Methicillin-resistant Staphylococcus aureus in horses and horse personnel, 2000-2002

Companions in antimicrobial resistance: examining transmission of common antimicrobial-resistant organisms between people and their dogs, cats, and horses

SUMMARYNumerous questions persist regarding the role of companion animals as potential reservoirs of antimicrobial-resistant organisms that can infect humans. While relative antimicrobial usage in companion animals is lower than that in humans, certain antimicrobial-resistant pathogens have comparable colonization rates in companion animals and their human counterparts, which inevitably raises questions regarding potential antimicrobial resistance (AMR) transmission. Furthermore, the close contact between pets and their owners, as well as pets, veterinary professionals, and the veterinary clinic environment, provides ample opportunity for zoonotic transmission of antimicrobial-resistant pathogens. Here we summarize what is known about the transmission of AMR and select antimicrobial-resistant organisms between companion animals (primarily dogs, cats, and horses) and humans. We also describe the global distribution of selected antimicrobial-resistant organisms in companion animals. The impact of interspecies AMR transmission within households and veterinary care settings is critically reviewed and discussed in the context of methicillin-resistant staphylococci, extended-spectrum β-lactamase and carbapenemase-producing bacteria. Key research areas are emphasized within established global action plans on AMR, offering valuable insights for shaping future research and surveillance initiatives.

Antimicrobial Resistance in Equines: A Growing Threat to Horse Health and Beyond-A Comprehensive Review

The equine industry holds substantial economic importance not only in the USA but worldwide. The occurrence of various infectious bacterial diseases in horses can lead to severe health issues, economic losses, and restrictions on horse movement and trade. Effective management and control of these diseases are therefore crucial for the growth and sustainability of the equine industry. While antibiotics constitute the primary treatment strategy for any bacterial infections in horses, developing resistance to clinically important antibiotics poses significant challenges to equine health and welfare. The adverse effects of antimicrobial overuse and the escalating threat of resistance underscore the critical importance of antimicrobial stewardship within the equine industry. There is limited information on the epidemiology of antimicrobial-resistant bacterial infections in horses. In this comprehensive review, we focus on the history and types of antimicrobials used in horses and provide recommendations for combating drug-resistant bacterial infections in horses. This review also highlights the epidemiology of antimicrobial resistance (AMR) in horses, emphasizing the public health significance and transmission dynamics between horses and other animals within a One Health framework. By fostering responsible practices and innovative control measures, we can better help the equine industry combat the pressing threat of AMR and thus safeguard equine as well as public health.

Methicillin-resistant staphylococci in clinical bovine mastitis: occurrence, molecular analysis, and biofilm production

Staphylococcus aureus is an important pathogen that causes mastitis in cattle, and the emergence of methicillin-resistant S. aureus (MRSA) poses a threat to veterinary and human medicine. The aims of the study were to investigate the prevalence of MRSA and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from clinical mastitis, their ability to form biofilms, and the antimicrobial susceptibility of S. aureus strains. In addition, the Staphylococcal Cassette Chromosome mec (SCCmec) type, spa type and the presence of Panton-Valentine Leucocidin in MRSA were evaluated. A total of 326 staphylococcal strains were screened by multiplex-PCR for S. aureus and Staphylococcus intermedius group (SIG) identification. The S. aureus strains (n = 163) were subjected to phenotypic testing for antimicrobial susceptibility and biofilm formation. Molecular analysis was performed on MRSA mecA-positive strains. Of 163 S. aureus isolates, 142 strains (87.1%) were resistant to at least one antibiotic, and all 19 MRSA strains were resistant to at least four out of five antibiotics tested. All S. aureus strains harboured the icaA gene and were biofilm producers. Nineteen MR-CoNS strains were also isolated. The most prevalent spa types among MRSA were t001 (57.9%) and t037 (31.6%), while one MRSA was type t008 and one was type t041. Most MRSA were SCCmec type I (63.2%) and III (31.6%) and only one strain was type IV. None of the MRSA isolates had the PVL gene. The prevalence of multidrug-resistant S. aureus in bovine mastitis is a serious concern. The finding of MRSA with spa types predominant in humans and infrequent in Italian cows and with SCCmec infrequently found in bovine milk or cheese suggest a human origin of these strains. The ability of MRSA and MR-CoNS involved in bovine mastitis to be transferred to humans and vice versa poses a public health concern.

Comparison of In Vitro Bacterial Susceptibility to Common and Novel Equine Wound Care Dressings

Antimicrobial resistance is becoming a problem of concern in the veterinary field, necessitating the use of effective topical treatments to aid the healing of wounds. Honey has been used for thousands of years for its medicinal properties, but in recent years medical-grade Manuka honey has been used to treat infected wounds. The goal of this study was to determine the relative susceptibility of four common equine wound pathogens to ten different types of antimicrobial agents based on the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The pathogens studied include ATCC lab-acclimated Pseudomonas aeruginosa, Escherichia coli, and methicillin-resistant Staphylococcus aureus and one from an equine sample submitted to the Colorado State Veterinary Diagnostic Laboratory (Streptococcus equi ssp. zooepidemicus (Streptococcus zooepidemicus)). An additional goal of the study was to describe the comparison of bactericidal activity of medical-grade Manuka honey, local honey, and commercial, food-grade honey to other commonly used wound dressings (20% hypertonic saline, silver sulfadiazine cream, PHMB gauze, and PHMB foam). The objective is to provide veterinary practitioners with comparative data on the use of a variety of antimicrobial dressings for inhibiting the growth of common wound bacteria. MIC and MBC for Manuka, store, and local honeys were comparable to those of sterile gauze, sugar, and hypertonic saline. Across bacterial species, local honey proved to have more bactericidal activity when compared to Manuka honey and commercial, food-grade honey. The MIC and MBC for PHMB gauze and foam was consistently at a higher dilution compared to the other antimicrobials. The majority of antimicrobials exhibited stronger inhibitory and bactericidal activity against a Streptococcus zooepidemicus isolate obtained from a wound compared to other bacteria that were ATCC lab-acclimated. Additional research for in vivo applications needs to be done to see whether differences exist in effective wound management.

A look at staphylococci from the one health perspective

Staphylococcus aureus and other staphylococcal species are resident and transient multihost colonizers as well as conditional pathogens. Especially S. aureus represents an excellent model bacterium for the "One Health" concept because of its dynamics at the human-animal interface and versatility with respect to host adaptation. The development of antimicrobial resistance plays another integral part. This overview will focus on studies at the human-animal interface with respect to livestock farming and to companion animals, as well as on staphylococci in wildlife. In this context transmissions of staphylococci and of antimicrobial resistance genes between animals and humans are of particular significance.

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.

Staphylococcus aureus in Horses in Nigeria: Occurrence, Antimicrobial, Methicillin and Heavy Metal Resistance and Virulence Potentials

Staphylococcus aureus was isolated from a total of 360 nasal and groin skin swabs from 180 systematic randomly-selected horses slaughtered for meat at Obollo-Afor, Enugu State, Southeast Nigeria and antimicrobial, methicillin and heavy metal resistance profile and virulence potentials of the isolates established. Baird-Parker agar with egg yolk tellurite was used for S. aureus isolation. S. aureus isolates were confirmed biochemically and serologically using a specific S. aureus Staphytect Plus™ latex agglutination test kit. The antimicrobial resistance profile, methicillin, vancomycin and inducible clindamycin resistance, and β-lactamase production of the isolates were determined with disc diffusion. Tolerance to Copper, Cadmium, Lead and Zinc was assessed using the agar dilution method and virulence potentials were determined using phenotypic methods. Forty-three (23.9%) of the 180 horses harbored S. aureus. Some 71 S. aureus were recovered from the 360 samples. Two (2.8%) of the 71 S. aureus were methicillin-resistant S. aureus (MRSA) and 69 (97.2%) were methicillin-susceptible. MRSA was recovered from 2 (1.1%) of the 180 horses. Some 9.4% of the isolates were multiple drug-resistant (MDR). The mean multiple antibiotic resistance indices (MARI) for the isolates was 0.24. Heavy metal resistance rate of the isolates ranged between 35.4-70.4%. The isolates, including the MRSA strains, displayed virulence potentials as clumping factor and catalase, gelatinase, caseinase, heamolysin, and biofilm was at the rate of 100%, 53.5%, 43.7%, 18.3% and 23.9%, respectively. This study showed that a considerable percentage of horses slaughtered in Obollo-Afor Southeastern Nigeria are potential reservoirs of virulent multiple drug- and heavy metal-resistant S. aureus, including MRSA, that could spread to humans and the environment.

