Antimicrobial resistance, extended-spectrum β-lactamase determinants, and virulence gene profiles of Escherichia coli along the pork production chain in central Thailand

Vet World Vol.19 January-2026 Article - 5

Research Article

Veterinary World, 19(1): 52-64

https://doi.org/10.14202/vetworld.2026.52-64

Watsawan Prapasawat¹

, Achiraya Siriphap²

, Sirikarn Wiriyasirivaj¹

, Apiradee Intarapuk³

, Ruttana Pachanon⁴

, Chie Nakajima^4,5

, Yasuhiko Suzuki^4,6,7

, and Orasa Suthienkul^8,9

1. Department of Clinic, Faculty of Veterinary Medicine, Mahanakorn University of Technology, Bangkok 10530, Thailand.

2. Division of Microbiology and Parasitology, School of Medical Sciences, University of Phayao, Phayao 56000, Thailand.

3. Department of Science, Technology and Innovation, Faculty of Science, Chulabhorn Royal Academy, Bangkok, Thailand.

4. Division of Bioresources, Hokkaido University International Institute for Zoonosis Control, Sapporo, Japan.

5. International Collaboration Unit, Hokkaido University International Institute for Zoonosis Control, Sapporo, Japan. .

6. International Collaboration Unit, Hokkaido University International Institute for Zoonosis Control, Sapporo, Japan.

7. Hokkaido University Institute for Vaccine Research and Development, Sapporo, Japan. .

8. Faculty of Public Health, Thammasat University ( Rangsit Campus), Pathumthani 12121, Thailand.

9. Faculty of Public Health, Mahidol University, Bangkok 10400, Thailand. .

Background and Aim: Antimicrobial resistance (AMR) in foodborne bacteria presents a significant threat to public health, especially in countries with intensive livestock production systems. Pig farming is a major source of animal protein in Thailand and is recognized as an important reservoir of antimicrobial-resistant bacteria. Escherichia coli is commonly used as an indicator organism for monitoring AMR, including extended-spectrum β-lactamase (ESBL) production and pathogenic potential. This study aimed to assess the frequency of AMR, multidrug-resistant (MDR), ESBL determinants, and virulence genes in E. coli isolates collected from slaughterhouses and fresh markets in central Thailand.

Materials and Methods: A total of 498 archived E. coli isolates were analyzed, including 236 isolates from slaughterhouses (feces and carcasses) and 262 isolates from fresh markets (pork and cutting boards). Antimicrobial susceptibility testing was performed against 18 antimicrobial agents using the disk diffusion method. MDR was defined as resistance to three or more antimicrobial classes. ESBL production was identified through phenotypic confirmatory tests, and ESBL-producing isolates were screened for blaTEM, blaCTX-M, and blaSHV genes by multiplex polymerase chain reaction. All isolates were further examined for select virulence genes linked to major E. coli pathotypes.

Results: Overall, 97.4% of E. coli isolates showed resistance to at least one antimicrobial agent, and 87.3% were classified as MDR. ESBL-producing E. coli made up 23.5% of all isolates, with a significantly higher prevalence in slaughterhouses compared to fresh markets (p < 0.05). Among ESBL producers, 97.4% exhibited MDR phenotypes. Most (89.7%) of the ESBL-producing isolates carried at least one bla gene, with blaTEM being the most common, followed by blaCTX-M. Virulence genes were detected at a low frequency (3.2%), mainly involving eaeA, lt, and stp.

Conclusion: The high prevalence of AMR, MDR, and ESBL-producing E. coli throughout the pork production chain highlights slaughterhouses and fresh markets as key points for the spread of resistant bacteria. These findings emphasize the need for stronger antimicrobial stewardship, better hygiene practices, and ongoing AMR surveillance within the One Health approach to reduce public health risks linked to pork consumption.

Keywords: antimicrobial resistance, extended-spectrum beta-lactamase, Escherichia coli, food safety, multidrug resistance, pork production chain, slaughterhouse contamination, Thailand, virulence genes.

How to cite this article: Prapasawat W, Siriphap A, Wiriyasirivaj S, Intarapuk A, Pachanon R, Nakajima C, Suzuki Y, Suthienkul O. Antimicrobial resistance, extended-spectrum β-lactamase determinants, and virulence gene profiles of Escherichia coli along the pork production chain in central Thailand. Vet World. 2026;19(1):52–64.

Received: 11-08-2025 Accepted: 15-12-2025 Published online: 08-01-2026

Corresponding author: Orasa Suthienkul E-mail: orasa.sut@mahidol.ac.th

DOI: 10.14202/vetworld.2026.52-64

Copyright: Prapasawat , et al. This article is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.