Disease transmission in horses

Bacterial diversity in semen from stallions in three European countries evaluated by 16S sequencing

The microbiome plays a significant role in shaping the health and functioning of the systems it inhabits. The seminal microbiome of stallions has implications for the health of the reproductive tract, sperm quality during preservation and antibiotic use in semen extenders. Diverse bacteria are present on the external genital tract and a mix of commensal microorganisms populates various parts of the reproductive tract, influencing the seminal bacterial content. Other sources of bacteria include the environment, semen collection equipment, and personnel. The bacterial load can adversely affect sperm quality and fertility, particularly in artificial insemination, where semen is extended and stored before use. Antibiotics are frequently used to inhibit bacterial growth, but their effectiveness varies depending on the bacterial strains present. The aim of this study was to assess the bacterial diversity in semen from 37 healthy stallions across three European nations (Germany, Portugal, and Sweden) using 16S sequencing. Semen samples were collected from individual stallions at three AI centers; DNA extraction, sequencing, and bioinformatic analysis were performed. Differences in bacterial diversity among the stallions were seen; although bacterial phyla were shared across the regions, differences were observed at the genus level. Climate, husbandry practices, and individual variability likely contribute to these differences. These findings underscore the importance of tailoring antibiotic strategies for semen preservation based on regional bacterial profiles. The study presents a comprehensive approach to understanding the intricacies of the stallion seminal microbiome and its potential implications for reproductive technologies and animal health.

Pseudomonas aeruginosa strains isolated from animal with high virulence genes content and highly sensitive to antimicrobials

OBJECTIVES

P. aeruginosa is one of the most metabolically versatile bacteria having the ability to survive in multiple environments through its accessory genome. An important hallmark of P. aeruginosa is the high level of antibiotic resistance, which often makes eradication difficult and sometimes impossible. Evolutionary forces have led to this bacterium to develop high antimicrobial resistance with a variety of elements contributing to both intrinsic and acquired resistance. The objectives were to genetically and phenotypically characterizer P. aeruginosa strains isolated from companion animals of different species.

METHODS

We characterized a collection of 39 P. aeruginosa strains isolated from infected animals. The genetic characterization was in relation to chromosomal profile by PFGE; content of virulence gene; presence of genomic islands (GIs); genes of the cytotoxins exported by T3SS: exoU, exoS, exoT and exoY; and type IV pili allele. The phenotypic characterization was based on patterns of susceptibility to different antimicrobials.

RESULTS

Each strain had a PFGE profile, a high virulence genes content, and a large accessory genome. However, most of the strains presented high sensitivity to almost all antimicrobials tested, showing no acquired resistance (no β-lactamases). The exception to this lack of resistance was seen with penicillin.

CONCLUSIONS

P. aeruginosa could be a naturally sensitive bacterium to standard antimicrobials but could rapidly develop intrinsic and acquired resistance when the bacterium is exposed to pressure exerted by antibiotics, as observed in hospital settings.

Freezing Stallion Semen-What Do We Need to Focus on for the Future?

Artificial insemination (AI) is used frequently in the breeding of sport horses, apart from Thoroughbreds. Most AIs are carried out with cooled semen rather than frozen semen because of the difficulties in identifying a protocol that is suitable for freezing most ejaculates and the necessity to inseminate close to ovulation because of the short life of the thawed spermatozoa. More widespread use of frozen semen would improve biosecurity, allow greater choice of stallions, and offer more flexibility when managing deliveries of semen to the stud. It would even decrease the amount of antibiotics used in semen extenders, since the volume of frozen semen is smaller than when cooled semen is inseminated. However, there is considerable variability in the cryosurvival of spermatozoa from different stallions, leading to the classification of stallions as good or bad freezers. Improvements could be made at the level of stallion nutrition, the semen collection regimen, the extender, the removal of seminal plasma, and the cooling protocol, among others. Stallion sperm membranes are highly susceptible to lipid peroxidation, but research on antioxidants has failed to identify an additive that would benefit all stallions. In the future, biomarkers for sperm freezability could be used as an aid in identifying suitable ejaculates for cryopreservation.

Strategies to Reduce the Use of Antibiotics in Fresh and Chilled Equine Semen

The study assessed the impact of four equine semen processing techniques on sperm quality and microbial load immediately post-processing and after 48 h of refrigeration. The aim was to explore the potential reduction of prophylactic antibiotic usage in semen extenders. Semen from ten adult stallions was collected and processed under a strict hygiene protocol and divided into four aliquots: Simple Centrifugation with antibiotics (SC+), Simple Centrifugation (SC-), Single-Layer Colloidal Centrifugation (CC-), and Filtration (with SpermFilter®) (F-), all in extenders without antibiotics. Sperm motility, viability, and microbial load on three culture media were assessed. No significant differences were observed in the main in the sperm quality parameters among the four protocols post-processing and at 48 h (p < 0.05 or p < 0.1). Microbial loads in Columbia 5% Sheep Blood Agar and Schaedler vitamin K1 5% Sheep Blood Agar mediums were significantly higher (p < 0.10) for raw semen than for CS+, CC-, and F- post-processing. For Sabouraud Dextrose Agar medium, the microbial load was significantly higher (p < 0.10) in raw semen compared to CS+ and F-. No significant differences (p < 0.10) were found in 48 h chilled samples. Regardless of antibiotic presence, the evaluated processing methods, when combined with rigorous hygiene measures, maintained semen quality and reduced microbial load to the same extent as a traditional protocol using antibiotics.