Wound swabs versus biopsies to detect methicillin resistant Staphylococcus aureus in experimental equine wounds

OBJECTIVE

To compare: (1) the load and diversity of cultivatable bacterial species isolated from tissue biopsies with cultures from surface swabs, and (2) the ability of each technique to detect methicillin-resistant Staphylococcus aureus (MRSA) in a model of MRSA-infected equine wounds.

STUDY DESIGN

Experimental in vivo study.

ANIMALS

Three light-breed adult horses.

METHODS

Four 2.5 × 2.5 cm full-thickness skin wounds were created on the dorsolateral aspect of each forelimb. Five days later, each wound was inoculated with a pure culture of MRSA (ATCC 43300). One hundred microlitres of 0, 5 × 108 , 5 × 109 or 5 × 1010 colony forming units (CFU)/ml was used to inoculate each wound. Surface swabs (Levine technique) and tissue biopsy samples (3 mm punch biopsy) were obtained at 2, 7, 14, and 21 days after inoculation. Quantitative aerobic culture was performed using routine clinical techniques.

RESULTS

A similar bacterial profile was identified from the culture of each wound-sampling technique and there was moderate correlation (R = 0.49, P < .001) between the bacterial bioburdens. Agreement was fair (κ = 0.31; 95% CI, 0.129-0.505) between the sampling techniques in identification of MRSA. Methicillin-resistant Staphylococcus aureus was isolated more frequently (P = .016) from cultures of tissue biopsies (79%; 76/96) than from surface swabs (62%; 60/96).

CONCLUSION

Bacterial load and diversity did not differ between sampling techniques but MRSA was detected more often from the cultures of tissue biopsies.

CLINICAL SIGNIFICANCE

Tissue biopsy should be preferred to culture swab in wounds where MRSA is suspected.

[Management and hygiene measures during an outbreak of herpes, influenza, strangles or infections with multidrug resistant bacteria]

The aim of this review is to describe general guidelines of hygiene measures in the horse stable as well as to provide current recommendations for an outbreak of a common infectious disease. General cleanliness, hand hygiene, avoidance of stress, regular deworming, and vaccinations belong to the basic hygiene measures in a horse herd. All new or returning equids should be submitted to a quarantine period as an important prevention measure. Repeated washing and disinfection of hands may prevent spreading of infectious agents to people and horses.The conception of a hygiene plan, including general biosecurity procedures and standard operating procedures in a case of an outbreak of an infectious disease, zoonosis, or colonization with multi-resistant bacteria is strongly recommended. As soon as the disease is suspected, extended hygiene measures including protective clothing, cleaning, disinfection, and isolation of potentially infected animals should be implemented. Prompt confirmation of the causative agent by examination of appropriate samples is crucial. It is important to adjust all safety measures based on the contagious nature of the respective pathogen and its major transmission routes. Apart from a lock-down of the stable, clinic or show grounds, the segregation of horses plays an important role. Implementation of the "traffic light system" is recommended. In this, the red group ("infected") include animals with clinical signs of the disease or that have been tested positive. All horses with possible pathogen contact should be allocated to a yellow group ("suspected") and regularly controlled for the signs of infection and fever. Clinically normal horses without contact to the infected animals belong to the green group ("healthy"). A change of protective clothing and an extensive disinfection should be performed when moving between the groups.The extended hygiene measures are to be maintained until all animals have been tested negative or fail to exhibit clinical signs of the disease for a certain time period.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): antimicrobial-resistant Staphylococcus aureus in cattle and horses

Staphylococcus aureus (S. aureus) was identified among the most relevant antimicrobial-resistant (AMR) bacteria in the EU for cattle and horses in previous scientific opinions. Thus, it has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on its eligibility to be listed, Annex IV for its categorisation according to disease prevention and control rules as in Article 9, and Article 8 for listing animal species related to the bacterium. The assessment has been performed following a methodology previously published. The outcome is the median of the probability ranges provided by the experts, which indicates whether each criterion is fulfilled (lower bound ≥ 66%) or not (upper bound ≤ 33%), or whether there is uncertainty about fulfilment. Reasoning points are reported for criteria with uncertain outcome. According to the assessment here performed, it is uncertain whether AMR S. aureus can be considered eligible to be listed for Union intervention according to Article 5 of the AHL (60-90% probability). According to the criteria in Annex IV, for the purpose of categorisation related to the level of prevention and control as in Article 9 of the AHL, the AHAW Panel concluded that the bacterium does not meet the criteria in Sections 1, 2 and 4 (Categories A, B and D; 1-5%, 5-10% and 10-33% probability of meeting the criteria, respectively) and the AHAW Panel was uncertain whether it meets the criteria in Sections 3 and 5 (Categories C and E, 33-90% and 60-90% probability of meeting the criteria, respectively). The animal species to be listed for AMR S. aureus according to Article 8 criteria include mainly mammals, birds, reptiles and fish.

Prevalence and WGS-based characteristics of Staphylococcus aureus in the nasal mucosa and pastern of horses with equine pastern dermatitis

BACKGROUND

Many contributing factors are involved in the development of equine pastern dermatitis (EPD). Among the most frequently suspected is Staphylococcus aureus, known for its pathogenic potential in skin and soft tissue infections. We therefore investigated the association between S. aureus carriage and EPD.

RESULTS

One hundred five EPD-affected horses and 95 unaffected controls were examined for the presence of methicillin-resistant and -susceptible Staphylococcus aureus (MRSA and MSSA) on the pastern skin and in the nostrils. S. aureus isolates were cultivated from swab samples on selective MSSA and MRSA chromogenic agar and identified using MALDI-TOF MS. Isolates were analysed by Illumina whole genome sequencing for genetic relatedness (cgMLST, spa typing), and for the presence of antimicrobial resistance and virulence determinants. A markedly higher proportion of samples from EPD-affected horses proved positive for S. aureus, both from the pastern (59.0 % vs. 6.3 % in unaffected horses; P<0.001), and from the nose (59.0 % vs. 8.4 %; P<0.001). Isolates belonged to 20 sequence types (ST) with lineages ST15-t084 (spa) (18 %), ST1-t127 (13 %), and ST1-t1508 (12 %) being predominant. Eight S. aureus were MRSA ST398-t011 and ST6239-t1456, and contained the staphylococcal cassette chromosome SCCmecIVa. Antimicrobial resistance genes were almost equally frequent in pastern and in nasal samples, whereas some virulence factors such as the beta-hemolysin, ESAT-6 secretion system, and some enterotoxins were more abundant in isolates from pastern samples, possibly enhancing their pathogenic potential.

CONCLUSIONS

The markedly higher prevalence of S. aureus containing specific virulence factors in affected skin suggests their contribution in the development and course of EPD.

Livestock-Associated Meticillin-Resistant Staphylococcus aureus—Current Situation and Impact From a One Health Perspective

Purpose of Review

In this article, we aim to provide an overview of the occurrence and characteristics of livestock-associated (LA-) meticillin-resistant Staphylococcus aureus (MRSA). We further question the role of LA-MRSA as a potential foodborne pathogen. We investigate recent findings and developments from a One Health perspective also highlighting current strategies and initiatives aiming to improve reporting, control, and prevention of LA-MRSA.

Recent Findings

While the overall number of invasive MRSA infections in humans is decreasing (in most European countries and the USA) or steadily increasing (in the Asia-Pacific region), the role of LA-MRSA as causative agent of invasive disease and as potential foodborne pathogen is still poorly understood. LA-MRSA prevalence in livestock remains high in many geographical regions and the acquisition of new virulence and resistance determinants constitutes a growing threat for human health.

Summary

The true incidence of LA-MRSA infections due to occupational exposure is unknown. Improved MRSA monitoring and tracking procedures are urgently needed. Strain typing is crucial to enable improved understanding of the impact of LA-MRSA on human and animal health.

