones, chloramphenicol, the <i>bla-NDM-I</i> and <i>mcr-I</i> were presented in ST457 strains. Out of 85 <i>E. coli</i> strains, six (7.1%) possessed a strong ability, 12 (14.1%) possessed a moderate ability, and 64 (75.3%) showed a weak ability to form biofilm. Our data will aid understanding of the epidemiological background and provide a clinical basis for HP treatment in mink caused by <i>E. coli</i>.