Strategies for Bacterial Eradication from Human and Animal Semen Samples: Current Options and Future Alternatives

The primary role of semen processing and preservation is to maintain a high proportion of structurally and functionally competent and mature spermatozoa, that may be used for the purposes of artificial reproduction when needed, whilst minimizing any potential causes of sperm deterioration during ex vivo semen handling. Out of a multitude of variables determining the success of sperm preservation, bacterial contamination has been acknowledged with an increased interest because of its often unpredictable and complex effects on semen quality. Whilst antibiotics are usually the most straight-forward option to prevent the bacterial contamination of semen, antimicrobial resistance has become a serious threat requiring widespread attention. As such, besides discussing the consequences of bacteriospermia on the sperm vitality and the risks of antibiotic overuse in andrology, this paper summarizes the currently available evidence on alternative strategies to prevent bacterial contamination of semen prior to, during, and following sperm processing, selection, and preservation. Alternative antibacterial supplements are reviewed, and emphasis is given to modern methods of sperm selection that may be combined by the physical removal of bacteria prior to sperm preservation or by use in assisted reproductive technologies.

Clinical Aspects of Bacterial Distribution and Antibiotic Resistance in the Reproductive System of Equids

Antibiotic administration is a standard therapeutic practice for the treatment of reproductive disorders of equids. This might lead to undesirable microbial imbalance and could favour the acquisition of antibiotic resistance. Therefore, it is imperative for clinicians to understand patterns of antibiotic resistance when considering and developing treatment regimes. Continued engagement of clinicians with novel alternative approaches to treat reproductive infections would be essential in order to address this rising threat within the One Health perspective. The objectives of the present review were to present the bacterial infections in the reproductive system of equids (horses, donkeys), to upraise the literature related to the issue of antibiotic resistance of bacteria causing these infections and to discuss the topic from a clinical perspective. Initially, the review summarised the various infections of the reproductive system of equids (genital system of females, genital system of males, mammary glands) and the causal bacteria, providing relevant information about horses and donkeys. Subsequently, the clinical therapeutics of these infections were presented, taking into account the significance of antibiotic resistance of bacteria as a limiting factor in treating the infections. Finally, approaches to circumvent antibiotic resistance in clinical settings were summarized. It was concluded that awareness regarding antibiotic resistance in equine reproductive medicine would increase, as we would recognise the multifaceted problem of resistance. Actions and initiatives within the One Health approach, minimizing the potential dissemination of resistant strains to humans and to the environment, with specific applications in medicine of equids should be appropriately instituted internationally.

Penicillin and amikacin mixture has bactericidal activity equivalent to gentamicin, tylosin, lincomycin and spectinomycin mixture in equine frozen semen

Neat stallion semen can contain a variety of microorganisms, some of which may impair sperm quality and/or cause infection of the mares' reproductive tract. For this reason, antibiotics are commonly added to semen extenders. A combination of gentamicin, tylosin, lincomycin and spectinomycin (GTLS) has been recommended for use, but there are no reports on the use of this mixture in equine semen extender. Penicillin and amikacin (PA) are safe for preserving sperm quality while effectively controlling bacterial growth in equine cooled stored semen, but data on frozen semen are scarce. Therefore, a bioequivalence study was performed to assess the bactericidal activity of GTLS and PA in equine frozen semen. Nine mature, healthy stallions were used in the study. Split ejaculates were processed using media without antibiotics (Control) or with different antibiotics. For the GTLS group, centrifugation medium and freezing extender were prepared with gentamicin 250 μg/ml, tylosin 50 μg/ml, lincomycin 150 μg/ml and spectinomycin 300 μg/ml. For the PA group, the centrifugation medium was prepared with potassium penicillin G (PPG) 1200 units/ml and the freezing extender was prepared with PPG 1200 units/ml and amikacin 500 μg/ml. Semen processed in extenders without antibiotics had higher (p < .005) bacterial loads throughout all cryopreservation processing steps than semen samples processed using antibiotics. There were no differences in semen bacterial load after centrifugation, 15 and 30 min after final extension, and after thawing between GTLS and PA groups, but PA had faster (p < .05) kill-time kinetics than GTLS. Only minor differences in sperm kinetic parameters were observed among groups. In conclusion, this study demonstrated bioequivalence between GTLS and PA in mitigating end-point bacterial loads. Prudent concentrations of the antibiotic mixtures evaluated in this study can be considered both effective and sperm-safe for equine frozen semen.

Bacterial killing activity and lysozymes: A stable defence mechanism in stallion seminal plasma?

