Antimicrobial Resistance: What the Research Says
Evidence from 23 peer-reviewed studies
What Professionals Should Know
- •When treating suspected P. aeruginosa infections in equines, consider resistance patterns in your region and favor aztreonam, fosfomycin, ciprofloxacin, or ceftazidime based on culture and sensitivity results
- •Avoid routine use of imipenem, amikacin, and ceftiofur for P. aeruginosa without confirmed susceptibility, as resistance rates are rising across multiple regions
- •Implement strict antimicrobial stewardship practices in your facility, including culture-based diagnostics before treatment and avoiding broad-spectrum agents when narrower options are effective
- •Understanding which zoonotic bacteria are prevalent in veterinary hospitals helps inform infection control protocols and personal protective equipment use in your facility
- •Antimicrobial susceptibility data should guide treatment decisions for hospital-acquired infections to combat resistance patterns in your specific setting
- •Consider screening and isolation protocols for high-risk patients to reduce HAI transmission and associated treatment costs
- •Your practice management software can be used to generate standardized antibiotic usage reports that allow meaningful comparison with other practices and tracking of resistance management progress
- •Using defined daily dose calculations rather than simple mg/kg measurements may better reflect actual antibiotic exposure in equine practice, particularly given the heavy reliance on potentiated sulphonamides
- •Accurate record-keeping of antibiotic preparations in your software is essential for reliable monitoring; this supports both antimicrobial stewardship audits and compliance with resistance prevention strategies
- •Nearly half of healthy horses carry multidrug-resistant bacteria in their gut; implement enhanced biosecurity protocols, particularly around staff numbers and event participation, to reduce spread within facilities
- •Equestrian event participation is a significant risk factor for MDR E. coli shedding—establish hygiene practices and consider screening protocols before attending competitions or moving horses between premises
- •The high prevalence of resistant gram-negative bacteria warrants judicious antibiotic use and culture-guided therapy in equine practice; reserve β-lactam antibiotics and monitor treatment response carefully
- •Be aware that S. aureus infections in horses carry significant antimicrobial resistance patterns, particularly multidrug resistance, which can transfer to humans—inform clients and use targeted rather than broad-spectrum treatments when possible
- •Tetracycline resistance is widespread across most equine bacterial isolates, limiting its utility as empirical therapy; consider local resistance data when selecting initial antimicrobial treatments
- •Third-generation cephalosporins remain effective options for Enterobacteriaceae infections in horses, as resistance rates remain low; reserve these for serious infections to preserve their utility
- •Understanding local antimicrobial resistance patterns in your region helps guide empirical antibiotic selection before culture results return, reducing treatment failures and costs
- •Certain horse breeds and sample sources may be associated with higher resistance rates—tailor diagnostic protocols and treatment strategies accordingly
- •Monitor temporal trends in resistance at your diagnostic laboratory to stay current with emerging resistance patterns and adjust therapeutic recommendations
- •Implement strict biosecurity protocols in teaching hospitals and equine facilities to prevent transmission of methicillin-resistant staphylococci between horses and personnel
- •Nasal carriage of MRS in hospitalized horses and staff represents a zoonotic risk; routine screening may be warranted in high-risk settings
- •Veterinarians and stable staff should practice enhanced hygiene measures (hand washing, appropriate PPE) when handling hospitalized horses, particularly those with suppurative conditions
- •Healthy riding horses are asymptomatic reservoirs for antimicrobial-resistant E. coli; implement biosecurity and hygiene protocols when handling horses and equipment to reduce zoonotic transmission risk
- •E. coli isolated from horses shows resistance to commonly prescribed antibiotics, informing treatment decisions if equine E. coli infections are suspected
- •Consider horses as a potential source of resistant pathogens when evaluating human infections in people with horse contact, and discuss infection control with horse owners and veterinarians
- •Over half of E. coli isolates from Turkish horse farms produce ESBLs, making standard beta-lactam antibiotics unreliable for treatment of bacterial infections on these farms
- •The high prevalence of multidrug-resistant strains with multiple resistance genes suggests routine susceptibility testing should be performed before prescribing antibiotics for equine infections
- •Veterinarians should implement strict antibiotic stewardship protocols and consider alternative treatment options, as many common antibiotics may be ineffective against these resistant E. coli strains
- •Healthy horses are a significant reservoir for potentially virulent S. aureus strains; consider infection control measures during slaughter and processing to prevent human foodborne transmission
- •The majority of staphylococcal isolates show low antibiotic resistance, but awareness of resistance patterns is important for treatment decisions if clinical infections occur
- •S. aureus carriage is common in healthy horses without clinical signs; routine screening may not be necessary unless clinical mastitis or wound infections are present
