Emergence of ciprofloxacin- and tigecycline-resistant extended-spectrum β-lactamase (ESBL)-producing Salmonella enterica serovar Kentucky ST198 from horse, China

Xing-Xing Zhang; Xin Huang; Xue-Qin Li; Zhen-Yu Wang; Yue Jiang; Xinan Jiao; Qiuchun Li; Jing Wang; Fa-Gang Zhong

doi:10.1016/j.jgar.2025.06.020

Emergence of ciprofloxacin- and tigecycline-resistant extended-spectrum β-lactamase (ESBL)-producing Salmonella enterica serovar Kentucky ST198 from horse, China

J Glob Antimicrob Resist. 2025 Jul 2:S2213-7165(25)00153-5. doi: 10.1016/j.jgar.2025.06.020. Online ahead of print.

Authors

Xing-Xing Zhang¹, Xin Huang¹, Xue-Qin Li¹, Zhen-Yu Wang², Yue Jiang², Xinan Jiao², Qiuchun Li³, Jing Wang⁴, Fa-Gang Zhong⁵

Affiliations

¹ State Key Laboratory for Sheep Genetic Improvement and Healthy Production, Institute of Animal Husbandry and Veterinary, Xinjiang Academy of Agricultural and Reclamation Science, Shihezi, Xinjiang 832000, China.
² Jiangsu Key Laboratory of Zoonosis/Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China.
³ State Key Laboratory for Sheep Genetic Improvement and Healthy Production, Institute of Animal Husbandry and Veterinary, Xinjiang Academy of Agricultural and Reclamation Science, Shihezi, Xinjiang 832000, China; Jiangsu Key Laboratory of Zoonosis/Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China.
⁴ Institute of Medical Sciences, School of Public Health, Xinjiang Medical University, Urumqi 830017, China. Electronic address: wj1231@xjmu.edu.cn.
⁵ State Key Laboratory for Sheep Genetic Improvement and Healthy Production, Institute of Animal Husbandry and Veterinary, Xinjiang Academy of Agricultural and Reclamation Science, Shihezi, Xinjiang 832000, China. Electronic address: zfg125@sohu.com.

PMID: 40615037
DOI: 10.1016/j.jgar.2025.06.020

Abstract

Objective: Salmonella enterica serovar Kentucky ST198 has been increasingly reported in diverse sources worldwide, emerging as a globally epidemic clone. In this study, we aim to characterize the first isolated S. Kentucky ST198 strain from a horse in China.

Methods: Twelve fecal samples were collected from horses at a farm in Shihezi, Xinjiang Province, China, and investigated for the presence of Salmonella. The minimum inhibitory concentrations of 15 antimicrobial agents were determined using the broth microdilution method. The whole genome of Sal140 was sequenced using the Illumina Hiseq platform and assembled into contigs with SPAdes 3.10.0. Phylogenetic analysis was performed using Parsnp based on core-genome single-nucleotide polymorphisms.

Results: A single S. Kentucky strain, designated Sal140, was isolated. This strain carried 15 antimicrobial resistance genes and exhibited resistance to ampicillin, ceftazidime, cefuroxime, cefotaxime, gentamicin, streptomycin, tetracycline, tigecycline, florfenicol, nalidixic acid, ciprofloxacin, azithromycin, and sulfamethoxazole/trimethoprim. Co-resistance to ciprofloxacin and third-generation cephalosporins was attributed to mutations in gyrA (S83F and D87G) and parC (T57S and S80I), and the production of CTX-M-55, respectively. Phylogenetic analysis revealed that Sal140 clustered within the subclade ST198.2-2, showing close genetic similarity (15-24 SNPs) to isolates from a patient and chicken meat in other regions of China, suggesting a potential epidemiological link among these S. Kentucky ST198 isolates from different sources.

Conclusion: In conclusion, the emergence of extensively drug-resistant (XDR) S. Kentucky ST198 in a horse is concerning. Continuous surveillance of this particular clone in horses is strongly recommended.

Keywords: CTX-M; ST198; Salmonella enterica serovar Kentucky; extensively drug-resistant; horse.