During insemination, bacterial contamination of the ejaculate can lead to reduced sperm quality and transmission of pathogens to the female, thus should be avoided. The semen of a variety of animal taxa possess antimicrobial properties against a wide range of bacterial species through antimicrobial molecules, such as lysozyme, but their variance and the factors influencing it are unknown for most species. In this study, the antibacterial defence (bacterial killing activity (BKA) against Escherichia (E.) coli and Staphylococcus (S.) aureus as well as lysozyme concentration) was studied in seminal fluid from two consecutive ejaculates of 18 stallions. All ejaculates showed BKA against the tested bacteria, which correlated between the two consecutive ejaculates (r_S  = 0.526, p = .025 for E. coli and r_S  = 0.656, p = .003 for S. aureus) and appeared to be stable over the tested period. The lysozyme concentration (LC) showed no significant correlation between the consecutive ejaculates (r_S  = 0.161, p = .681). However, LC had a positive correlation to the ratio of apoptotic spermatozoa within the ejaculates (r_S  = 0.426, p = .019). In contrast to other livestock (e.g., boar, bull), the BKA in stallion semen did not correlate significantly with the age of the animal nor sperm quality characteristics.

Equine Influenza

Horses are the third major mammalian species, along with humans and swine, long known to be subject to acute upper respiratory disease from influenza A virus infection. The viruses responsible are subtype H7N7, which is believed extinct, and H3N8, which circulates worldwide. The equine influenza lineages are clearly divergent from avian influenza lineages of the same subtypes. Their genetic evolution and potential for interspecies transmission, as well as clinical features and epidemiology, are discussed. Equine influenza is spread internationally and vaccination is central to control efforts. The current mechanism of international surveillance and virus strain recommendations for vaccines is described.

Antimicrobial Resistance in Equine Reproduction

Bacteria develop resistance to antibiotics following low-level "background" exposure to antimicrobial agents as well as from exposure at therapeutic levels during treatment for bacterial infections. In this review, we look specifically at antimicrobial resistance (AMR) in the equine reproductive tract and its possible origin, focusing particularly on antibiotics in semen extenders used in preparing semen doses for artificial insemination. Our review of the literature indicated that AMR in the equine uterus and vagina were reported worldwide in the last 20 years, in locations as diverse as Europe, India, and the United States. Bacteria colonizing the mucosa of the reproductive tract are transferred to semen during collection; further contamination of the semen may occur during processing, despite strict attention to hygiene at critical control points. These bacteria compete with spermatozoa for nutrients in the semen extender, producing metabolic byproducts and toxins that have a detrimental effect on sperm quality. Potential pathogens such as Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa may occasionally cause fertility issues in inseminated mares. Antibiotics are added during semen processing, according to legislation, to impede the growth of these microorganisms but may have a detrimental effect on sperm quality, depending on the antimicrobial agent and concentration used. However, this addition of antibiotics is counter to current recommendations on the prudent use of antibiotics, which recommend that antibiotics should be used only for therapeutic purposes and after establishing bacterial sensitivity. There is some evidence of resistance among bacteria found in semen samples. Potential alternatives to the addition of antibiotics are considered, especially physical removal separation of spermatozoa from bacteria. Suggestions for further research with colloid centrifugation are provided.

Development and Application of a Multiplex Real-Time Polymerase Chain Reaction Assay for the Simultaneous Detection of Bacterial Aetiologic Agents Associated With Equine Venereal Diseases

Venereal diseases caused by bacteria are important to the equine industry due to economic losses caused by decline of conception rate in breeding horses. Therefore, identification of infected animals as well as the implementation of appropriate managerial procedures based on accurate diagnosis is critical. In this study, two types of multiplex real-time polymerase chain reaction with high sensitivity and specificity were developed for the simultaneous detection and differentiation of five commonly associated bacterial pathogens of venereal diseases in horses, consisting of Taylorella equigenitalis, Taylorella asinigenitalis, Pseudomonas aeruginosa, Klebsiella pneumoniae and Streptococcus zooepidemicus. The assay was applied to samples collected as part of the surveillance of T.equigenitalis infection in South Korea. Swab samples collected from horses in 2015 were tested. T. equigenitalis and K. pneumoniae was detected in 21 (21.0%) and two (2.0%) samples, respectively. No samples were positive for T. asinigenitalis, P. aeruginosa, and S. zooepidemicus. Application of this assay to an existing surveillance program has allowed for an enhanced surveillance for a wider range of venereal diseases of equine to be implemented in South Korea.

Microbiota of semen from stallions in Sweden identified by MALDI-TOF

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Bacteria isolated from stallion semen vary in number and species found.

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Differences may depend on culture conditions and method of identification.

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64% bacteria in stallion semen were cultured and identified by MALDI-TOF.

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The number of bacteria varied considerably among samples, even from the same stud.

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More information is needed on their effect on sperm quality.

