Virulence genes and molecular characteristics of chicken-derived Escherichia coli

Abstract:

[Objective] The purpose of this test is to elucidate the pathogenicity and molecular epidemic characteristics of chicken-derived Escherichia coli, and to provide new ideas for exploring reasonable ways to prevent and control E. coli. [Methods] Livers of dead chicken samples were collected in Hebei Province from 2018 to 2019, and the isolated strains were systematically identified through selection of media selection, biochemical identification, and serum agglutination test. Detection of virulence genes in isolates was conducted by PCR. Cluster analysis of E. coli was performed with reference to phylogenetic classification. Multi-sequence typing analysis of housekeeping gene sequences with reference to 7 databases provided on the McMLST website database. [Results] The results show that 56 isolates conformed to the biochemical characteristics of E. coli were divided into 8 biochemical phenotypes. Among them, B4 (30.36%), B5 (25%), and B2 (23.21%) were the main biochemical phenotypes. 56 isolates of E. coli were positive for serum agglutination test, divided into 11 serotypes. O₇₈ (26.79%), O₂ (23.21%), O₁₅₇ (17.86%), and O₁ (14.29%) were the main epidemic serotypes. A total of 15 E. coli virulence genes were detected in 56 strains of E. coli, but no papC, ibeA, and ibeB genes were detected. The gene carrying rate of Adhesion-related gene fimC and antiserum survival factor-related gene ompA in all isolates is 100%. The detection rates of the genes of aatA, yijP, irp2, mat, and iss were 98.21%, 98.21%, 98.21%, 96.43% and 92.86%. The detection rates of iroN, fyuA, iucD and irp2 of E. coli and iron transport-related genes were all above 80%. Of the 56 strains of E. coli, 20 are Enterohemorrhagic E. coli (EHEC), followed by Enteroaggregative E. coli (EAEC) (n=4) and enterotoxigenic E. coli (ETEC) (n=2). These strains have more D group isolates, followed by B2 group. According to MLST typing analysis, there are 22 ST types in total, of which ST88, ST85 and ST243 are the main epidemic types. [Conclusion] The serotypes of E. coli were diverse and the virulence factors were various. The pathogenic E. coli also carried multiple virulence genes, indicating that animal-derived E. coli has a strong virulence basis.

Key words:Escherichia coli;virulence gene;MLST;phylogenetic group