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Topic:Microbiology
Microbiology and horses explores the interactions between microorganisms and equine hosts, focusing on the role of bacteria, viruses, fungi, and other microbes in horse health and disease. This field examines the microbial flora present in various equine environments, including the gastrointestinal tract, skin, and respiratory system, and investigates how these microorganisms influence equine physiology and pathology. Research in this area includes studies on microbial infections that affect horses, the development of antimicrobial resistance, and the impact of probiotics and prebiotics on equine health. This page compiles peer-reviewed research studies and scholarly articles that investigate the diversity, dynamics, and implications of microbial communities in horses, as well as the strategies for managing microbial-related diseases.
Exhaled breath condensate in horses: a first microbiological insight. Exhaled breath condensate (EBC) is a non-invasive method for obtaining samples reflecting the airway lining fluid; however, its microbiological composition remains poorly characterized. Objective: To perform an exploratory microbiological comparison of EBC in clinically healthy horses maintained under different environmental conditions. Methods: An observational study included 30 mares equally distributed into two groups: horses housed in stalls (Racetrack group) and horses maintained under pasture conditions (Farm group). EBC samples were collected using a validated device developed by the re...
Identification and phylogenetic analysis of Mannheimia haemolytica isolated from nasal samples of horses. The Mannheimia genus, which is part of the upper respiratory tract microbiota, harbours species that have the potential to cause progressive infections, such as haemorrhagic septicaemia and enzootic pneumonia, when the host immune system is suppressed. Among these species, Mannheimia haemolytica is considered the most pathogenic, and horses can be a host for this agent. This study aimed to investigate the occurrence of Mannheimia haemolytica in horses with and without respiratory clinical signs and to assess the potential pathogenic significance of isolates recovered from animals through serot...
Serum physiology, fecal microbiota, and metabolome signatures associated with perinatal stage transitions in Mongolian mares. Lactation is a critical reproductive trait that influences offspring survival and livestock productivity in equine production. Characterizing physiological transitions during the perinatal period can improve our understanding of how mares adapt to late gestation, parturition, and early lactation. However, in horses-a typical monogastric herbivore with unique digestive characteristics-the associations between gut microbiota and perinatal physiological adaptation, as well as related stage-associated microbial and metabolic features, remain largely uncharacterized. Unassigned: In this study, para...
Evidence-based interpretation of uterine cultures in mares: Linking bacterial growth patterns to endometrial inflammation. We evaluated uterine bacterial growth patterns and their association with endometrial inflammation (EI) in equine samples collected using uterine swabs (US) or low-volume uterine lavage (UL). A database including 1,545 US and 2,066 UL with cytological and bacteriological results was retrospectively analysed. Endometrial inflammation was defined as ≥2 polymorphonuclear cells per high-power field, and bacterial culture was considered positive when aerobic growth occurred within 48 h, with the number of bacterial isolates per sample recorded (0, 1, 2, or ≥3). Data were analysed using generali...
Effect of sample storage on pH-value in equine faeces. Measurements of pH-value in equine faeces are often performed in studies on nutrition and health in horses, but a standard protocol for it is lacking despite the knowledge that different sample handling may affect the pH-value. Sample handling prior to pH-measurement is often determined by practical settings and has been reported to vary in published studies within the area. The purpose of the current study was therefore to investigate the influence of different combinations of storage time and temperature on the pH-value in equine faecal samples in comparison to immediate pH-measurement at de...
Isolation of Moraxella spp. strains in horses. Two species of Moraxella were isolated from swabs obtained from two symptomatic horses suffering from conjunctivitis and rhinitis. The isolates were identified via MALDI-TOF as Moraxella osloensis and Moraxella equi respectively, with a good genus identification and a probable species identification score. The first one was also confirmed by BLAST sequence analysis with a high homology (99%). Antimicrobial susceptibility testing obtained by minimum inhibitory concentration method showed that the two isolates were sensitive to all the tested molecules. The therapeutic protocols applied had an e...
Microbiological, Molecular Diagnosis and Antimicrobial Resistance of Bordetella bronchiseptica in the Equine Reproductive Tract in Brazil. The genus Bordetella comprises 16 species of aerobic Gram-negative bacteria, with the most notable being B. pertussis, B. parapertussis and B. bronchiseptica. The latter stands out for its ability to infect various hosts, causing both respiratory and reproductive issues, such as endometritis and infertility in mares. These infections impair reproductive efficiency and facilitate the spread of the pathogen among susceptible animals. Objective: The present study aimed to report the isolation and molecular diagnosis of B. bronchiseptica associated with endometritis and infertility in mares in Bra...