Stallion semen is known to contain environmental bacteria and normal commensals, and in some cases may contain opportunistic pathogens. These bacteria may negatively influence sperm quality during storage before artificial insemination. The bacteria isolated depend on the culture conditions and method of identification; therefore, the aim of this study was to identify as many of the bacteria present in stallion semen as possible by culturing aliquots of semen under a variety of conditions. Eleven semen samples were available: five extended semen samples from one stud together with a sample of the extender, and six raw semen samples from another stud. Aliquots of semen samples were cultured on different agars and under specialized conditions; individual bacterial colonies were identified using Matrix-assisted laser desorption ionization time of flight mass spectrometry. Approximately 55% of the bacteria could be identified, with 20 bacterial taxa being isolated from semen samples from the five stallions on the first stud and 11 taxa from the semen samples from six stallions on the second stud. Staphylococcus spp. were present in all samples, and Micrococcus spp. were present in all of the extended semen samples although they were also isolated from the extender. The number of bacteria in colony forming units per mL varied considerably among samples. Only one microbe known to be associated with equine infertility, Pseudomonas spp., was isolated from three samples, albeit in low numbers. In conclusion, bacterial culture followed by MALDI-TOF does not identify all bacteria present in stallion semen samples. In-depth knowledge of which microbes are likely to be present is useful in determining their effects on sperm quality and, where appropriate, developing protocols for effectively controlling microbial growth.

Validation of an Easy Handling Sample Preparation and Triplex Real Time PCR for Rapid Detection of T. equigenitalis and Other Organisms Associated with Endometritis in Mares

Isolation and identification of Taylorella equigenitalis, the causative agent of contagious equine metritis, by bacteriology is laborious and does not permit differentiation from the other member of the genus, Taylorella asinigenitalis. Moreover, other organisms such as Klebsiella pneumoniae and Pseudomonas aeruginosa can also cause endometritis in mares and warrant diagnostic detection. Our objectives were to develop a rapid preparation method for field swab samples and to validate this protocol using new multiplex real-time polymerase chain reaction (rtPCR) detection tools for identification of these four pathogens. The complete analytical process from sample preparation to PCR analysis was then evaluated against bacteriology, the World Organisation for Health's (OIE) gold standard method for T. equigenitalis and commonly used for the other three pathogens. The diagnostic sensitivity and specificity of this method, which used direct lysis and a multiplex rtPCR, were 100% and >92%, respectively. This study provided a simple-to-use method for prebreeding screening of mares and stallions.

Update on Seminal Vesiculitis in Stallions

Seminal vesiculitis in stallions reduces fertility and is often underdiagnosed. The most common cause is infection of seminal vesicles by bacteria capable of forming biofilms and a propensity for tissue persistence, for example, Pseudomonas aeruginosa. Achieving a clinical cure is challenging because of a high rate of recurrence. Systemic antibiotic therapy does not reach adequate therapeutic concentrations within the seminal vesicles; one alternative is endoscopy-guided, local antibiotic infusion into the gland lumen, with or without concurrent systemic antibiotics. Current diagnostic and therapeutic strategies for seminal vesiculitis are less than fully satisfactory, and several studies have been conducted to improve them. This review covers traditional and newer concepts regarding seminal vesiculitis, including diagnostic and treatment methods, management of stallions with this disorder, and authors' experience with clinical cases.

Metagenomic analysis of bacteria in stallion semen

Bacteria colonize stallion semen during collection and processing which may cause disease in inseminated females or negatively affect sperm quality during storage prior to insemination. Antibiotics are added to semen extenders to control the growth of these bacteria but may induce antimicrobial resistance. Research into alternatives to antibiotics for this purpose requires knowledge of which bacteria are present in semen. Not all bacteria in semen, however, can be identified by conventional microbiological techniques. The objectives of the study were to: i) determine which bacteria are present in stallion semen using metagenomics; and ii) investigate individual differences in bacterial content in semen from all stallions on one premises. Bacterial DNA was extracted from ejaculates from seven stallions (one ejaculate per stallion) and bacteria were identified using 16S sequencing. In total, 83 bacterial genera were identified, varying from 25 to 52 among different individuals. There was a negative correlation (r = -0.81212; P <  0.05) between the presence of Treponema spp. and Advenella spp. In conclusion, most of the bacteria present in stallion semen could be identified to genus level by 16S sequencing even when present at a low frequency. This method of identification may help to clarify individual variation in bacterial content and its potential effects on fertility.

Fractionated semen collection as a tool to rescue fertility in stallions with seminal vesiculitis

Treatments for seminal vesiculitis have poor outcomes in stallions; thus, the development of alternative strategies is warranted. This study aimed to evaluate fractionated semen collection as a method to restore the fertility of stallions diagnosed with seminal vesiculitis. Eighteen ejaculates from six stallions (three ejaculates/stallion) diagnosed with seminal vesiculitis were harvested in fractions, as follows: Fraction A (FA), the first two jets; Fraction B (FB), the third and fourth jets; and Fraction C (FC), the fifth and remaining jets of the ejaculate. All fractions were subject to standard semen evaluations that were performed in addition to cytology and bacterial aerobic cultures. Fractions were extended and cooled to 5 °C. As a proof of concept, 20 mares (48 estrous cycles, ∼8 cycles/stallion) were bred with 1 billion sperm from FA (cooled at 5 °C for 24 h). In our study, FA had negative bacterial cultures, absent macroscopic or microscopic abnormalities; FB had positive bacterial cultures in two stallions and presence of polymorphonuclear neutrophils (PMNs) in all samples, but with no macroscopic abnormalities; and FC had positive bacterial cultures, purulent appearance, and the presence of degenerated PMNs, just as noted in the whole semen. Overall, post-cooling sperm motility results were superior (P < 0.05) for FA in comparison with FB and FC. First cycle pregnancy rates using FA varied from 66% to 86%. None of the non-pregnant mares developed endometritis. In conclusion, fractionated semen collection can be used to obtain semen free of contamination and to achieve satisfactory pregnancy rates from stallions with seminal vesiculitis.