Analysis of Virulence and Antimicrobial Resistance Gene Carriage in Staphylococcus aureus Infections in Equids Using Whole-Genome Sequencing

While Staphylococcus aureus is associated with significant morbidity and mortality in equids (horses, donkeys, and mules), few studies have performed whole-genome sequencing to fully categorize large collections of equine isolates. Such sequencing allows for a comprehensive analysis of the genetic lineage and relationships of isolates, as well as the virulence genes present in each, which can be important for understanding the epidemiology of strains and their range of infections. Seventy-two clinical Staphylococcus aureus isolates from equids were collected at the Texas A&M University Veterinary Medical Teaching Hospital between 2007 and 2017. Whole-genome sequencing was performed to characterize the isolates according to sequence typing, biofilm association, antimicrobial resistance, and toxin gene carriage. Of the 72 isolates, 19% were methicillin resistant, of which the majority belonged to clonal complex 8. Eighteen distinct sequence types (STs) were represented, with the most common being ST1, ST133, ST8, and ST97. Most isolates had weak or negative overall biofilm production. Toxin and antimicrobial resistance gene carriage was varied; of note, this study revealed that a large proportion of North American equine isolates carry the leucocidin PQ toxin (66% of isolates). One isolate (17-021) carried genes imparting lincosamide and high-level mupirocin resistance, a combination not previously reported in equine-derived S. aureus isolates.

IMPORTANCE This is one of the first studies to perform whole-genome sequencing (WGS) of a large collection of Staphylococcus aureus isolates, both methicillin resistant and susceptible, collected from horses. A large proportion of the isolates carry leucocidin PQ (LukPQ), making this one of the first reports of such carriage in the United States. The presence of lincosamide and high-level mupirocin resistance in a methicillin-susceptible S. aureus (MSSA) isolate highlights the importance of MSSA as a reservoir of important antimicrobial resistance genes. As microbial resistance genes on mobile genetic elements can pass between S. aureus strains and livestock-associated strains can be transferred to humans, these findings have important public health implications.

Whole genome sequencing of methicillin-resistant and methicillin-sensitive Staphylococcus aureus isolated from 4 horses in a veterinary teaching hospital and its ambulatory service

Genomic characterization was conducted on 2 methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from 2 horses hospitalized during an overlapping period of time and 2 methicillin-sensitive S. aureus (MSSA) strains isolated from 2 distinct horses. Phylogenetic proximity was traced and the genotypic and phenotypic characteristics of the antimicrobial resistance of the strains were compared. Whole genome sequencing of MRSA strains for this report was similar but differed from whole genome sequencing of MSSA strains. The MRSA strains were closely related, belonging to sequence type (ST) 612, spa type t1257, and SCCmec type IVd2B. The MSSA strains were also closely related, belonging to ST1660, spa type t3043, and having no detectable staphylococcal cassette chromosome mec elements. All MSRA and MSSA strains were Panton-Valentine leukocidin negative. There were discrepancies in the genotypic analysis and the antimicrobial susceptibility testing (phenotypic analysis) of MRSA strains for rifampin, trimethoprim-sulfamethoxazole, gentamicin, amikacin, and enrofloxacin.

Characterization of highly virulent community-associated methicillin-resistant Staphylococcus aureus ST9-SCCmec XII causing bloodstream infection in China

Previous studies have shown that livestock (LA)-MRSA ST398 evolved from a human-adapted methicillin-susceptible S. aureus (MSSA) clone. However, detailed information regarding ST9 is still unclear. Here, we characterized a community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) ST9-SCCmec XII isolate that has not been previously reported to cause serious disease in China. We obtained whole-genome sequences of one ST9-t899-XII isolate—ZY462471—from a patient with bloodstream infection without livestock contact. The antibiotic susceptibilities of ZY462471 were determined and the clinical information was extracted from medical notes and compared with twenty-seven previously sequenced genomes. Phylogenetic reconstruction was performed to investigate the probable host evolutionary origins of ZY462471, and the difference in resistome and virulence factors were investigated. Virulence assay was performed to evaluate the high virulence potential of ZY462471 and compare the virulence between the closest ST9 MSSA neighbours. Clinical data suggested that ZY462471 is a CA-MRSA. Phylogenetic analysis showed a much closer relationship of ZY462471 with human-associated MSSA ST9 isolates than other LA-MRSA ST9 isolates, suggesting that ZY462471 probably evolved from ST9 MSSA predecessors by acquiring an SCCmec cassette. Importantly, virulence assays indicated that ZY462471 was highly virulent and compared with the MSSA ST9 predecessors, ZY462471 did not show attenuated virulence. Finally, we found that ZY462471 harboured an immune evasion cluster (IEC)-carrying βC-Φ, which is typically found in human clinical S. aureus rather than LA-MRSA isolates, suggesting that ZY4762471 obtained the IEC-carrying βC-Φs from human clinical S. aureus strains. Considering its high virulence potential, this strain should be monitored to prevent more widespread dissemination.

Indications for the use of highest priority critically important antimicrobials in the veterinary sector

BACKGROUND

Among the measures taken to preserve the clinical efficacy of highest priority critically important antimicrobials (HP-CIAs), the WHO has recommended avoiding their use in food-producing animals. Little is known regarding the indications for which different antimicrobial classes are used in animals, even in countries where data on antimicrobial use are available.

OBJECTIVES

To outline, in a narrative review, the diseases for which HP-CIAs are used in veterinary medicine, highlighting incongruences with international guidelines and disease conditions where effective alternatives to HP-CIAs are missing.

METHODS

Scientific literature, national reports and expert opinion were used to describe the indications for the use of HP-CIAs in the main food-producing (pigs, cattle and poultry) and companion (horses, dogs and cats) animal species.

RESULTS

The most common indications for use of HP-CIAs are enteric and respiratory infections in pigs, cattle and poultry, urogenital infections in dogs and cats and respiratory infections in horses. In some instances, no valid and convenient alternatives to colistin and macrolides are available against certain porcine enteric and bovine respiratory pathogens. Effective, legal and convenient alternatives to HP-CIAs are also lacking for managing common infections in cats, for which oral administration is difficult, Rhodococcus equi infections in horses, some enteric and respiratory infections in poultry and MDR infections in all companion animal species.

CONCLUSIONS

Future research and stewardship programmes should focus on the disease conditions identified by this review to reduce the use of HP-CIAs in the veterinary sector.

Antimicrobial prescribing patterns in equine ambulatory practice

Antimicrobial resistance is one of the most important public health risks facing our world today. Antimicrobials are commonly prescribed in equine veterinary medicine, but limited information exists documenting their use in practice. The goal of this study was to investigate antimicrobial prescription patterns in regards to prescription frequency, duration, drug class, clinician and affected body system in an equine ambulatory setting via retrospective analysis of billing and electronic medical records. Risk factors associated with antimicrobial prescription including the nature of the visit, submission of a culture, body system affected and clinician were assessed using multivariable regression. We found that antimicrobials were prescribed in 8.5 % of visits with a median number of 3.5 (IQR 0.8-12.2) animal-defined daily doses (ADD), defined as the number of daily doses of all antimicrobials prescribed to a patient at a single visit. Aminoglycosides were the most common class of antimicrobials prescribed and trimethoprim sulfamethoxazole was the most common drug prescribed overall. Amikacin was primarily used for patients presenting with musculoskeletal signs, and the median number of ADDs for visits where amikacin was prescribed was 1 (IQR 0.9-1.9), while the median number of antimicrobial ADDs for all other visits was 4.4 (IQR 0-14.1). Statistically significant differences in antimicrobial use patterns existed across clinicians, months, years and affected body systems. Horses presenting with ocular (OR 1199; 95 % CI 204-7,037; p < 0.001) and integumentary (OR 365; 95 % CI 87.2-1532; p < 0.001) signs were most likely to be prescribed an antimicrobial. Emergency visits (OR 5.61; 95 % CI 3.19-9.89; p < 0.001) and submission of a bacterial culture (OR 3.58; 95 % CI 2.11-6.09; p < 0.001) were associated with an increased likelihood of an antimicrobial prescription. This observational study was the first to quantitatively characterize antimicrobial use patterns in equine ambulatory practice in the United States, which is an important step needed to determine appropriateness of use and develop and evaluate antimicrobial stewardship guidelines.

Equine antimicrobial therapy: Current and past issues facing practitioners

Equine antimicrobial therapy has advanced over time with the availability of increasing pharmacokinetic and pharmacodynamic studies in horses, allowing for greater evidence-based clinical decision-making. However, many challenges to optimal antimicrobial therapy remain and further research is needed to address these areas. There are a limited number of approved antimicrobials for use in horses, which creates a need for compounded preparations for clinicians. Extra-label drug use is commonplace in equine practice, which warrants continual education of veterinarians about policies and updates. Performance and competitive horses have their own unique concerns when it comes to antimicrobial use and drug testing. In keeping with the use of a broader range of antimicrobials over time, antimicrobial resistance is emerging as an important issue facing veterinary medicine, including equine practice. Another challenge is that of drug interactions and adverse drug events for which there are little scientific data available for horses, especially for critically important diseases such as Rhodococcus equi infection. Finally, much progress has been made in the availability of equine-specific antimicrobial susceptibility break points. These aid clinicians in interpreting culture and susceptibility results and antimicrobial selection. Even with these advances, continuing education and further research are needed in this area.