Challenges for interpreting results of antimicrobial susceptibility testing for treating infections of foals with Rhodococcus equi. Rhodococcus equi is a facultative intracellular pathogen and a major cause of pneumonia in foals worldwide. The standard treatment for affected foals is a combination of a macrolide with rifampicin. The widespread use of this combination has led to the emergence of multidrug-resistant (MDR) strains of R. equi. Consequently, antimicrobial susceptibility testing is essential for guiding treatment of rhodococcal pneumonia. Unfortunately, clinical breakpoints for macrolides and other antimicrobials against R. equi for foals are lacking, thereby complicating clinical interpretation of in vitro resu...
Guttural pouch tympany or empyema in 38 ٍStraight Egyptian Arabian foals: clinical presentation, diagnostic features and outcome. As a breed, Straight Egyptian Arabian horses are susceptible to many disorders that mostly affect the head, such as guttural pouch (GP) tympany and empyema. This retrospective study evaluated the findings of clinical examination, ultrasonography, endoscopy, laboratory analyses and outcome of treatment of 38 Straight Egyptian Arabian foals with GP tympany and empyema. Methods: Data from medical records of foals diagnosed with GP tympany or empyema over a 2-year period (2024-2025) were reviewed. Foals with verified GP tympany or empyema who had complete medical records and had not previously rec...
From Diet to Disease: The Role of the Gut Microbiome and Microbial Metabolites in Horses. The equine gastrointestinal microbiome plays an essential role in digestion, energy metabolism, immune regulation, and maintenance of intestinal homeostasis. Increasing evidence suggests that microbial-derived metabolites provide a functional link between diet, the microbiome, and host physiology. This narrative review summarizes current knowledge on how dietary factors, including structural carbohydrates, non-structural carbohydrates, protein, and lipids, influence microbial function and metabolite production in horses. Relevant publications available up to June 2026 were identified through s...
Correlation between microbial communities, metabolites, and bioactivities in fermented mare’s milk revealed by metagenomics and metabolomics. Koumiss exhibits various functional properties, including antioxidant, hypoglycemic, and antihypertensive effects; however, natural fermentation is characterized by an uncontrollable microbial community structure, significant fluctuations in product quality, and a lack of specialized fermentation agents. The mechanisms underlying the links between microbial communities, functional metabolites, and bioactivity in natural and inoculated fermentation systems remain unclear. Therefore, this study employed bioactivity assays, metagenomics, and non-targeted metabolomics to systematically analyze dif...
Administration of the Postbiotic Substance 412 to Slovak Warm-Blooded Horses: A Pilot Experiment. Antimicrobial proteinaceous postbiotic substances (PS) and/or bacteriocins can beneficially influence animal health, as previously shown with enterocins from non-autochthonous enterococcal strains. Therefore, the effectiveness of PS 412, produced by our beneficial autochthonous strain EF 412, was assessed in horses. In the pilot experiment, PS 412 was administered to 12 horses of various ages and breeds for 21 days via a small feed ball. Sampling was performed on days 0/1, 21, and 42 (after a 3-week cessation of PS 412). The horses served as their own controls. Although the number of horses w...
Cold Atmospheric Plasma-Aerosol Treatment of Equine Antibiotic-Resistant Wound Infection: A Preliminary Case Series. Wound infections are common sequelae of wound treatment in horses. Secondary bacterial colonization with antimicrobial resistant microorganisms is of particular concern and is of crucial importance regarding the "One Health Concept". Due to frequent antimicrobial resistance (AMR), conventional treatments often involve determining resistance and sensitivity using time-consuming antibiograms. Infections with multi-resistant pathogens are especially challenging. This case series presents studies of four horses evaluating the efficacy of Cold Atmospheric Plasma-Aerosol (CAP-A) as a standalone trea...
Antimicrobial effects of equine regenerative medicine products: A systematic review and meta-analysis of in vitro and in vivo studies. Equine regenerative medicine products involving platelet-rich plasma (PRP), mesenchymal stromal cells (MSCs), and their derivatives are increasingly explored for antimicrobial and therapeutic roles, but their efficacy and between-study variability remain unclear. Objective: To systematically review and meta-analyse in vitro and in vivo evidence on antimicrobial effects of equine regenerative medicine products and to evaluate their efficacy against key pathogens. Methods: Systematic review and meta-analysis: METHODS: We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses...
Intrauterine ozone therapy reduces bacterial load in mares with mixed bacterial endometritis: a longitudinal study. Mixed bacterial endometritis poses a therapeutic challenge in mares due to the coexistence of multiple pathogens with divergent antimicrobial susceptibility profiles. This study evaluated the effects of intrauterine ozone insufflation on uterine bacterial load and endometrial inflammatory response in mares with naturally acquired mixed bacterial endometritis. Fifteen mares with mixed bacterial infection were allocated to two treatment groups: a pathological control group receiving pure medical oxygen insufflation (PC; n = 6) and an ozone-treated group receiving 42 µg/mL ozone for three c...
