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Animals : an open access journal from MDPI2025; 15(23); 3413; doi: 10.3390/ani15233413

Prevalence and Antimicrobial Resistance Patterns of Salmonella in Asymptomatic Horses in Eastern Spain: A One Health Perspective.

Abstract: are zoonotic pathogens, and rising antimicrobial resistance (AMR) amplifies their public health impact. Asymptomatic horses can act as reservoirs, contributing to environmental contamination and interspecies transmission. This study aimed to estimate the prevalence of and characterize AMR patterns in healthy horses from eastern Spain. Faecal samples from 95 asymptomatic horses were collected once daily over five consecutive days (475 samples in total) and processed under for detection. Epidemiological information was obtained through owner questionnaires, and associations with shedding were analyzed using generalized linear models. Antimicrobial susceptibility was assessed by minimum inhibitory concentration assays following the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. was detected in 25.3% of horses (24/95), with S. Enteritidis, S. Johannesburg, and S. Virchow as the most frequent serotypes. A significant association was observed between proximity of manure storage and bacterial detection ( < 0.001). Among 24 isolates of , 88.9% were resistant to at least one antimicrobial, and 50% exhibited multidrug resistance. The highest resistance rates were against sulfamethoxazole and gentamicin, followed by ciprofloxacin and tigecycline. Healthy horses can act as silent carriers of multidrug-resistant , highlighting the need for surveillance, strengthened biosecurity, and prudent antimicrobial use within a One Health framework.
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Publication Date: 2025-11-26 PubMed ID: 41375470PubMed Central: PMC12691379DOI: 10.3390/ani15233413Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Research Overview

  • This study investigated how common Salmonella bacteria are in healthy horses in eastern Spain and examined the patterns of antimicrobial resistance (AMR) in these bacteria.
  • The research aimed to understand the potential role of asymptomatic horses as carriers of multidrug-resistant Salmonella, which has implications for animal, environmental, and human health.

Introduction and Background

  • Salmonella is a genus of bacteria known to cause infections in both animals and humans, making them zoonotic pathogens.
  • Antimicrobial resistance (AMR) in Salmonella increases the difficulty of treating infections, posing a growing public health challenge worldwide.
  • Horses that carry Salmonella without showing symptoms (asymptomatic carriers) can serve as reservoirs of the bacteria.
  • These horses contribute to environmental contamination and may facilitate the transmission of Salmonella between different species, including humans.
  • This study applies a One Health perspective—which integrates human, animal, and environmental health—to address this complex issue.

Objectives of the Study

  • Estimate the prevalence of Salmonella shedding in healthy, asymptomatic horses in eastern Spain.
  • Characterize the antimicrobial resistance patterns of Salmonella isolates found in these horses.
  • Identify epidemiological factors that may be associated with the carriage of Salmonella in horses.

Methodology

  • Sample Collection:
    • Faecal samples were collected from 95 healthy horses.
    • Sampling occurred once daily over five consecutive days resulting in a total of 475 samples.
  • Detection:
    • Samples were tested to detect the presence of Salmonella bacteria.
  • Epidemiological Data:
    • Information was gathered through questionnaires filled out by horse owners.
    • This data helped analyze possible associations between environmental or management factors and Salmonella shedding.
  • Statistical Analysis:
    • Generalized linear models were used to explore associations between variables and Salmonella presence.
  • Antimicrobial Susceptibility Testing:
    • The minimum inhibitory concentration (MIC) assays were performed following European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines.
    • This method determines bacterial resistance levels to various antimicrobials.

Key Findings

  • Prevalence:
    • Salmonella was detected in 25.3% of the sampled horses (24 out of 95 horses).
  • Common Serotypes:
    • The most frequent Salmonella serotypes identified were S. Enteritidis, S. Johannesburg, and S. Virchow.
  • Epidemiological Associations:
    • There was a statistically significant correlation between the proximity of manure storage areas to where horses were kept and the likelihood of Salmonella detection (p < 0.001).
  • Antimicrobial Resistance:
    • Among the 24 Salmonella isolates, 88.9% were resistant to at least one antimicrobial agent.
    • Half of the isolates (50%) showed multidrug resistance (resistance to three or more antimicrobial classes).
    • Resistance was most common against sulfamethoxazole and gentamicin.
    • Other notable antimicrobials showing resistance included ciprofloxacin and tigecycline.

Implications and Recommendations

  • Healthy horses can act as hidden carriers of multidrug-resistant Salmonella, potentially transmitting these bacteria to other animals, humans, and the environment.
  • Manure management practices play a significant role in the presence and spread of Salmonella, implying the need to improve biosecurity measures around manure storage.
  • To mitigate public and animal health risks, the study highlights the need for:
    • Regular surveillance programs to monitor Salmonella and its antimicrobial resistance in horses.
    • Enhanced biosecurity protocols to prevent environmental contamination and cross-species transmission.
    • Prudent use of antimicrobials in veterinary medicine, to reduce the development and spread of AMR.
  • Overall, adopting an integrated One Health approach is critical to effectively address the risks posed by Salmonella in horses.

Cite This Article

APA
Simó-Martínez MS, Marco-Fuertes A, Galán-Relaño Á, Astorga Márquez RJ, Marin C, Valero Díaz A, Vega S. (2025). Prevalence and Antimicrobial Resistance Patterns of Salmonella in Asymptomatic Horses in Eastern Spain: A One Health Perspective. Animals (Basel), 15(23), 3413. https://doi.org/10.3390/ani15233413

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 15
Issue: 23
PII: 3413

Researcher Affiliations

Simó-Martínez, María Socorro
  • Department of Animal Medicine and Surgery, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Valencia, Spain.
Marco-Fuertes, Ana
  • Department of Animal Production and Health, Public Veterinary Health and Food Science and Technology, Faculty of Veterinary Medicine, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Valencia, Spain.
Galán-Relaño, Ángela
  • Department of Nursing, Pharmacology and Physiotherapy Area, Faculty of Veterinary Medicine, University of Cordoba, 14014 Cordoba, Spain.
Astorga Márquez, Rafael J
  • Animal Health Department, Veterinary Faculty, University of Cordoba, 14014 Cordoba, Spain.
Marin, Clara
  • Department of Animal Production and Health, Public Veterinary Health and Food Science and Technology, Faculty of Veterinary Medicine, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Valencia, Spain.
Valero Díaz, Antonio
  • Food Science and Technology Department, Veterinary Faculty, University of Cordoba, 14014 Cordoba, Spain.
Vega, Santiago
  • Department of Animal Production and Health, Public Veterinary Health and Food Science and Technology, Faculty of Veterinary Medicine, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Valencia, Spain.

Conflict of Interest Statement

The authors declare no conflicts of interest.

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