- •Request culture and sensitivity testing for suspected Staphylococcus infections rather than assuming standard antimicrobial protocols will be effective
- •Implement enhanced biosecurity and hygiene protocols when handling horses with confirmed resistant Staphylococcus to protect yourself, other staff, and owners from zoonotic transmission
- •Work with your veterinarian to establish local antimicrobial resistance patterns in your region to guide empirical treatment decisions
- •Healthy horses can harbour multidrug-resistant enterococci without clinical signs, posing a zoonotic and cross-contamination risk in equine facilities
- •Vancomycin-resistant enterococci in horse populations may complicate treatment options for serious infections in both horses and humans
- •Biosecurity and hygiene protocols in stables should consider antimicrobial-resistant pathogens as a potential hidden health risk
- •Understanding owner attitudes and practices regarding antimicrobial use is essential for developing effective stewardship strategies that will reduce resistance while maintaining equine health
- •Future stewardship interventions should be evidence-based and tailored to equine owner beliefs and behaviors rather than generic approaches
- •Veterinarians working with horse owners should assess individual knowledge gaps and concerns about antimicrobial use to improve compliance with responsible use protocols
- •Macroalgae-based supplements show promise as natural alternatives to antimicrobial and anthelmintic drugs given emerging resistance concerns, but evidence in horses specifically remains limited
- •Seaweed's nutritional profile and bioactive compounds may support equine gastrointestinal health and welfare, though manufacturer claims require further substantiation through rigorous research
- •Until regulation and standardization improve, veterinarians should exercise caution with macroalgae supplements and recommend only those with documented safety profiles
- •Implement documented stop/review dates for all antibiotic courses to reduce unnecessary prolonged use and support antimicrobial stewardship in your hospital
- •Establish protocols requiring biomarker testing (e.g., clinical signs, blood work) before initiating therapeutic antibiotics, particularly for surgical prophylaxis decisions
- •Submit bacterial culture samples routinely before starting therapeutic antibiotics and use antibiogram results to guide empiric antibiotic selection rather than defaulting to broad-spectrum options
- •Evaluate whether your practice has a written antimicrobial stewardship policy and implement one if absent, as this is becoming standard practice
- •Review your surgical prophylaxis protocols—consider whether post-operative antimicrobials are truly necessary for clean surgeries, as this may contribute to unnecessary resistance development
- •Establish basic surveillance and audit processes for clinical infections and infection control to identify resistance patterns and inform prescribing decisions
- •Evaluate your prescribing practices against current antimicrobial stewardship guidelines to ensure you are not contributing to resistance development in your patient population
- •Use ceftiofur judiciously and only when indicated by clinical evidence; follow equine-specific dosing and duration recommendations rather than extrapolating from other species
- •Stay informed about local and regional resistance patterns to cephalosporins in horses to make informed treatment decisions
- •While horses and other livestock can carry ESBL-producing E. coli, human-to-human transmission (particularly in healthcare settings) represents the primary risk pathway for community infections—hygiene protocols should prioritize this route
- •Equine practitioners should be aware that horses are potential reservoirs for resistant bacteria, but direct zoonotic transmission to humans appears less significant than healthcare-associated transmission
- •A coordinated One Health approach integrating animal, environmental, and human surveillance data is needed to effectively monitor and control ESBL-producing E. coli transmission
- •Equine platelet lysate shows promise as a biological antimicrobial agent, though clinical application requires further in vivo validation before practical implementation
- •Different bacterial species respond differently to platelet lysate, suggesting dosing and clinical protocols would need to be tailored by organism type
- •This research provides foundational evidence for developing alternatives to conventional antibiotics in equine medicine, addressing growing antimicrobial resistance concerns
- •Question routine prophylactic intra-articular antibiotic use in your practice, as many common choices damage healthy joint cells while potentially driving resistance
- •Work with your veterinarian to identify and use antibiotics with lower cytotoxic profiles when intra-articular injection is necessary, and ensure proper dosing protocols are established
- •Consider alternative joint health strategies and reserve intra-articular antibiotics for clear therapeutic indications rather than automatic prophylaxis
- •Clinicians should be aware of emerging antimicrobial resistance patterns when selecting antibiotics for equine infections
- •Prudent antimicrobial stewardship practices are essential to minimize resistance development in equine medicine
- •Monitoring of resistance trends in equine pathogens should inform treatment protocols and therapeutic choices
- •Equine practitioners should prioritize access to affordable, rapid diagnostic testing to reduce unnecessary broad-spectrum antibiotic prescribing and support antimicrobial stewardship.
