Evidence of vancomycin-resistant Staphylococcus aureus, multidrug-resistant S. aureus, and Enterococcus faecium-causing mastitis in Thailand and Cambodia

Vet World Vol.18 January-2025 Article - 22

Research Article

Veterinary World, 18(1): 202-209

https://doi.org/10.14202/vetworld.2025.202-209

Sambo Na¹, Montira Intanon^2,3, Anyaphat Srithanasuwan^2,4, Wasana Chaisri^2,3, and Witaya Suriyasathaporn^2,3,5

1. Master’s Degree Program in Veterinary Science, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai, 50100, Thailand.
2. School of Veterinary Medicine, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai, 50100, Thailand.
3. Research Center of Producing and Development of Products and Innovations for Animal Health, Chiang Mai University, Chiang Mai, 50100, Thailand.
4. Department of Animal Sciences, Wageningen University, 6708, PB Wageningen, The Netherlands.
5. Cambodia-Campuses, Asian Satellite Campuses Institute, Nagoya University, Japan.

Background and Aim: Bovine mastitis, an inflammatory condition of the mammary gland, is a critical economic issue in the dairy industry. Antimicrobial resistance (AMR) to mastitis-causing pathogens poses a significant threat to dairy operations in Thailand and Cambodia. This study investigates the AMR of mastitis pathogens in Thailand and Cambodia. It focuses on detecting methicillin-resistant Staphylococcus aureus, vancomycin-resistant S. aureus (VRSA), and vancomycin-resistant enterococci by identifying the presence of mecA, vanA, and vanB genes in bacterial isolates.

Materials and Methods: A total of 65 bacterial isolates (55 S. aureus from Thailand and 10 Enterococcus faecium from Thailand and Cambodia) were analyzed. Disk diffusion tests were conducted for antibiotic susceptibility, and polymerase chain reaction was employed to detect AMR genes.

Results: S. aureus isolates showed resistance to penicillin (21.8%), tetracycline (9.1%), and gentamycin (7.3%). Three isolates were identified as multidrug-resistant (MDR), resistant to tetracycline, gentamycin, and penicillin. E. faecium isolates exhibited high resistance to tetracycline (100%) and penicillin (90%), with 60% classified as MDR. Phenotypic analysis identified VRSA in 11% of S. aureus isolates. However, mecA, vanA, and vanB genes were not detected in any isolate.

Conclusion: Mastitis pathogens in this study pose significant AMR challenges, especially with MDR S. aureus and E. faecium, and phenotypically VRSA without the vanA gene. The findings highlight the need for judicious antibiotic use in dairy farms and further studies with broader sampling.

Keywords: antimicrobial resistance, dairy farms, mastitis, methicillin-resistant Staphylococcus aureus, multidrug resistance, vancomycin-resistant enterococci, vancomycin-resistant Staphylococcus aureus.

How to cite this article: Na S, Intanon M, Srithanasuwan A, Chaisri W, and Suriyasathaporn W (2025) Evidence of vancomycin-resistant Staphylococcus aureus, multidrug-resistant S. aureus, and Enterococcus faecium-causing mastitis in Thailand and Cambodia, Veterinary World, 18(1): 202–209.

Received: 2024-08-29 Accepted: 2024-12-10 Published online: 2025-01-30

Corresponding author: Montira Intanon E-mail: montira.intanon@cmu.ac.th

DOI: 10.14202/vetworld.2025.202-209

Copyright: Na, 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.