A retrospective study on methicillin-resistant Staphylococcus spp. isolated from horses admitted to a Canadian veterinary teaching hospital between 2008 and 2018

The goals of this retrospective study were to: determine the frequency of methicillin-resistant Staphylococcus spp. (MRS) isolated from horses admitted to an equine veterinary teaching hospital in Quebec from 2008 to 2018, investigate the patterns of antimicrobial resistance (AMR), and evaluate the distribution of MRS and methicillin-sensitive Staphyloccocus spp. (MSS) by body site. During this period, 311 Staphylococcus spp. were isolated from 273 horses and 127 of these isolates were submitted to antimicrobial susceptibility testing. Of these 127 isolates, 24 (18.9%) were MRS, and among the S. aureus (n = 76), 19 (25%) were MRS. The odds of detecting an MRS increased (25%) each year [95% confidence interval (CI) (1% to 55%), P = 0.039]. The highest frequencies of resistance were to tetracycline and gentamicin. Among the MRS isolates, 12% were susceptible to both tetracycline and gentamicin. The most frequently sampled body sites were "soft-tissues." There was no significant difference (P = 0.93) in the body site distribution of MRS and MSS isolates.

Vancomycin intermediate resistant Staphylococcus aureus in the nasal cavity of asymptomatic individuals: a potential public health challenge

Background

The potential of transmitting multidrug resistant Staphylococcus aureus from asymptomatic individuals to healthy individuals could constitute a great challenge to antimicrobial therapy.

Methods

The antibiograms of the S. aureus from asymptomatic individuals were determined by disk diffusion and agar dilution assay techniques with different antibiotics and vancomycin.

Results

Of the 152 S. aureus isolated, (59)38.8% isolates were multi-drug resistant strains. Streptomycin was the most effective and inhibited (135)88.82% of the isolates while ceftazidime inhibited (24)15.8% of the isolates. While (82)54.0% of the isolates inhibited by cefuroxime had resistant colonies within their inhibition zones (Rc) and ofloxacin inhibited (100)65.8% of the isolates without having resistant colonies within the inhibition zones, ceftazidime inhibited (7)4.6% of the isolates with resistant colonies within the inhibition zones. Subjecting the isolates to vancomycin showed that (27)17.8% were resistant to 2 µg/ml, (43)28.3% were resistant to 4 µg/ml and (27)17.8% of the isolates were simultaneously resistant to both concentrations of vancomycin. Although (100)65.8% of the isolates had MAR_index ≥0.2, (52)34.2% of the isolates had MAR_index ≤ 0.2 and (65)428% of the isolates were considered multidrug resistant strains.

Conclusion

The isolation of multi-drug and vancomycin intermediate resistant strains of S. aureus in high percentage, in this study, presents a great threat to clinicians and general populace. The vancomycin intermediate resistant S. aureus (VISA) in asymptomatic individuals could be a critical concern to the therapeutic dilemma to be added to the presence of multi-drug resistance. A more sustainable therapy must be in place to prevent its dissemination or the outbreak of its infection.

Investigation of the Shedding of Selected Respiratory Pathogens in Healthy Horses Presented for Routine Dental Care

The main objective of the study was to determine the frequency of detection of selected infectious respiratory viruses and bacteria in healthy horses presented over a 12-month period for routine dental care at 2 veterinary hospitals. Nasal secretions were collected from 579 horses and tested for equine herpesviruses (EHV-1, EHV-2, EHV-4, EHV-5), equine influenza virus (EIV), equine rhinitis A and B viruses (ERAV, ERBV), Streptococcus equi subspecies equi (S equi), S equi subspecies zooepidemicus (S zooepidemicus), and methicillin-resistant Staphylococcus aureus (MRSA) using routine diagnostic quantitative polymerase chain reaction assays. True respiratory pathogens (EHV-1, EHV-4, EIV, ERBV, and MRSA) were detected in 129 (22%) of the horses. Commensal respiratory pathogens (EHV-2, EHV-5, and S zooepidemicus) were detected in 515 (89%) of the study horses. ERAV and S equi were not detected in any of the study horses. The horses showed statistical differences between the 2 veterinary hospitals in regard to breed, age, presence of nasal discharge, rectal temperature, and detection of true and commensal respiratory pathogens. The data generated from the present study supports the risk for the transmission of true and commensal respiratory pathogens from subclinical shedders to susceptible horses. Equine veterinarians performing routine dental care should engage in routine biosecurity practices, with the goal to reduce disease spread.

Antimicrobial susceptibility patterns of bacterial isolates cultured from synovial fluid samples from horses with suspected septic synovitis: 108 cases (2008-2017)

OBJECTIVE

To describe the antimicrobial susceptibility patterns of the most commonly isolated bacteria cultured from synovial fluid samples from horses with suspected septic synovitis treated at an equine referral hospital between May 1, 2008, and September 24, 2017.

SAMPLE

131 synovial fluid samples from 108 client-owned horses.

PROCEDURES

A retrospective medical record search was conducted to identify horses with suspected septic synovitis and results of synovial fluid bacterial culture and antimicrobial susceptibility testing. Data collected included signalment, known or suspected origin of synovial contamination, synovial structures affected, antimicrobial treatment, and results of synovial fluid cytologic evaluation and bacterial culture and susceptibility testing. Horses were grouped as adults (≥ 6 months old) or foals (< 6 months old).

RESULTS

Results of bacterial culture were positive for 34 of 70 (49%) and 18 of 61 (30%) samples from 68 adult horses and 40 foals, respectively. Gram-positive bacteria were more common in adult horses, whereas gram-negative bacteria were more common in foals. No multidrug-resistant microorganisms were identified. For adult horses, 92% (23/25) of gram-positive isolates tested with penicillin and gentamicin were susceptible to the combination. For foals, 94% (15/16) of isolates tested with penicillin, gentamicin, or both had susceptibility to 1 or both antimicrobials.

CONCLUSIONS AND CLINICAL RELEVANCE

Periodic review of bacterial profiles and antimicrobial susceptibility in horses with septic synovitis can help to detect early changes in bacterial pressure and antimicrobial resistance. Findings suggested that in the geographic area we serve, a combination of penicillin and gentamicin would be an effective empirical antimicrobial treatment for most horses with septic synovitis while results of bacterial culture and susceptibility are pending.

Nasogastric Intubation as Health and Safety Risk in Equine Practice-A Questionnaire

Placing a nasogastric tube can be a life-saving act for a horse but is considered an occupational hazard for veterinarians. An online questionnaire was performed to assess and specify potential risks. 123 equine veterinarians completed the survey, and the majority admitted using the mouth to handle the end of the nasogastric tube (sucking or blowing air) and having accidentally swallowed or aspirated stomach content or medications. This can potentially lead to aspiration pneumonia or pneumonitis. Mineral oil seems to be especially dangerous as aspiration may be asymptomatic at the beginning and lipoid pneumonitis may develop. Furthermore, 60% of responders would also handle the tube with their mouth if the horse was presented with fever and diarrhea or reflux formation, which might be affected by Salmonella sp. or Clostridium difficile producing toxins. The fact that nasogastric tubes are rarely being disinfected increases the risk of infection. 50% of veterinarians would use their mouth to suck or blow air into the tube during nasogastric intubation, even if the patient was presented with suspected poisoning. Rodenticide zinc phosphide is particularly dangerous as its breakdown product is a highly toxic gas. Inhalation leads to serious symptoms in humans, including pulmonary edema and neurological signs. Alternatives to mouth use (lavage, big syringe, or suction pump) when passing a tube should be considered, especially if a patient is presented with duodenitis-proximal jejunitis, diarrhea, or suspected poisoning. Awareness needs to be raised among veterinarians that nasogastric intubation is an extremely hazardous occupational practice.

Antimicrobial resistance in bacteria isolated from diseased horses in France

BACKGROUND

Horses are one of the potential reservoirs of antimicrobial resistance (AMR) determinants that could be transferred to human subjects.

OBJECTIVE

To describe the AMR patterns of major bacteria isolated from diseased horses in France.

STUDY DESIGN

Retrospective observational study.