Equine Herpesvirus-I Infection in Horses: Recent Updates on its Pathogenicity, Vaccination, and Preventive Management Strategies

Equine herpesvirus-1 (EHV-1) is one of the most common and ubiquitous viral pathogens infecting equines, particularly horses worldwide. The EHV-1 is known to induce not only humoral but also cellular immune responses in horses. Respiratory distress, abortion in pregnant mares, neurological disorders, and neonatal foal deaths represent EHV-1 infection. Despite the limited success of inactivated, subunit, live, and DNA vaccines, over the past few decades, vaccination remains the prime preventive option to combat EHV-1 infection in horses. However, current vaccines lack the potentiality to protect the neurological form of infections in horses. There is desperate necessity to search effectual EHV-1 vaccines that may stimulate not only mucosal and systemic cellular immunity but also humoral immunity in the horses. This review highlights the state of knowledge regarding EHV-1 biology, EHV-1 pathogenesis, and disparate vaccines studied in the past to prevent EHV-1 infection. The review also underlines the best management strategies which certainly need to be adopted by veterinarians in order to avoid and prevent EHV-1 infection and outbreak in horses in the future.

Does semen quality change after local treatment of seminal vesiculitis in stallions?

Inflammation of the seminal vesicle interferes with fertility and is a persistent problem that is difficult to treat. The aim of this study was to evaluate the semen quality of 5 stallions with seminal vesiculitis before and after local treatment. All stallions were endoscopically treated for seminal vesiculitis during 10 consecutive days. The glandular lumen was accessed and flushed with a Ringer Lactate solution prior to antibiotic infusion. The antibiotic was selected based on the antibiogram from bacterial culture of samples previously collected from the seminal vesicles. The kinetic parameters (total motility - TM; progressive motility - PM; and rapid sperm - RAP), plasma membrane integrity (PMI), percentage of leukocyte (LEUK) and colony forming units (CFU) of fresh semen samples were evaluated. Additionally, nitric oxide (NO) content in seminal plasma was measured. All parameters were assessed before (T0), one week after treatment (T1) and one month after therapy (T2). The sperm kinetics and plasma membrane integrity showed an improvement in T1 that didn't last until T2. Percentage of leukocytes and CFU decreased on fresh semen and NO decreased on seminal plasma at T1 but were similar between T0 and T2. The results demonstrate that one week (T1) of local treatment leads to an improvement in sperm quality. However, this was not maintained one month (T2) after therapy, as seminal parameters at this time are similar to the pre-treatment values (T0), indicating the recurrence of the disease one month after therapy.

Temporal efficacy of antimicrobials against aerobic bacteria isolated from equine endometritis: an Italian retrospective analysis (2010-2017)

This study aimed to describe bacteria isolated from the reproductive tract of mares and to identify changes in antimicrobial susceptibility patterns to those antibiotics commonly used for the treatment of equine endometritis. A total of 4122 equine uterine swabs were collected from mares suffering from reproductive tract disorders in the period 2010-2017. Aerobic culture and antimicrobial susceptibility testing using agar disc diffusion were performed on each sample. Aerobic bacteria were isolated from 3171 of 4122 (76.9 per cent) samples. The most frequently isolated microorganisms were Escherichia coli (885/3171, 27.9 per cent) and Streptococcus equi subspecies zooepidemicus (791/3171, 24.9 per cent), confirming previous findings from the literature. Antimicrobial susceptibility patterns of E coli, S equi subspecies zooepidemicus and Klebsiella pneumoniae changed over time. A statistically significant decrease in antimicrobial efficacy of cefquinome against E coli was observed over the years, as well as of ampicillin, cefquinome and penicillin against S equi subspecies zooepidemicus The high frequency of resistant bacteria isolated in the present work proceeds in the same way as indicated by surveillance data on the huge antibiotic use in Italy. As a result, testing and monitoring programmes of antimicrobial efficacy are crucial to consciously using antibiotics and preserving their effectiveness both for veterinary and human medicine.

In vitro antimicrobial susceptibility of equine clinical isolates from France, 2006-2016

OBJECTIVES

This study aimed to analyse antimicrobial susceptibility evolution of equine pathogens isolated from clinical samples from 2006-2016.

METHODS

A collection of 25 813 bacterial isolates was studied, clustered according to their origins (respiratory tract, cutaneous, genital and other), and analysed for their antimicrobial susceptibility using the disk diffusion method.

