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Research Article | 10 Aug 2026

Antimicrobial resistance profiles of commensal Escherichia coli from pasture-raised sheep, goats, and cattle in Mongolia: Baseline surveillance in an extensive pastoral production system

Enkhsaikhan Ochirkhuyag1,2 ORCID , Bolormaa Tsognemekh3 ORCID , Chantsal Batsaikhan3 ORCID , Davaasuren Nergui3 ORCID , Bayarbat Ishvaanjil4 ORCID , Nyamdavaa Guugandaa3 ORCID , Erdene-Ochir Tseren-Ochir3 ORCID , Delgertsetseg Sodnomdarjaa5 ORCID , Enkhtur Byakharjav5 ORCID , and Uyangaa Temuujin1,3 ORCID Show more
INTERNATIONAL JOURNAL OF ONE HEALTH | Article No. 8 | pg no. 292-302 | Vol. 12, Issue 2 | DOI: 10.14202/IJOH.2026.292-302
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ABSTRACT

                      
Background and Aim: Antimicrobial resistance (AMR) is a growing global One Health concern, yet surveillance data from extensive pastoral livestock systems remain limited, particularly in Central Asia. Mongolia's pasture-based livestock production system provides a unique opportunity to evaluate AMR under relatively low antimicrobial selection pressure. This study aimed to characterize and compare the antimicrobial susceptibility profiles of commensal Escherichia coli isolated from healthy pasture-raised sheep, goats, and cattle in Mongolia and to establish baseline evidence for national and international AMR surveillance. 
Materials and Methods: A cross-sectional surveillance study was conducted between August and November 2025. Caecal content samples were collected from 151 clinically healthy livestock comprising 50 sheep, 50 goats, and 51 cattle originating from 13 provinces and processed at six registered slaughter facilities. A total of 150 E. coli isolates were identified using the VITEK 2 COMPACT automated identification system and evaluated for susceptibility to 11 antimicrobial agents representing eight antimicrobial classes by the Kirby–Bauer disk diffusion method according to the Clinical and Laboratory Standards Institute 2024 guidelines. Differences in AMR among livestock species were assessed using Fisher's exact test, with p < 0.05 considered statistically significant. 
Results: Overall antimicrobial susceptibility was high across all livestock species. All E. coli isolates were fully susceptible to ceftazidime and chloramphenicol, while susceptibility to cefotaxime exceeded 96% in all species. Resistance to tetracycline, ampicillin, nalidixic acid, and trimethoprim–sulfamethoxazole remained low, with no significant differences among livestock species (p > 0.05). Intermediate susceptibility to streptomycin was significantly more frequent in sheep (34%) than in goats (14%) and cattle (4%) (p < 0.05). Multidrug resistance was detected in only 2% of isolates and occurred predominantly among sheep-derived isolates resistant to three or more antimicrobial classes. The predominance of susceptible isolates indicates limited antimicrobial selection pressure in Mongolia's extensive pastoral production system, although the presence of intermediate susceptibility and multidrug-resistant isolates suggests emerging resistance that warrants continued monitoring. 
Conclusion: Commensal E. coli isolated from pasture-raised livestock in Mongolia exhibited predominantly favorable antimicrobial susceptibility profiles, supporting the hypothesis that extensive grazing systems are associated with relatively low antimicrobial selection pressure. Nevertheless, the detection of intermediate susceptibility and multidrug-resistant isolates highlights the need for sustained phenotypic surveillance, strengthened antimicrobial stewardship, and future molecular investigations within an integrated One Health framework. These findings provide robust baseline evidence to support Mongolia's National Action Plan on AMR and strengthen regional and global AMR surveillance initiatives. 
                      
Keywords: antimicrobial resistance, baseline surveillance, commensal Eshcherichia coli, extensive pastoral system, livestock, Mongolia, One Health, pasture-raised livestock.