METHODS

Data collected between 2012 and 2016 by RESAPATH, the French national surveillance network for AMR, were analysed. Only antimicrobials relevant in veterinary and human medicine for the isolated bacteria were considered. Mono- and multidrug resistance were calculated. The resistance proportions of major equine diseases were assessed and compared. Where data permitted, resistance trends were investigated using nonlinear analysis (generalised additive models).

RESULTS

A total of 12,695 antibiograms were analysed. The five most frequently isolated bacteria were Streptococcus spp., Escherichia coli, Pseudomonas spp., Staphylococcus aureus, Pantoea spp. and Klebsiella spp. The highest proportions of resistance to gentamicin were found for S. aureus (22.1%) and Pseudomonas spp. (26.9%). Klebsiella spp. and E. coli had the highest proportions of resistance to trimethoprim-sulfamethoxazole (15.5 and 26.2%, respectively). Proportions of resistance to tetracycline were among the highest for all the bacteria considered. Resistance to third-generation cephalosporins was below 10% for all Enterobacteriaceae. The highest proportions of multidrug resistance (22.5%) were found among S. aureus isolates, which is worrying given their zoonotic potential. From 2012 to 2016, resistance proportions decreased in Pseudomonas spp. isolates, but remained the same for S. aureus. For Streptococcus spp. and E. coli, resistance proportions to trimethoprim-sulfamethoxazole increased.

MAIN LIMITATIONS

Since antibiograms are not systematic analyses, any selection bias could impact the results.

CONCLUSIONS

Such studies are essential to estimate the magnitude of the potential threat of AMR to public health, to design efficient control strategies and to measure their effectiveness. These findings may also guide the initial empirical treatment of horse diseases.

Investigation of methicillin-resistant Staphylococcus aureus among clinical isolates from humans and animals by culture methods and multiplex PCR

Background

Staphylococcus aureus is responsible for large numbers of hospital-related and community-acquired infections. In this study, we investigated the presence of S. aureus and methicillin-resistant S. aureus (MRSA) in 100 samples from animals (55 cattle, 36 dogs, and 9 cats) and 150 samples from hospitalized human patients. The samples were collected from healthy and diseased animals and from diseased humans and included milk, wound swab, pus, exudates, nasal swab and diabetic ulcer. Initially, S. aureus was isolated and identified by colony morphology, Gram staining, and biochemical tests (catalase and coagulase tests). The S. aureus-positive samples were examined by polymerase chain reaction (PCR) to determine their MRSA status.

Results

Of the 100 animal samples, 29 were positive for S. aureus. Four samples (13.8%) from dogs were MRSA-positive, but samples from cattle and cats were MRSA-negative. Of the 150 human samples we collected, 64 were S. aureus-positive and, of these, 34 (53.1%) were MRSA-positive. Most (28%) of the MRSA samples were isolated from surgical wound swabs, followed by the pus from skin infections (11%), exudates from diabetic ulcers (6%), exudates from burns (4%), and aural swabs (3%). By contrast, a low MRSA detection rate (n = 4) was seen in the non-human isolates, where all MRSA bacteria were isolated from nasal swabs from dogs. The antimicrobials susceptibility testing results showed that S. aureus isolates with mecA genes showed resistance to penicillin (100%), oxacillin (100%), erythromycin (73.5%), ciprofloxacin (70.6%), and gentamicin (67.7%). The lowest resistance was found against ceftazidime, and no vancomycin-resistant isolates were obtained.

Conclusions

We detected S. aureus and MRSA in both human and canine specimens. Isolates were found to be resistant to some of the antimicrobials available locally. MRSA carriage in humans and animals appears to be a great threat to effective antimicrobials treatment. The prudent use of antimicrobials will reduce the antimicrobial resistance. Our findings will help to find the most appropriate treatment and to reduce antimicrobial resistance in the future by implementing prudent use of antimicrobials. Further studies are required to better understand the epidemiology of MRSA human–animal inter-species transmission in Bangladesh.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1611-0) contains supplementary material, which is available to authorized users.

Frequencies and Antimicrobial Susceptibility of Methicillin-Resistant Staphylococcus aureus (MRSA) Isolated from Horses in South Korea

Background:

Methicillin-ResistantStaphylococcus Aureus(MRSA) has become one of the most prevalent pathogens in animals and humans giving rise to various diseases. MRSA infection in horses and transmission between horses and humans have dramatically increased recently.

Objective:

This study investigated the isolation frequency and antimicrobial susceptibility of MRSA isolated from horses in South Korea.

Method:

Screening of the MRSA isolates was conducted by conventional methods and multiplex Polymerase Chain Reaction (PCR). Minimum Inhibitory Concentration (MIC) of oxacillin was determined by the broth microdilution test method. Overall antibiogram was obtained by disk diffusion susceptibility test. All antimicrobial tests were conducted in accordance with the Clinical and Laboratory Standards Institute (CLSI) guidelines.

Results:

S. aureuswas isolated from 116 (19.46%) of 596 horses tested. Of the 116S. aureusisolates, 52 (8.72%) strains were identified as MRSA by multiplex PCR. Among the 52 MRSA strains, 24 (46.15%) and 28 (53.85%) were oxacillin-resistant MRSA (OR-MRSA) and oxacillin-susceptible MRSA (OS-MRSA), respectively. OR-MRSA showed the highest susceptibility to florfenicol (100.00%), followed by doxycycline (95.83%), cefepime (91.67%), tetracycline (75.00%), and trimethoprim/sulphamethoxazole (70.83%). OS-MRSA showed the highest susceptibility to florfenicol (100.00%) and trimethoprim/sulphamethoxazole (100.00%), followed by cefoxitin (96.43%), ciprofloxacin (92.86%), enrofloxacin (92.86%), lincomycin + spectinomycin (89.29%), cefuroxime (89.29%), and cefonicid (89.29%).

Conclusion:

This study may facilitate treatment and prevention of MRSA infections and further benefit not only horses, but also people related with horse farms, horse riding clubs and animal hospitals.

An epidemiologic study of antimicrobial resistance of Staphylococcus species isolated from equine samples submitted to a diagnostic laboratory

Background

Antimicrobial resistance limits traditional treatment options and increases costs. It is therefore important to estimate the magnitude of the problem so as to provide empirical data to guide control efforts. The aim of this study was to investigate the burden and patterns of antimicrobial resistance (AMR) among equine Staphylococcus samples submitted to the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) from 1993 to 2009. Retrospective data of 1711 equine Staphylococcus samples submitted to the UKVDL during the time period 1993 to 2009 were included in the study. Antimicrobial susceptibility testing, that included 16 drugs, were performed using cultures followed by the Kirby-Bauer disk diffusion susceptibility test. The proportion of resistant isolates by animal breed, species of organism, sample source, and time period were computed. Chi-square and Cochran-Armitage trend tests were used to identify significant associations and temporal trends, respectively. Logistic regression models were used to investigate predictors of AMR and multidrug resistance (MDR).

Results

A total of 66.3% of the isolates were resistant to at least one antimicrobial, most of which were Staphylococcus aureus (77.1%), while 25.0% were MDR. The highest level of resistance was to penicillins (52.9%). Among drug classes, isolates had the highest rate of AMR to at least one type of β-lactams (49.2%), followed by aminoglycosides (30.2%). Significant (p < 0.05) associations were observed between odds of AMR and horse breed, species of organism and year. Similarly, significant (p < 0.05) associations were identified between odds of MDR and breed and age. While some isolates had resistance to up to 12 antimicrobials, AMR profiles featuring single antimicrobials such as penicillin were more common than those with multiple antimicrobials.

Conclusion

Demographic factors were significant predictors of AMR and MDR. The fact that some isolates had resistance to up to 12 of the 16 antimicrobials assessed is quite concerning. To address the high levels of AMR and MDR observed in this study, future studies will need to focus on antimicrobial prescription practices and education of both practitioners and animal owners on judicious use of antimicrobials to slow down the development of resistance.

