Prevalence, antimicrobial resistance and molecular homology of diarrheagenic Escherichia coli isolated from Highland Tibetan herdsmen in Nagqu, Tibet, China.

Authors

Hui Pan, Xinyue Han, Hongwei Zhou, Lun Zhang

Published in

Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases. Pages 105986. Jul 09, 2026. Epub Jul 09, 2026.

Abstract

Diarrheagenic Escherichia coli (DEC) is a leading cause of infectious diarrhea globally, yet its epidemiology in high-altitude human populations remains largely unexplored. This study aimed to determine the prevalence, pathotype distribution, antimicrobial resistance, and genetic diversity of DEC among Tibetan herdsmen in Nagqu, Tibet, China, during June 2025, with comparison to a low-altitude cohort from Zhejiang Province.
In this cross-sectional, observational study, a total of 209 fecal samples were collected from Tibetan herdsmen in Nagqu. DEC isolates were identified by MALDI-TOF MS and PCR-based pathotyping. Antimicrobial susceptibility was assessed by broth microdilution, and genetic relatedness was evaluated using Fourier-transform infrared (FT-IR) spectroscopy. For ecological comparison, 187 DEC isolates from 799 fecal samples in Zhejiang Province were analyzed using identical molecular methods.
Of 111 confirmed E. coli isolates from Nagqu, 36 (32.4%, 95% CI: 23.8%-42.1%) were identified as DEC, including 32 EAEC, 2 STEC/EPEC, and 2 STEC strains. The predominant virulence genes were aggR (50.0%) and astA (47.2%). All isolates were susceptible to β-lactam/β-lactamase inhibitor combinations, carbapenems, and tigecycline, while moderate resistance was observed to ampicillin (38.9%) and cefazolin (27.8%). FT-IR typing revealed 36 distinct lineages, indicating an absence of clonal clustering among DEC isolates. Pathotype distribution in Nagqu (EAEC predominance, 88.9%) differed markedly from that in Zhejiang, where EAEC (51.9%) and STEC/EPEC (47.6%) were co-dominant.
DEC in this high-altitude population exhibits an EAEC-dominated pathotype profile, low antimicrobial resistance, and remarkable genetic heterogeneity. These findings suggest that rather than micro-evolutionary adaptations to high altitude, the remote, low-antibiotic pastoral environment acts as an evolutionary sanctuary that preserves ancestral, non-clonal lineages and restricts the selective sweeps of multidrug-resistant clones common in lowlands. This unique baseline provides a data-driven rationale for integrating nomadic populations into national surveillance; monitoring this pristine pathogen ecology within a One Health framework offers a vital evolutionary control to better track and mitigate enteric pathogen dissemination across socio-ecologically diverse settings.

PMID:
42425383
Bibliographic data and abstract were imported from PubMed on 10 Jul 2026.

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