Bacteremia in horses undergoing routine dental prophylaxis: Before, during, and after the procedure. Transient bacteremia after dental procedures is well-documented in the literature, but the prevalence and clinical significance in horses remains largely unexplored. Objective: To assess whether routine dental prophylaxis in clinically healthy horses is associated with detection of bacteria in blood, using culture and 16S rDNA sequencing. Our central hypothesis is that a percentage of horses would demonstrate detectable but transient bacteremia in the immediate post-procedural period following dental prophylaxis. Methods: Prospective, observational study. Methods: Venous blood samples from 20 ...
Tick-borne pathogens in a nature reserve area in the Netherlands: serological and molecular assessments in large herbivores and Ixodes ricinus ticks. Ticks are vectors of a wide range of pathogens, relevant to both veterinary and public health. Although tick surveillance is frequently conducted in the Netherlands, data on tick-borne pathogens in free-living herbivores remains limited, leaving the impact of these pathogens on animal health poorly understood. This study aimed to characterise tick species and determine seroprevalence and infection prevalence of selected tick-borne pathogens in large herbivores at the Oostvaardersplassen nature reserve and questing ticks collected in the area. Between September 2023 and December 2024, blood was...
The Effects of Cysteamine Zinc Supplementation on Blood Hormones, Intestinal Flora, and Metabolites in Lactating Mares. This study aimed to investigate the effects of cysteamine zinc (CS-Zn) supplementation on blood biochemical indices, blood hormones, fecal fermentation, fecal microbial diversity, and blood metabolites in lactating mares. Blood samples were collected via jugular venipuncture, and fecal samples were collected via rectal sampling before morning tethering on days 30, 60, and 90 of the trial. Fecal samples were analyzed for volatile fatty acids (VFAs) and microbial diversity, while changes in blood biochemical indices, blood hormones, and blood non-targeted metabolomics were also analyzed. The res...
Differential shaping of equine gut microbiota structure and function by breed and feeding regimen. The gut microbiota plays an essential role in host energy metabolism and immune function. Horses are non-ruminant herbivores that rely heavily on hindgut microbial fermentation to meet their energy requirements. However, the relative contributions of host genetic background (breed) and environmental factors (feeding regimen and geographical location) to shaping the equine gut microbiota remain poorly understood. Unassigned: In this study, 16S rRNA gene sequencing and functional prediction analysis were performed on 139 equine fecal samples to systematically investigate the differential effects...
Clinical and microbiota alterations in performance horses undergoing long-distance transport. Transport-associated pneumonia contributes substantially to morbidity, impaired welfare, and economic loss in high-performance horses and may be associated with alterations in the respiratory microbiota. Objective: Examine the effect of long-distance transport on the respiratory microbiota and correlate changes in microbiota diversity and composition with systemic and airway inflammation. Methods: Seventeen client-owned performance horses transported from New England to Florida under optimized trailering conditions, and 12 non-traveling horses. Methods: Physical examination, blood testing, nas...
Efficacy of Therapeutic UVC Irradiation in Reducing Bacterial Load in Microbial Keratitis: A Retrospective Clinical Study in Veterinary Patients. To evaluate the immediate effect of therapeutic ultraviolet-C (UVC) irradiation on corneal bacterial load in veterinary patients with microbial keratitis (MK), using a retrospective analysis of clinical data collected at a UK referral ophthalmology hospital. Methods: Client-owned dogs, horses, and cats presented to a referral ophthalmology clinic with MK in 2025. Methods: Clinical records from MK cases were reviewed. For each case, paired corneal swabs were obtained immediately before and immediately after UVC irradiation with a commercially available 265 nm device (PhotonUVC). Treatment con...
A new single-antigen serological test accurately detects horses infected with Streptococcus equi subsp equi. To develop an accurate serological test for detecting horses infected with Streptococcus equi subsp equi (SEE). Unassigned: The study was designed as a prospective experiment. First, 89 proteins either expressed on the surface or secreted by SEE were cloned, expressed in a cell-free culture system, and printed onto a microarray. Microarrays were probed with serum from 30 horses with strangles, 30 horses with no history of infection or immunization against SEE, and 18 horses infected with Streptococcus equi subsp zooepidemicus (SEZ); serum samples were collected between 2020 and 2021 from Texas...
A Comprehensive Review of the Equine Gut Microbiome in Health and Disease. Molecular microbiology has revolutionized our understanding of the complex host-associated microbiomes required for normative development and physiology. Horses and other members of the family are particularly reliant on the early maturation and lifelong maintenance of an unusually rich hindgut microbiome for optimal digestion and overall health and performance. Research on the equine gut microbiome has accelerated in the past several years, necessitating a renewed appraisal of the field. The present work is a comprehensive and critical review of the literature regarding the bacterial gastroi...