- •Cost barriers to culture and susceptibility testing are a major obstacle to evidence-based prescribing—consider advocating for laboratory fee structures that encourage diagnostic confirmation.
- •Awareness of your prescribing patterns and their contribution to antimicrobial resistance is an important first step; seek sector-specific stewardship guidance tailored to equine practice.
- •Equine practitioners should review their own antimicrobial prescribing practices and consider adopting stewardship principles, as regulatory oversight is limited in North America
- •Be aware that prescribing choices may have implications for human medicine; using alternatives to critically important antimicrobials when possible helps preserve their effectiveness
- •Large-scale data analysis can reveal prescribing patterns and identify opportunities to improve practice standards and reduce unnecessary antimicrobial use
Key Research Findings
Analysis of 1,624 P. aeruginosa isolates from 10 equine studies revealed high resistance rates to imipenem, amikacin, and ceftiofur with increasing temporal trends
Asia reported the highest average antimicrobial resistance rates, suggesting regional differences in antimicrobial use patterns
Aztreonam, fosfomycin, ciprofloxacin, and ceftazidime demonstrated the most consistent antimicrobial efficacy against equine-associated P. aeruginosa
Generalizability of findings is limited by only 10 eligible studies and uneven distribution of isolate testing across antimicrobial classes
Hospital-acquired infections in veterinary settings are commonly caused by zoonotic bacterial pathogens with significant antimicrobial resistance profiles
HAIs are associated with increased mortality, morbidity, and substantial economic burden due to prolonged hospitalization
Multiple bacterial organisms identified in veterinary hospitals demonstrate varying susceptibility patterns to antimicrobial agents
Median annual antibiotic usage across 14 UK equine practices was 54.25 mg/kg (range 45.34-60.27 mg/kg) over the 10-year period 2012-2021
Critically important antimicrobial usage (HPCIA) was relatively low at a median of 0.67 mg/kg (range 0.56-1.71 mg/kg)
Defined daily dose metrics (DDDvet and DDD/1000 animals) were successfully calculated to standardize antibiotic usage reporting across practices despite varying dosing regimens
Software-based monitoring using practice management systems provides a reliable method for tracking antibiotic usage trends and supporting antimicrobial stewardship in equine practice
46.3% of healthy horses in Quebec shed multidrug-resistant E. coli in feces
7.3% of horses harbored ESBL/AmpC-producing E. coli, with blaCTX-M-1 as the most common gene identified
Non-susceptibility was most common to ampicillin, amoxicillin/clavulanic acid, and streptomycin
Number of staff and equestrian event participation were identified as risk factors for shedding MDR isolates
Evidence Base
Prevalence of antimicrobial resistance in equine-associated Pseudomonas aeruginosa: a systematic review and meta-analysis.
Yang Luo, Xie Yuxin, Zhong Guangzhi et al. (2025) — BMC veterinary research
Hospital-acquired and zoonotic bacteria from a veterinary hospital and their associated antimicrobial-susceptibility profiles: A systematic review.
Sebola Dikeledi C, Oguttu James W, Kock Marleen M et al. (2022) — Frontiers in veterinary science
Antibiotic usage in 14 equine practices over a 10-year period (2012-2021).