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in Horses, Cats, and Dogs Over a 5-Year Period in France

Methicillin-resistant Staphylococcus aureus (MRSA) has been reported as a worldwide pathogen in humans and animals including companion animals, i.e., cats, dogs, and horses. France lacked a comprehensive nationwide study describing the molecular features of MRSA circulating among companion animals over a large period of time. Here is reported the characterization of 130 non-duplicate clinical MRSA isolates collected from those three animal species from 2010 to 2015 through the French national Resapath network. Characterization of isolates was performed using phenotypic (antimicrobial susceptibility tests) and molecular (DNA arrays, spa-typing) methods. A horse-specific epidemiology was observed in France with the large dissemination of a unique clone, the CC398 clone harboring a Staphylococcal chromosomal cassette mec (SCCmec) type IV and spa-type t011. It was even the unique clone collected in 2015 whereas the clone CC8 USA500 (SCCmec type IV), classically described in horses, was present until 2014. Contrarily, cats and dogs were mainly infected by human-related MRSA isolates, i.e., clones usually reported in human infections, thus mirroring the human epidemiology in hospitals in France. Isolates belonging to the CC398 clone (SCCmec type IV or V) were also identified in 21.4% of dogs' and 26.5% of cats' MRSA isolates. In order to differentiate human-related from CC398 MRSA, tetracycline-resistance [or tet(M) detection] could be useful since this resistance is scarce in human-related strains but constant in CC398 MRSA isolates. In all, our data give a nationwide epidemiological picture of MRSA in companion animals over a 5-year period in France, adding further epidemiological information on the contribution of those animal species to a major public health issue. Considering the wide dissemination of CC398 MRSA isolates and the fact that 11/64 (17.2%) of them presented the Immune Evasion Cluster which enhances CC398 capacities to colonize humans, a specific attention should be paid in the coming years to determine the risk associated to the transmission in people in frequent contacts with companion animals. Our data also show that the prevalence of MRSA has likely decreased in cats, dogs, and horses between 2012 and 2015 in France. This trend should be monitored in the years to come.

Recommendations for approaches to meticillin-resistant staphylococcal infections of small animals: diagnosis, therapeutic considerations and preventative measures.: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology

BACKGROUND

Multiple drug resistance (MDR) in staphylococci, including resistance to the semi-synthetic penicillinase-resistant penicillins such as meticillin, is a problem of global proportions that presents serious challenges to the successful treatment of staphylococcal infections of companion animals.

OBJECTIVES

The objective of this document is to provide harmonized recommendations for the diagnosis, prevention and treatment of meticillin-resistant staphylococcal infections in dogs and cats.

METHODS

The authors served as a Guideline Panel (GP) and reviewed the literature available prior to September 2016. The GP prepared a detailed literature review and made recommendations on selected topics. The World Association of Veterinary Dermatology (WAVD) provided guidance and oversight for this process. A draft of the document was presented at the 8th World Congress of Veterinary Dermatology (May 2016) and was then made available via the World Wide Web to the member organizations of the WAVD for a period of three months. Comments were solicited and posted to the GP electronically. Responses were incorporated by the GP into the final document.

CONCLUSIONS

Adherence to guidelines for the diagnosis, laboratory reporting, judicious therapy (including restriction of use policies for certain antimicrobial drugs), personal hygiene, and environmental cleaning and disinfection may help to mitigate the progressive development and dissemination of MDR staphylococci.

An Exploratory Descriptive Study of Antimicrobial Resistance Patterns of Staphylococcus Spp. Isolated from Horses Presented at a Veterinary Teaching Hospital

BACKGROUND

Antimicrobial resistant Staphylococcus are becoming increasingly important in horses because of the zoonotic nature of the pathogens and the associated risks to caregivers and owners. Knowledge of the burden and their antimicrobial resistance patterns are important to inform control strategies. This study is an exploratory descriptive investigation of the burden and antimicrobial drug resistance patterns of Staphylococcus isolates from horses presented at a veterinary teaching hospital in South Africa.

METHODS

Retrospective laboratory clinical records of 1027 horses presented at the University of Pretoria veterinary teaching hospital between 2007 and 2012 were included in the study. Crude and factor-specific percentages of Staphylococcus positive samples, antimicrobial resistant (AMR) and multidrug resistant (MDR) isolates were computed and compared across Staphylococcus spp., geographic locations, seasons, years, breed and sex using Chi-square and Fisher's exact tests.

RESULTS

Of the 1027 processed clinical samples, 12.0% were Staphylococcus positive. The majority of the isolates were S. aureus (41.5%) followed by S. pseudintermedius (14.6%). Fifty-two percent of the Staphylococcus positive isolates were AMR while 28.5% were MDR. Significant (p < 0.05) differences in the percentage of samples with isolates that were AMR or MDR was observed across seasons, horse breeds and Staphylococcus spp. Summer season had the highest (64.3%) and autumn the lowest (29.6%) percentages of AMR isolates. Highest percentage of AMR samples were observed among the Boerperds (85.7%) followed by the American saddler (75%) and the European warm blood (73.9%). Significantly (p < 0.001) more S. aureus isolates (72.5%) were AMR than S. pseudintermedius isolates (38.9%). Similarly, significantly (p < 0.001) more S. aureus (52.9%) exhibited MDR than S. pseudintermedius (16.7%). The highest levels of AMR were towards β-lactams (84.5%) followed by trimethoprim/sulfamethoxazole (folate pathway inhibitors) (60.9%) while the lowest levels of resistance were towards amikacin (14.%).

CONCLUSIONS

This exploratory study provides useful information to guide future studies that will be critical for guiding treatment decisions and control efforts. There is a need to implement appropriate infection control, and judicious use of antimicrobials to arrest development of antimicrobial resistance. A better understanding of the status of the problem is a first step towards that goal.

Environmental surveillance identifies multiple introductions of MRSA CC398 in an Equine Veterinary Hospital in the UK, 2011-2016

Bacterial environmental and surgical site infection (SSI) surveillance was implemented from 2011–2016 in a UK Equine Referral Veterinary Hospital and identified 81 methicillin-resistant Staphylococcus aureus (MRSA) isolates. A cluster of MRSA SSIs occurred in early 2016 with the isolates confirmed as ST398 by multilocus sequence typing (MLST), which prompted retrospective analysis of all MRSA isolates obtained from the environment (n = 62), SSIs (n = 13) and hand plates (n = 6) in the past five years. Sixty five of these isolates were typed to CC398 and a selection of these (n = 38) were further characterised for resistance and virulence genes, SCCmec and spa typing. Overall, MRSA was identified in 62/540 (11.5%) of environmental samples, 6/81 of the hand-plates (7.4%) and 13/208 of the SSIs (6.3%). spa t011 was the most frequent (24/38) and Based Upon Repeat Pattern (BURP) analysis identified spa t011 as one of the two group founders of the main spa CC identified across the five years (spa CC011/3423). However, 3 singletons (t073, t786, t064) were also identified suggesting separate introductions into the hospital environment. This long-term MRSA surveillance study revealed multiple introductions of MRSA CC398 in a UK Equine Hospital, identifying an emerging zoonotic pathogen so far only sporadically recorded in the UK.

Prevalence of Methicillin-Resistant Staphylococcus aureus from Equine Nasopharyngeal and Guttural Pouch Wash Samples

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is recognized as a cause of nosocomial infections in both human and veterinary medicine. Studies that examine the nasopharynx and guttural pouches of the horse as carriage sites for MRSA have not been reported.

HYPOTHESIS/OBJECTIVE

MRSA colonizes the nasopharynx and guttural pouch of horses. To determine the prevalence of MRSA in equine nasopharyngeal wash (NPW) and guttural pouch lavage (GPL) samples in a field population of horses.

SAMPLES

One hundred seventy-eight samples (123 NPW and 55 GPL) from 108 horses.

METHODS

Prospective study. Samples were collected from a convenience population of clinically ill horses with suspected Streptococcus equi subsp. equi (S. equi) infection, horses convalescing from a known S. equi infection, and asymptomatic horses undergoing S. equi screening. Samples were submitted for S. aureus aerobic bacterial culture with mannitol salt broth and two selective agars (cefoxitin CHROMagar as the PBP2a inducer and mannitol salt agar with oxacillin). Biochemical identification of Staphylococcus species and pulsed-field gel electrophoresis (PFGE), to determine clonal relationships between isolates, were performed.

RESULTS

Methicillin-resistant Staphylococcus (MRS) was isolated from the nasopharynx of 7/108 (4%) horses. Three horses had MRSA (2.7%), and 4 had MR-Staphylococcus pseudintermedius (MRSP). MRSA was isolated from horses on the same farm. PFGE revealed the 3 MRSA as USA 500 strains.

CONCLUSIONS AND CLINICAL IMPORTANCE

Sampling the nasopharynx and guttural pouch of community-based horses revealed a similarly low prevalence rate of MRSA as other studies sampling the nares of community-based horses. More study is required to determine the need for sampling multiple anatomic sites when screening horses for MRSA.