RESULTS

The most frequently isolated pathogens were group C Streptococci (27.6%), Escherichia coli (20.0%), Staphylococcus aureus (7.8%), Pseudomonas aeruginosa (4.0%), Enterobacter spp. (3.4%), Klebsiella pneumoniae (2.4%), and Rhodococcus equi (1.8%). Of the isolates, 9512 were from respiratory samples (36.8%), 7689 from genital origin (29.8%), and 4083 from cutaneous samples (15.8%). Over the 11-year period, the frequency of multidrug-resistant (MDR) strains fluctuated between 6.4-20.4% for group C Streptococci and 17-37.7% for Klebsiella pneumoniae. From 2006-2009, 24.5-43.0% of Staphylococcus aureus isolates were MDR; after 2009 the level did not exceeded 27.6%. For Escherichia coli and Enterobacter spp., these levels were mostly >30.0% until 2012, but significantly decreased thereafter (22.5-26.3%).

CONCLUSIONS

This study is the first large-scale analysis of equine pathogens, by the number of samples and duration of study. The results showed high levels of MDR strains and the need to support veterinary antimicrobial stewardship to encourage proper use of antibiotics.

Effect of presence or absence of antibiotics and use of modified single layer centrifugation on bacteria in pony stallion semen

Bacteria contaminate semen during collection and handling. The objective of this study was to identify the bacteria in pony stallion semen, the effects of antibiotics included in commercial semen extenders (lincomycin and spectinomycin) and the effect of modified single layer centrifugation (MSLC), on bacterial load. Ejaculates from six pony stallions, 3 ejaculates per animal, were extended in EquiPlus extender either with or without antibiotics. Aliquots were processed by MSLC to form four treatment groups: control and MSLC with antibiotics (CA and SA, respectively) and control and MSLC without antibiotics (CW and SW, respectively). Bacteriological examinations were carried out within 2 hr. Thirty-one species of bacteria were isolated from one or more ejaculates, with Corynebacterium spp. being the most frequently detected. Corynebacterium spp. were present in all ejaculates. The MSLC resulted in a significantly lower total bacterial count than controls (CA vs. SA, p < 0.001; CW vs. SW, p < 0.0001).

Population genomics of hypervirulent Klebsiella pneumoniae clonal-group 23 reveals early emergence and rapid global dissemination

Severe liver abscess infections caused by hypervirulent clonal-group CG23 Klebsiella pneumoniae have been increasingly reported since the mid-1980s. Strains typically possess several virulence factors including an integrative, conjugative element ICEKp encoding the siderophore yersiniabactin and genotoxin colibactin. Here we investigate CG23's evolutionary history, showing several deep-branching sublineages associated with distinct ICEKp acquisitions. Over 80% of liver abscess isolates belong to sublineage CG23-I, which emerged in ~1928 following acquisition of ICEKp10 (encoding yersiniabactin and colibactin), and then disseminated globally within the human population. CG23-I's distinguishing feature is the colibactin synthesis locus, which reportedly promotes gut colonisation and metastatic infection in murine models. These data show circulation of CG23 K. pneumoniae decades before the liver abscess epidemic was first recognised, and provide a framework for future epidemiological and experimental studies of hypervirulent K. pneumoniae. To support such studies we present an open access, completely sequenced CG23-I human liver abscess isolate, SGH10.

Evolutionary Analysis Provides Insight Into the Origin and Adaptation of HCV

Hepatitis C virus (HCV) belongs to the Hepacivirus genus and is genetically heterogeneous, with seven major genotypes further divided into several recognized subtypes. HCV origin was previously dated in a range between ∼200 and 1000 years ago. Hepaciviruses have been identified in several domestic and wild mammals, the largest viral diversity being observed in bats and rodents. The closest relatives of HCV were found in horses/donkeys (equine hepaciviruses, EHV). However, the origin of HCV as a human pathogen is still an unsolved puzzle. Using a selection-informed evolutionary model, we show that the common ancestor of extant HCV genotypes existed at least 3000 years ago (CI: 3192–5221 years ago), with the oldest genotypes being endemic to Asia. EHV originated around 1100 CE (CI: 291–1640 CE). These time estimates exclude that EHV transmission was mainly sustained by widespread veterinary practices and suggest that HCV originated from a single zoonotic event with subsequent diversification in human populations. We also describe a number of biologically important sites in the major HCV genotypes that have been positively selected and indicate that drug resistance-associated variants are significantly enriched at positively selected sites. HCV exploits several cell-surface molecules for cell entry, but only two of these (CD81 and OCLN) determine the species-specificity of infection. Herein evolutionary analyses do not support a long-standing association between primates and hepaciviruses, and signals of positive selection at CD81 were only observed in Chiroptera. No evidence of selection was detected for OCLN in any mammalian order. These results shed light on the origin of HCV and provide a catalog of candidate genetic modulators of HCV phenotypic diversity.

How does the microbial load affect the quality of equine cool-stored semen?