Tallon Rose E, Whitt Brian, Bladon Bruce M (2024) — Equine veterinary journal
de Lagarde Maud, Fairbrother John M, Arsenault Julie (2020) — Animals : an open access journal from MDPI
Antimicrobial resistance in bacteria isolated from diseased horses in France.
Bourély C, Cazeau G, Jarrige N et al. (2020) — Equine veterinary journal
An epidemiologic study of antimicrobial resistance of Staphylococcus species isolated from equine samples submitted to a diagnostic laboratory.
Adams Ronita, Smith Jackie, Locke Stephen et al. (2018) — BMC veterinary research
Methicillin-resistant Staphylococcus spp. investigation in hospitalized horses and contacting personnel in a teaching veterinary hospital.
Olivo Giovane, Zakia Luiza Stachewski, Ribeiro Márcio Garcia et al. (2024) — Journal of equine veterinary science
Molecular characterization and antimicrobial resistance of potentially human-pathogenic Escherichia coli strains isolated from riding horses.
Reshadi Pouya, Heydari Fatemeh, Ghanbarpour Reza et al. (2021) — BMC veterinary research
Antimicrobial Resistance and Extended-Spectrum Beta-Lactamase (ESBL) Genes in E. coli Isolated from Equine Fecal Samples in Turkey.
Yiğin Akın (2021) — Journal of equine veterinary science
Mama Olouwafemi Mistourath, Gómez Paula, Ruiz-Ripa Laura et al. (2019) — Animals : an open access journal from MDPI
An Exploratory Descriptive Study of Antimicrobial Resistance Patterns of Staphylococcus Spp. Isolated from Horses Presented at a Veterinary Teaching Hospital.
Oguttu James Wabwire, Qekwana Daniel Nenene, Odoi Agricola (2017) — BMC veterinary research
Detection and genetic characterisation of vanA-containing Enterococcus strains in healthy Lusitano horses.
Moura I, Radhouani H, Torres C et al. (2010) — Equine veterinary journal
Understanding antimicrobial use by equine owners in Wales: Using cross-sectional survey and semi-structured interviews.
Stuart Rebekah B, Miles-Farrier Fleur, Bard Alison M et al. (2026) — Equine veterinary journal
A review of current and potential applications of macroalgae to equine veterinary science.
Warren P, Mc Crudden D, O'Reilly S et al. (2026) — Journal of equine veterinary science
Use of a point prevalence survey to measure antimicrobial use and antimicrobial resistance in equine veterinary hospitals.
Leus E K, Collins N, Gruyaert M et al. (2026) — Equine veterinary journal
Antimicrobial prescribing and antimicrobial resistance surveillance in equine practice.
Wilson Amie, Mair Tim, Williams Nicola et al. (2023) — Equine veterinary journal
Ceftiofur use and antimicrobial stewardship in the horse.
Ryan Clare A, McNeal Christina D, Credille Brenton C (2023) — Equine veterinary journal
Comparison of approaches for source attribution of ESBL-producing Escherichia coli in Germany.
Perestrelo Sara, Correia Carreira Guido, Valentin Lars et al. (2022) — PloS one
Antimicrobial Effects of Equine Platelet Lysate.
Gordon Julie, Álvarez-Narváez Sonsiray, Peroni John F (2021) — Frontiers in veterinary science
Use of in vitro assays to identify antibiotics that are cytotoxic to normal equine chondrocytes and synovial cells.
Pezzanite Lynn, Chow Lyndah, Piquini Gabriella et al. (2021) — Equine veterinary journal
Show 3 more references
Antimicrobial Resistance in Horses.
Steinman Amir, Navon-Venezia Shiri (2020) — Animals : an open access journal from MDPI
Factors influencing the behaviour and perceptions of Australian veterinarians towards antibiotic use and antimicrobial resistance.
Norris Jacqueline M, Zhuo Annie, Govendir Merran et al. (2019) — PloS one
Use of large-scale veterinary data for the investigation of antimicrobial prescribing practices in equine medicine.
Welsh C E, Parkin T D H, Marshall J F (2017) — Equine veterinary journal