Diversity of Staphylococcus aureus Isolates in European Wildlife

Staphylococcus aureus is a well-known colonizer and cause of infection among animals and it has been described from numerous domestic and wild animal species. The aim of the present study was to investigate the molecular epidemiology of S. aureus in a convenience sample of European wildlife and to review what previously has been observed in the subject field. 124 S. aureus isolates were collected from wildlife in Germany, Austria and Sweden; they were characterized by DNA microarray hybridization and, for isolates with novel hybridization patterns, by multilocus sequence typing (MLST). The isolates were assigned to 29 clonal complexes and singleton sequence types (CC1, CC5, CC6, CC7, CC8, CC9, CC12, CC15, CC22, CC25, CC30, CC49, CC59, CC88, CC97, CC130, CC133, CC398, ST425, CC599, CC692, CC707, ST890, CC1956, ST2425, CC2671, ST2691, CC2767 and ST2963), some of which (ST2425, ST2691, ST2963) were not described previously. Resistance rates in wildlife strains were rather low and mecA-MRSA isolates were rare (n = 6). mecC-MRSA (n = 8) were identified from a fox, a fallow deer, hares and hedgehogs. The common cattle-associated lineages CC479 and CC705 were not detected in wildlife in the present study while, in contrast, a third common cattle lineage, CC97, was found to be common among cervids. No Staphylococcus argenteus or Staphylococcus schweitzeri-like isolates were found. Systematic studies are required to monitor the possible transmission of human- and livestock-associated S. aureus/MRSA to wildlife and vice versa as well as the possible transmission, by unprotected contact to animals. The prevalence of S. aureus/MRSA in wildlife as well as its population structures in different wildlife host species warrants further investigation.

Characterisation of methicillin-resistant Staphylococcus aureus clinical isolates from animals in New Zealand, 2012-2013, and subclinical colonisation in dogs and cats in Auckland

AIMS

To characterise methicillin-resistant Staphylococcus aureus (MRSA) isolates from infection sites in animals in New Zealand and assess the prevalence of subclinical MRSA colonisation in dogs and cats attending veterinary clinics in Auckland.

METHODS

MRSA isolates from clinical specimens obtained by the main New Zealand veterinary diagnostic laboratories between June 2012 and June 2013, were genotypically characterised by DNA microarray hybridisation analysis and spa typing. In addition, nasal or perineal skin swabs collected from a cross-sectional sample of dogs (n=361) and cats (n=225) attending 29 veterinary clinics in Auckland during the same period were analysed for MRSA by culture.

RESULTS

Eight MRSA clinical isolates were submitted for characterisation by the participating laboratories. The isolates originated from five dogs, including two isolates from the same dog, one foal, and one isolate had no identification of the source. The strain-types identified were AK3 (ST-5 SCCmecIV t045; n=1), USA500 (ST8 SCCmecIV t064; n=1), WSPP (ST30 SCCmecIV t019; n=1), Rhine Hesse (ST5 SCCmecII t002; n=2), and EMRSA-15 (ST22 SCCmecIV t032; n=3). No MRSA were isolated from 586 cultured swabs. Methicillin-susceptible S. aureus were detected in 9/257 (3.5%) swabs and non-aureus staphylococci in 22/257 (8.5%) swabs. The estimated true MRSA subclinical colonisation prevalence was 0%, with an upper 95% CI boundary of 1.9% for cats and 1.4% for dogs.

CONCLUSIONS

The modest number of MRSA isolates submitted for this study by the participating laboratories suggests clinical MRSA infection in animals in New Zealand continues to be sporadic. The wide variety of strain-types found mirrored the evolving strain-type diversity observed in humans. We cannot rule out bias due to the non-random sampling of dogs and cats, but the apparent colonisation prevalence of 0% was consistent with the low prevalence of subclinical colonisation in humans in New Zealand. These similarities indicate the epidemiology of animal and human MRSA infections are linked.

CLINICAL RELEVANCE

In the last decade, the prevalence of human MRSA infections in New Zealand has steadily increased. This is the second published study of MRSA in animals in New Zealand. The results indicate clinical MRSA infection in animals remains sporadic, but the diversification of the strain-types may pose new therapeutic challenges to veterinarians, due to their diverse resistome.

Meticillin-resistant Staphylococcus aureus colonisation and infection in Thoroughbred racehorses and veterinarians in Japan

Meticillin-resistant Staphylococcus aureus (MRSA) infections have been confirmed in hospitalised Thoroughbred racehorses at the hospitals of two training centres in Japan since 2009. To investigate the source of infection, the authors examined the rate of nasal MRSA colonisation in 600 healthy Thoroughbred racehorses, 53 veterinarians and 16 office staff at the racehorse hospitals of the two training centres. MRSA was not isolated from healthy Thoroughbred racehorses or hospital office staff. However, MRSA was isolated from 16 veterinarians (30.1 per cent), and the colonisation rate was significantly higher in veterinarians than in the office staff of the same hospitals. Also, 10 of the 16 MRSA strains (62.5 per cent) isolated from veterinarians were classified as type II by staphylococcal cassette chromosome mec (SCCmec) typing and ST5 by multilocus sequence typing. Pulsed-field gel electrophoresis analysis demonstrated that these 10 MRSA strains of SCCmec type II and ST5 were genetically identical or very similar to 9 MRSA strains isolated from infected horses hospitalised at these hospitals between 2009 and 2013. These results indicate that SCCmec type II and ST5 MRSA strains were probably transmitted between veterinarians and infected horses.

A methicillin-resistant Staphylococcus aureus (MRSA) Sequence Type 8, spa type t11469 causing infection and colonizing horses in Italy

A Methicillin-resistantStaphylococcus aureus(MRSA) was isolated in Italy from a pathological sample of a mare presenting chronic purulent sinusitis and that had undergone frontal-sinus surgery three months before. Humans, horses, dogs and environmental samples were subsequently collected at the mare's stable and at the Veterinary Hospital, where the mare was operated/hospitalized, and screened for the presence of MRSA that was detected from other horses and from the environment at both sites. All the MRSA isolates belonged to clonal complex (CC)8, ST8-t11469-SCCmec-IVa, and showed similar phenotypic and genetic multidrug resistance patterns and macrorestriction-pulsed-field gel electrophoresis profiles. The only MRSA detected from humans was a CC1, ST1-t127-SCCmec-IVa. This paper represents the first report of a clinical MRSA infection in a horse in Italy. This study also supports the opinion that improper use of antibiotics and hospitalization/surgery can represent risk factors for MRSA colonization/infection in horses, and that the environment is among important sources for exposure.

MRSA in equine hospitals and its significance for infections in humans

MRSA infections in equine clinics were reported from Northern America, Europe, Australia, and Japan. The majority of nosocomial infections in horses is obviously associated with particular MRSA clonal lineages. As already observed for epidemic MRSA in human hospitals more than 10 years ago, a dynamics of MRSA clonal lineages is also observed in European equine clinics: clonal lineages belonging to clonal complex (CC) 8 are on the retreat whereas MRSA attributed to CC398 become increasingly prevalent. The majority of CC398 isolates belong to a subpopulation which is particularly associated with equine hospitals as indicated by molecular typing. When emerging in equine clinics, MRSA from horses were also found as nasal colonizers of veterinary personnel. MRSA exhibiting the typing characteristics of MRSA known from equine clinics are obviously rare among MRSA from infections in humans. Although rare so far epidemic MRSA from human hospitals (HA-MRSA, e.g., ST22, ST225) have been isolated from nosocomial infections in horses and need particular attention in further surveillance.

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Isolated from Australian Veterinarians

This work investigated the molecular epidemiology and antimicrobial resistance of methicillin-resistant Staphylococcus aureus (MRSA) isolated from veterinarians in Australia in 2009. The collection (n = 44) was subjected to extensive molecular typing (MLST, spa, SCCmec, dru, PFGE, virulence and antimicrobial resistance genotyping) and antimicrobial resistance phenotyping by disk diffusion. MRSA was isolated from Australian veterinarians representing various occupational emphases. The isolate collection was dominated by MRSA strains belonging to clonal complex (CC) 8 and multilocus sequence type (ST) 22. CC8 MRSA (ST8-IV [2B], spa t064; and ST612-IV [2B], spa variable,) were strongly associated with equine practice veterinarians (OR = 17.5, 95% CI = 3.3–92.5, P < 0.001) and were often resistant to gentamicin and rifampicin. ST22-IV [2B], spa variable, were strongly associated with companion animal practice veterinarians (OR = 52.5, 95% CI = 5.2–532.7, P < 0.001) and were resistant to ciprofloxacin. A single pig practice veterinarian carried ST398-V [5C2], spa t1451. Equine practice and companion animal practice veterinarians frequently carried multiresistant-CC8 and ST22 MRSA, respectively, whereas only a single swine specialist carried MRSA ST398. The presence of these strains in veterinarians may be associated with specific antimicrobial administration practices in each animal species.