Contaminating bacteria present in stallion ejaculates may compromise sperm quality during storage. Different procedures have been used to reduce the load of microorganisms in semen and avoid bacterial growth during storage. The aims of this study were: 1) to evaluate different techniques to eliminate bacteria in semen 2) to study the relationship between total microflora load (TML) and ROS production; and 3) to determine if TML affects the functionality of cool-stored sperm. Ejaculates from 11 stallions were split and processed in 3 ways: A. extended semen; B. conventional centrifuged semen, and C. Single layer centrifugation through Androcoll-E (SLC). All samples were preserved in INRA 96 at 5 °C for 72 h. Aliquots from native semen and from different treatments were taken for bacteriological analysis at T0, T24, T48 and T72h of storage and Total microbial load (TML: CFU (colony-forming units/ml) was calculated. The ROS production (dichlorodihydrofluorescein diacetate for H₂O₂, dihydroethidium for superoxide anion and CellROX deep red for total ROS), viability (YO-PRO-1-Ethidium) and lipid peroxidation (BODIPY-C11) were assessed by flow cytometry, and motility by CASA. The bacteria isolated were Corynebacterium spp, Arcanobacterium spp, Bacillus spp, Dermobacter, Staphylococcus spp, Streptococcus spp, Penicilium spp. TML of semen showed correlations with live sperm (r: -0.771), dead sperm (r: 0.580), H₂O₂ production (r: 0.740), and total ROS production (CellROX (+)) (r: -0.607), Total motility (r: 0.587), Progressive motility (r: -0.566), VCL (r: -0.664), VSL (r: -0,569), VAP (r: -0.534) (p ≤ 0.05). SLC removed 99.34% of the microbial load, which was assicated with a significanlty reduced H₂O₂ production (p ≤ 0.05). However, only samples treated with Androcoll-E had a higher total ROS production (CellROX +) (p ≤ 0.05). These results suggest that CellROX stain probably identifies superoxide production rather than H₂O₂ and this higher superoxide production may reflect an intense sperm functionality. The bacterial load increased the production of H₂O₂ in cool-stored semen which was associated with lower tolerance to refrigeration. SLC was the sperm processing technique that was most efficient at removing bacteria, reducing H₂O₂ production and selecting the most functional sperm.

Epidemiological investigation and analysis of the NS5B gene and protein variability of non-primate hepacivirus in several horse cohorts in Rio de Janeiro state, Brazil

Among the hepacivirus species recently described, the non-primate hepacivirus/hepacivirus A found in horses and donkeys is closely related to the human hepatitis C virus (HCV). Therefore, the equine is an attractive surrogate large animal model for the study of HCV therapy, pathogenesis and prophylaxis. Despite global efforts, epidemiological and genetic studies have not elucidated the risk factors, virus distribution or genetic variability of the hepacivirus A, which are also important issues for the equine welfare. Little information about this background scenery is available in Brazil. The aims of this study were to investigate potential risk factors associated with hepacivirus A infection among different horse cohorts throughout the state of Rio de Janeiro and to evaluate the diversity of the viral NS5B gene and protein. Hepacivirus A RNA was detected in horse cohorts from all geographical mesoregions, independent of horse activity or breed investigated. Statewide prevalence ranged from 4.0% to 27.5%. Potential risk factors such as geographical location and age of female horses were significantly associated with the presence of virus RNA. Phylogenetic analysis revealed the circulation of subtype 2 in all mesoregions. NS5B gene sequences clustered according to geographical origin, while the NS5B fragments did not allow discriminant analysis. The predicted NS5B protein showed marked conservation, especially in the thumb domain. In conclusion, the higher frequency of hepacivirus A RNA detection in horses bred for reproduction purposes as well as in young females suggests a direct link between reproduction practices and the virus's spread. Additional studies are necessary to understand the distribution of this genetically conserved hepacivirus.

Amiata Donkey Milk Chain: Animal Health Evaluation and Milk Quality

This study presents an investigation of Amiata donkey health and quality of milk for human consumption. Thirty-one lactating dairy jennies were examined. The following samples were collected: faecal samples from the rectum of animals for parasitological examination; cervical swabs for the detection of bacteria causing reproductive disorders; and blood samples for serological diagnosis of main zoonotic (Brucella spp., Leptospira spp.) and donkey abortion agents (Brucella spp., Leptospira spp., Salmonella abortus equi, Equine viral arterithis virus, Equine herpesvirus type 1). In addition, individual milk samples were collected and analysed for mastitis-causing pathogens and milk quality. Regarding animal health, we detected a high prevalence of strongyle parasites in donkeys. It is very important to tackle parasitic diseases correctly. Selective control programmes are preferable in order to reduce anthelmintic drug use. For dairy donkeys, withdrawal periods from anthelmintic drugs need to be carefully managed, in accordance with EU and national regulations. The isolation of Staphylococcus aureus in milk highlights the importance of preventing contamination during milking, by adopting appropriate hygiene and safety practices at a farm level. Lysozyme activity was high compared to cow’s milk, contributing to the inhibitory activity against certain bacteria. Donkey milk was characterised by high lactose content, low caseins, low fat, higher levels of unsaturated fatty acids compared to ruminant milks. Unsaturated fatty acids and omega 3 fatty acids in particular have become known for their beneficial health effect, which is favourable for human diet. These characteristics make it suitable for infants and children affected by food intolerance/allergies to bovine milk proteins and multiple food allergies as well as for adults with dyslipidemias. It is also recommended to prevent cardiovascular diseases.

