Genetic Diversity, Host Adaptation, and Public Health Implications of Escherichia coli in Qinghai Plateau Animals

Abstract Background Escherichia coli is an important pathogen that causes diarrhea in humans and animals. In this study, we performed MLST typing, phylogenetic grouping, antimicrobial resistance phenotype, antibiotics resistance genes, and virulence genes of E. coli isolated from yaks and wild animals in the Qinghai Plateau in China. Methods We tested 88 and 36 E. coli strains from yaks and wild animals for antimicrobial susceptibility test, antibiotics resistance genes, virulence genes, phylogenetic groups and multi-locus sequence typing. Results Phylogenetic analysis revealed that the isolates were primarily classified into three categories: A (21/124, 16.9%), B1 (96/124, 77.4%), and B2 (7/124, 5.6%), with 37 distinct sequence types (STs), including the newly identified ST16626. PCR-based virulence gene screening detected 24 virulence genes, with ompA and fimC exhibiting universal prevalence (100%), followed by luxS (96.8%), etrA (79.8%), and flu (72.6%). Antibiotic resistance gene profiling identified five major categories: tetracyclines (tetA 20.97%, tetB 29.03%, tetC 4.84%, tetD 4.84% and tetM 2.42%), sulfonamides (sul1 21.77%, sul2 28.23% and sul3 9.68%), quinolones (qnrS 6.45%), β-lactams (blaTEM 88.71%, blaSHV 7.26%, CTX-M12.42%, CTX-M8 11.29% and CTX-M9 11.29%), and aminoglycosides (cat1 67.74%, cat2 54.03%, aadA2 10.48%, aac(6')-Ib 9.68% and aph(3')-vII 4.84%). Antimicrobial susceptibility testing demonstrated resistance rates below 50% for all 12 tested drugs, with the highest prevalence observed for tetracycline (TCY, 41.94%), cefotaxime (CTX, 36.29%), ampicillin (AMP, 34.68%), and ciprofloxacin (CIP, 33.06%). Conclusions This study presents the first systematic elucidation of molecular epidemiological characteristics of E. coli in the Qinghai Plateau: Identification of 37 sequence types (including novel ST16626) revealed significant phylogenetic divergence between yak- and wildlife-derived strains and the recA gene deficiency phenomenon; Discovery of host-specific resistance-virulence gene profiles confirmed differential evolutionary adaptation; The findings provide molecular evidence for zoonotic disease risk early-warning and clarify the driving mechanism of livestock farming on antimicrobial resistance transmission.