Antibiofilm action of ozonated sunflower oil against bacteria isolated from the uterus of mares susceptible to endometritis. This study aimed to characterize the antibiofilm action of ozone-enriched sunflower oil (O) against pathogens associated with endometritis in mares. Initially, samples from 41 mares with a history of subfertility were stored in BHI broth and 0.9% NaCl solution. The samples underwent microbial culture, identification, and sensitivity testing at LABRAPE-UFRPE, Brazil. Biofilm production was evaluated by the crystal violet method. Subsequently, biofilm-forming bacteria were subjected to the action of different concentrations of ozonated sunflower oil. Of the 21 isolates tested for biofilm produc...
Rapid bacterial community profiling of equine faecal, skin, milk and saliva samples using Oxford Nanopore long-read 16S rRNA amplicon sequencing. The composition of the equine gut microbiome is associated with many aspects of gastrointestinal, respiratory and musculoskeletal health that have been reported in the horse. Scientific studies exploring the microbiome non-intestinal ecological niches in or on horses are lacking. The clinical use of bacterial community profiling in horses is currently limited by cost and by slow analytical workflows. Most equine microbiome studies have relied on 16S rRNA amplicon sequencing of bacterial DNA, using high-throughput short-read sequencing technologies. This is often provided by an external servic...
Tick-borne bacterial and protozoal pathogens in horses in Austria – A cross-sectional study on current and past infections and potential risk factors. Tick-borne bacterial and protozoal pathogens are a major threat to equine health worldwide. In Austria, studies on pathogens such as piroplasms, Anaplasma phagocytophilum and Borrelia spp. in horses are scarce and do not cover the countrywide horse population. To address this, blood samples from horses without prior record of infection with tick-borne pathogens (n = 588) were tested for the presence of Theileria equi, Babesia caballi or A. phagocytophilum DNA by PCR and for specific antibodies against these pathogens and Borrelia burgdorferi with commercially available assays. While no DNA of ...
Prevalence of Clostridioides difficile in hospitalized neonatal mare-foal pairs from Alberta and direct comparison of fecal culture with toxin gene detection. is an important pathogen in the feces of adult horses and foals. It can be clinically diagnosed using several testing methods, including culture isolation and, more commonly, direct toxin gene detection from feces using molecular methods. The importance of monitoring shedding in foals or dams during hospitalization remains unclear. The objectives of this study were to determine the prevalence of fecal shedding in mare-foal pairs and to compare detection using isolation and a commercial real-time polymerase chain reaction (qPCR) for toxin A and B genes in feces. Foals and their mares admitte...
Diagnosis of bacteraemia in neonatal foals using 16S rRNA high-throughput sequencing. Sepsis is an important cause of morbidity and mortality in foals. Early diagnosis can improve outcome but is complicated by non-specific clinical signs and delayed confirmation of infection via blood culture. Molecular assays represent a rapid and more sensitive alternative. Objective: To evaluate and compare bacterial load and composition in blood and blood culture media (BCM) of sick and healthy foals using molecular assays and to compare results with traditional bacterial culture. Methods: Cross-sectional observational clinical study. Methods: Thirteen septic foals, 10 sick non-septic and 8...
Inhaled Corticosteroids Influence Pulmonary Microbiota in Severe Equine Asthma. The use of inhaled corticosteroids (ICs) could influence the respiratory microbiota. In animals with asthma it is, however, difficult to separate the immunomodulatory effects of ICs from their indirect effects via improvement of ventilation. Our objective was to determine if ICs alter the pulmonary microbiota independently from their effects on lung function, using a blinded, controlled trial in an experimental model of asthma exacerbation in horses. We treated horses with severe asthma with either bronchodilators alone, or in combination with ICs. Twelve horses in exacerbation received long-a...
Short-term provision of moderate dietary starch alters fecal microbiota but does not exacerbate exercise-induced inflammation in yearling Quarter Horses. Energy-dense feeds commonly provided to equine athletes may be high in starch, which alter gastrointestinal microbiota and could promote systemic inflammation. Objective: To test the hypothesis that exercise-induced inflammation would be greater in horses receiving a starch- versus fiber-based concentrate. Methods: Quarter Horses (mean±SD 16±1mo; 337±30kg) received either a fiber-based control (CON; 7 fillies, 8 geldings) or an isocaloric, isonitrogenous starch concentrate (STARCH; 8 fillies, 7 geldings) for 24d. Fecal metagenomics were evaluated on d0 and 21. Blood inflammatory mediators w...