Colloid centrifugation of fresh stallion semen before cryopreservation decreased microorganism load of frozen-thawed semen without affecting seminal kinetics

Freezability of equine semen may be influenced by microorganism population of semen. The objective of this study was to verify the effect of single-layer density gradient centrifugation (SLC) of fresh semen before cryopreservation on semen's microbial load (ML) and sperm cells kinetics after freezing-thawing. For that, one ejaculate was collected from 20 healthy stallions and split into control (C) samples (cryopreserved without previous SLC) and SLC samples (subjected to SLC). Semen cryopreservation was performed according to the same protocol in both groups. Microbial load of each microorganism species and total microbial load (TML) expressed in colony-forming units (CFU/mL) as well as frozen-thawed sperm kinetics were assessed in both groups. Additional analysis of the TML was performed, subdividing the frozen-thawed samples in "suitable" (total motility ≥ 30%) and "unsuitable" (total motility < 30%) semen for freezing programs, and comparing the C and SLC groups within these subpopulations. After thawing, SLC samples had less (P < 0.05) TML (88.65 × 10(2) ± 83.8 × 10(2) CFU/mL) than C samples (155.69 × 10(2) ± 48.85 × 10(2) CFU/mL), mainly due to a reduction of Enterococcus spp. and Bacillus spp. A relationship between post-thaw motility and SLC effect on ML was noted, as only in samples with more than 30% total motility was ML reduced (P < 0.05) by SLC (from 51.33 × 10(2) ± 33.26 × 10(2) CFU/mL to 26.68 × 10(2) ± 12.39 × 10(2) CFU/mL in "suitable" frozen-thawed semen vs. 240.90 × 10(2) ± 498.20 × 10(2) to 139.30 × 10(2) ± 290.30 × 10(2) CFU/mL in "unsuitable" frozen-thawed semen). The effect of SLC on kinetics of frozen-thawed sperm cells was negligible.

Effect of breeding activity on the microflora of the external genitalia and in the semen of stallions, and the relationship between micro-organisms on the skin and on the external genitalia

A possible role of breeding activities in the composition of the microbial population in stallions' external genitalia (EG) and the relationship between micro-organisms colonizing the skin of the abdomen and the ones colonizing the EG have not been studied. In experiment 1, EG microbiological samples were collected from 41 stallions used for both natural cover and semen collection (BST) and from 18 non-breeding stallions (NBST). A higher (p < 0.05) frequency of isolation of potentially pathogenic species was found for BST. Age did not influence number of micro-organism species isolated both in BST and NBST. In experiment 2, the microbial content of the EG and semen was compared in 23 BST. Most micro-organisms isolated from the EG were present in semen, albeit with a numerically lower prevalence. In 7 stallions, six microbial species isolated from semen were absent from the EG cultures, suggesting contamination by the operator. In experiment 3, a numerically higher number of micro-organism species was isolated from the EG of 31 stallions, than from their skin of the ventral abdomen in contact with the penis or from the skin of the thorax. With the sole exception of Escherichia coli, potentially pathogenic bacteria were only isolated from the EG but not from the skin. Results suggest that breeding activity increased the number of species colonizing the EG; most species isolated from the EG were also found in semen even if with a lower frequency, and additional semen contamination seemed to occur during its manipulation. Many micro-organism species of the skin were also isolated from the penis, but independently of being or not in contact with the penis, skin did not seem to provide an adequate environment for the growth of potentially pathogenic bacteria that were isolated from EG, with the sole exception for E. coli.

Molecular epidemiology of clinical isolates of Pseudomonas aeruginosa isolated from horses in Ireland

Clinical isolates (n = 63) of Pseudomonas aeruginosa obtained from various sites in 63 horses were compared using ERIC2 RAPD PCR to determine their genetic relatedness. Resulting banding patterns (n = 24 genotypes) showed a high degree of genetic heterogeneity amongst all isolates examined, indicating a relative non-clonal relationship between isolates from these patients, employing this genotyping technique. This study characterised 63 clinical isolates into 24 distinct genotypes, with the largest cluster (genotype E) accounting for 10/63 (15.9%) of the isolates. ERIC2 RAPD PCR proved to be a highly discriminatory molecular typing tool of P. aeruginosa in isolates recovered from horses. With the adoption of several controls to aid reproducibility, this technique may be useful as an alternative to PFGE, particularly in epidemiological investigations of outbreaks where speed may be a significant parameter. This is the first report of clonal heterogeneity amongst P. aeruginosa from horses and demonstrated that ERIC RAPD PCR is a rapid method for the examination of this species in horses, which may be useful in outbreak analysis.

Infectious causes of embryonic and fetal mortality

The purpose of this review is to summarize bacterial, fungal, protozoan, and viral causes of reproductive dysgenesis in cattle, sheep, goats, pigs, horses, dogs, and cats. The clinical presentations of disease due to reproductive pathogens are emphasized, with a focus on assisting development of complete lists of causes that result in abortion and infertility in these species. Clinicians are encouraged to assess clinical presentation, create complete lists of differential diagnoses, obtain appropriate diagnostic samples, maximize diagnostic laboratory support, and avoid zoonotic infections resulting from reproductive pathogens of animals. The foundation of an accurate diagnosis of reproductive loss due to infectious pathogens facilitates the prudent use of immunization and biosecurity to minimize reproductive losses.