Investigation and research on pathogenic Escherichia coli from wild animals in the Qinghai-Xizang Plateau in 2023

Objective To investigate the prevalence of pathogenic E. coli carried by wild animals in the Qinghai-Xizang Plateau. Fecal samples were collected from wild blue sheep, white-lipped deer, and red deer from Qinghai province, as well as from a variety of bird faeces including the Himalayan vulture, red-billed chough, rock pigeon, and ruddy shelduck.

Methods A total of 237 faecal samples of wild animals and birds collected in Qinghai province in 2023 were subjected to selective isolation and cultivation of E. coli using the E. coli broth enrichment method followed by CHROMagarTM E. coli Coliform Chromogenic Medium. The virulence genes of the isolates were detected through polymerase chain reaction. Furthermore, representative isolates were subjected to whole-genome sequencing and E. coli pathotype characterization.

Results There were 169 strains in total were isolated from the feces of wild animals and birds in the Qinghai-Xizang Plateau, including E. coli (n=60), Pantoea spp. (n=26), Pseudomonas spp. (n=23), Serratia spp. (n=16), and Enterobacter spp. (n=12). Based on the virulence genes carried by E. coli, 46 strains were classified as different pathovars, with 33 strains being hybrid pathovars carrying multiple virulence genes, accounting for 55.00%, with the most common pathovar hybrids being a combination of two pathovars (38.33%). Through phylogenetic analysis, among the 60 strains of E. coli, the predominant phylogroup belonged to B1 group (42/60), followed other phylogroups are A (5 strains), D (5 strains), B2 (4 strains), E (3 strains), and C (1 strain). All strains carried the gene fim, with over half of the strains carrying extraintestinal pathogenic E. coli-related virulence genes, with positive rates of genes kpsD, aslA, and hlyA being 28.33%, 26.67%, and 26.67%, respectively, and positive rates of astA and stx (stx1, stx2) genes both being 23.33%. Three strains were positive for eae, with a low positivity rate (5.00%).

Conclusion Pathogenic E. coli is widely present in wild animals such as blue sheep, white-lipped deer, red deer, and wild birds in the Qinghai-Xizang Plateau. Plateau wild animals are reservoir hosts for pathogenic E. coli, facilitating the discovery of various pathogenic types and phylogroup strains, thereby providing bacterial resources and scientific evidence for understanding the pathogenicity and epidemiological patterns of E. coli.