Methicillin-resistant Staphylococcus aureus ulcerative keratitis in a Thoroughbred racehorse

We report the first case of methicillin-resistant Staphylococcus aureus (MRSA) keratitis in a racehorse. A 5-year-old mare developed punctate keratitis after racing. The corneal ulcer continued to expand despite ophthalmic antimicrobial therapy. On day 6, a conjunctival graft surgery was performed. The mare was euthanized, following colitis and laminitis development on day 10. MRSA was isolated from the corneal swab taken at the time of euthanasia. Immunohistochemical analysis demonstrated gram-positive and anti-S. aureus monoclonal antibody-positive cocci infiltration of the corneal stroma; and a diagnosis of MRSA ulcerative keratitis was made. An ophthalmic antimicrobial against the isolated MRSA did not improve the ocular lesion. The MRSA strain was found to be staphylococcal cassette chromosome mec type II, a strain frequently isolated from humans in Japan.

Eradication of methicillin-resistant Staphylococcus aureus and of Enterobacteriaceae expressing extended-spectrum beta-lactamases on a model pig farm

Colonization of livestock with bacteria resistant to antibiotics is considered a risk for the entry of drug-resistant pathogens into the food chain. For this reason, there is a need for novel concepts to address the eradication of drug-resistant commensals on farms. In the present report, we evaluated the decontamination measures taken on a farm contaminated with methicillin-resistant Staphylococcus aureus (MRSA) and Enterobacteriaceae expressing extended-spectrum β-lactamases (ESBL-E). The decontamination process preceded the conversion from piglet breeding to gilt production. Microbiological surveillance showed that the decontamination measures eliminated the MRSA and ESBL-E strains that were detected on the farm before the complete removal of pigs, cleaning and disinfection of the stable, and construction of an additional stable meeting high-quality standards. After pig production was restarted, ESBL-E remained undetectable over 12 months, but MRSA was recovered from pigs and the environment within the first 2 days. However, spa (Staphylococcus aureus protein A gene) typing revealed acquisition of an MRSA strain (type t034) that had not been detected before decontamination. Interestingly, we observed that a farmworker who had been colonized with the prior MRSA strain (t2011) acquired the new strain (t034) after 2 months. In summary, this report demonstrates that decontamination protocols similar to those used here can lead to successful elimination of contaminating MRSA and ESBL-E in pigs and the stable environment. Nevertheless, decontamination protocols do not prevent the acquisition of new MRSA strains.

Methicillin-Resistant Staphylococcus aureus spa Type t002 Outbreak in Horses and Staff at a Veterinary Teaching Hospital after Its Presumed Introduction by a Veterinarian

Methicillin-resistant Staphylococcus aureus (MRSA) infection and colonization, involving MRSA strains which differ from common human health care-associated clones, have become serious emerging conditions in equine veterinary hospitals. In 2010, MRSA spa type t535 caused an outbreak involving both horses and personnel in a veterinary teaching hospital in Israel. Since then, surveillance continued, and occasional MRSA isolation occurred. Two years later, MRSA of another spa type, t002, was isolated from a veterinarian and, 3 weeks later, from a horse. The appearance of spa type t002, a common clone in human medicine in Israel, among both personnel and horses, prompted a point-prevalence survey of hospital personnel and hospitalized horses. Fifty-nine staff members (n = 16 equine; n = 43, other) and 14 horses were screened. Ten of 59 staff members (16.9%) and 7 of 14 horses (50%) were MRSA carriers. Among the staff, 44% of large animal department (LAD) personnel, compared with only 7% of non-LAD personnel, were carriers. Isolates from all horses and from 9 of 10 personnel were found to be of MRSA spa type t002. This clone was later isolated from an infected postoperative wound in a hospitalized horse. Measures were taken to contain transmission between horses and personnel, as was done in the previous outbreak, resulting in reduction of transmission and, finally, cessation of cross-transmission between horses and personnel.

ACVIM consensus statement on therapeutic antimicrobial use in animals and antimicrobial resistance

The epidemic of antimicrobial resistant infections continues to challenge, compromising animal care, complicating food animal production and posing zoonotic disease risks. While the overall role of therapeutic antimicrobial use in animals in the development AMR in animal and human pathogens is poorly defined, veterinarians must consider the impacts of antimicrobial use in animal and take steps to optimize antimicrobial use, so as to maximize the health benefits to animals while minimizing the likelihood of antimicrobial resistance and other adverse effects. This consensus statement aims to provide guidance on the therapeutic use of antimicrobials in animals, balancing the need for effective therapy with minimizing development of antimicrobial resistance in bacteria from animals and humans.

Evaluation of regional limb perfusion with chloramphenicol using the saphenous or cephalic vein in standing horses

Regional limb perfusion (RLP) significantly decreases morbidity and mortality associated with distal limb injuries in horses. There is an urgent need for finding additional effective antimicrobial drugs for use in RLP. In this study, we tested the pharmacokinetics (PK) of chloramphenicol in RLP. Eight horses participated in the study, which was approved by the University Animal Care and Use Committee. The cephalic and the saphenous veins were used to perfuse the limbs. Synovial samples were collected from the metacarpo/metatarsophalangeal (MCP/MTP) joint. The Friedman Test was applied for assessing change in PK concentration over time, for all time points. The Wilcoxon Signed Ranks Test was used to test the difference between PK concentration in joint & serum as well as concentration in joint vs. MIC. The comparison of measurements between measurements taken on hind vs. front legs was carried out using the Mann-Whitney Test. A P-value of 5% or less was considered statistically significant. After RLP, the concentration of chloramphenicol in the synovial fluid of the MCP/MTP joint using either the cephalic or the saphenous vein was initially far above the minimal inhibitory concentration (MIC) of most susceptible pathogens and remained above the MIC for approximately 6 h. The results indicate that performing RLP using the cephalic and saphenous veins enables reaching concentrations of chloramphenicol in the MCP/MTP joint that are well above the MIC of most susceptible pathogens. The chloramphenicol concentrations achieved in the synovial fluid of the MCP/MTP joint in the current study were between 1.5 (MTP) and 7 (MCP) times the MIC of MRSA in horses. These results are encouraging since MRSA infections are becoming far more common, causing considerable morbidity. To the best of our knowledge, this is the first study to evaluate the pharmacokinetics of chloramphenicol following RLP in the horse and the results are positive.

Risk factors for MRSA infection in companion animals: results from a case-control study within Germany

Increasing numbers of companion animals suffering from infections with methicillin-resistant Staphylococcus aureus (MRSA) have been reported in the recent past. These infections are of particular concern because of the limited treatment options for MRSA and their transferability to humans. Since MRSA lineages isolated from infected companion animals often mirror typical human epidemic strains circulating in the same region, successful strategies to combat MRSA need strong and coordinated efforts from both, the human and the veterinary field according to the "One Health" concept. Hence, to identify potential risk factors related to MRSA infections in dogs, cats and horses, a case-control study was conducted, including data on 106 MRSA-infected animal patients as cases and 102 MSSA-infected animals as controls, originating from 155 different veterinary settings within Germany. Demographic data on animal patients, patient history and administration of antibiotics as well as practice/clinic specific parameters were assessed as putative risk factors. Multivariable logistic regression identified the following variables as risk factors for MRSA infection compared to MSSA infection: number of employees working at the veterinary setting (n>10; p<0.001), antibiotic treatment prior to sampling (systemic: p=0.002; local: p=0.049, both: p=0.011) and surgical site infection (p<0.001). Spa typing revealed predominantly clonal complexes well-known for hospital-associated lineages spreading in human health-care settings in Germany (CC5 and CC22) for isolates of dog and cat origin. CC398-MRSA dominated among equine isolates, a CC that was described as a nosocomial pathogen in equine clinical settings before. The identified risk factors and genotyping results are in accordance with numerous study outcomes from the field of human medicine and point towards reasonable problems with nosocomial spread of MRSA, especially within companion animal veterinary clinics. To define targeted infection control strategies against nosocomial pathogens, it is important to accomplish intervention studies addressing routes of transmission in companion animal veterinary settings.