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

Companion animals: a reservoir for methicillin-resistant Staphylococcus aureus in the community?

This article reviews the literature on the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in dogs, cats and horses. Over the past 10 years, MRSA has emerged as an important pathogen in veterinary medicine, especially in countries with a high MRSA burden in human hospitals. During the same period, community-associated MRSA (CA-MRSA) infections in humans without apparent links to healthcare facilities have increased dramatically. Although animal infections occur outside human hospitals, significant epidemiological, clinical and genetic differences exist between CA-MRSA in humans and the majority of MRSA infections in the different animal species. The recognition of MRSA in animals has raised concern over their role as potential reservoirs or vectors for human MRSA infection in the community. However, available data on MRSA transmission between humans and companion animals are limited and the public health impact of such transmission needs to be the subject of more detailed epidemiological studies.

Attempted eradication of methicillin-resistant Staphylococcus aureus colonisation in horses on two farms

REASONS FOR PERFORMING STUDY

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging equine and zoonotic pathogen. Infection control protocols can be used to control MRSA in human hospitals, but measures to eradicate MRSA on horse farms have not been evaluated.

OBJECTIVES

To describe an MRSA eradication programme that was used to attempt to eliminate MRSA colonisation among horses and horse personnel on 2 equine farms.

METHODS

Active surveillance cultures and infection control protocols were implemented on 2 farms with endemic MRSA.

RESULTS

Active screening and strict implementation of infection control protocols resulted in a rapid decrease in number of colonised horses on both farms. The majority of horses eliminated MRSA without antimicrobial treatment. On one farm colonisation was eradicated, while only 2 (3%) colonised horses remained on the other farm at the end of the study.

CONCLUSIONS

Although at this stage the benefit of eradication of MRSA from populations of horses and cost-benefit studies have not been established, this study illustrates that short-term eradication can be achieved with a policy of segregation, enhanced infection control precautions and repeated testing of groups of animals.

POTENTIAL RELEVANCE

Infection control practices should form the basis of MRSA control. Antimicrobial therapy does not appear to be required for eradication of MRSA colonisation in horses and control of MRSA on farms. In appropriate circumstances, these methods may be useful for controlling the spread of this potentially serious pathogen.

Emergence of methicillin-resistant Staphylococcus aureus (MRSA) in different animal species

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) in animals such as horses, pet animals and productive livestock has raised questions of a probable human origin and in more general of host specificity of S. aureus. Particular clonal lineages are obviously specific for humans (e.g. ST15, ST25, ST45) and other for ruminants (e.g. ST151). MRSA associated with veterinary nosocomial infections (e.g. ST8 and ST254 in horses, ST22 in small animals) very likely have their origin in health care facilities. MRSA ST398 which became first known from widespread colonization in industrially raised pigs seems to have a limited host specificity and is able to colonize and to cause infections in various hosts. Mechanisms of host adaptation and their genomic background are poorly understood so far.

Prevalence of methicillin-resistant Staphylococcus aureus colonization in horses in Saskatchewan, Alberta, and British Columbia

This study estimated the prevalence of methicillin resistant Staphylococcus aureus (MRSA) in nasal swabs of 458 horses in western Canada. The rate of colonization was 1.3% +/- 5.84% [95% confidence interval (CI)], a rate similar to those reported elsewhere. Colonization tended to be transient and seemed unrelated to stress or administration of antimicrobials. Five of the 6 isolates were Canadian epidemic MRSA-5, a human clone that appears to predominate in horses in North America. The other isolate was spa type 539 (t034), a sequence type 398 strain, and this is the first report of this clone in horses in North America. Surveillance is warranted because of the potential of MRSA to cause disease in horses and humans.

Heterogeneity among methicillin-resistant Staphylococcus aureus from Italian pig finishing holdings

A survey for methicillin-resistant Staphylococcus aureus (MRSA) in finishing pig holdings was carried out in Italy in 2008. MRSA isolates were characterised by spa-, MLST-, SCCmec- and antimicrobial susceptibility typing. A prevalence of 38% (45/118, 95% CI 29.4-46.9%) positive holdings was observed. Eleven different spa-types were found among 102 MRSA isolates, clustering in lineages associated with farm animals (ST398, ST9, ST(CC)97 in 36 holdings) and humans (ST1, 7 holdings). Nine (7.6%) holdings were positive for two, three or four different and unrelated spa-types in various combinations. ST398 was the most prevalent lineage (33 positive holdings). The most prevalent spa-type was t899 (ST398), detected in 22 positive holdings. Three novel spa-types (t4794 of ST9; t4795 of ST97; t4838 of ST398) were detected. Ten holdings were positive for spa-type t1730, that proved to be a new single-locus variant of ST97, within the CC97 (ST1476). The most prevalent SCCmec was Type V (79 isolates), while Type IVb was found in 10 isolates. None of the isolates was positive for Panton-Valentine Leukocidin, while most of the t127 and t1730 isolates, one t4794, one t4795, and one t2922 were positive for LukE-LukD genes. All 64 antimicrobial susceptibility tested isolates were resistant to tetracyclines, with high resistance rates to trimethoprim (68.8%), erythromycin (60.9%), and ciprofloxacin (35.4%). All t127, ST1 isolates were resistant to tetracycline-ciprofloxacin-erythromycin. This survey provides the first report of MRSA ST1 and ST(CC)97 among pigs and the first report of MRSA ST9 from pigs in Europe. The presence of human-associated CA-MRSA (t127, ST1, SCCmec type V) in 6% holdings surveyed can represent an additional MRSA reservoir for infections in humans.

A review of published reports regarding zoonotic pathogen infection in veterinarians

OBJECTIVE

To identify published reports regarding zoonotic pathogen infection among veterinarians.

DESIGN

Literature review.

PROCEDURES

The PubMed electronic database of medical literature published between 1966 and November 2007 was searched. Clinical case reports and reports of outbreak investigations were also identified through searches of the literature outside of PubMed and searches of references listed in included articles. Reports eligible for inclusion included controlled and uncontrolled studies examining seroprevalence of animal pathogens in veterinarians, serosurveys involving veterinarians, and reports of zoonotic pathogen infections causing clinical illness.

RESULTS

66 relevant articles were identified. This included 44 seroepidemiologic studies (some examined > 1 pathogen), 12 case reports, 3 outbreak investigations, and 7 self-reported surveys (including 4 related to personal protective equipment use). Of the 44 seroepidemiologic studies, 37 (84%) identified an increased risk of zoonotic pathogen infection among veterinarians, and 7 (16%) identified no increased risk or a decreased risk. Surveys also documented that veterinarians often failed to use recommended personal protective equipment.

CONCLUSIONS AND CLINICAL RELEVANCE

Our review indicated that veterinarians had an increased risk of infection with a number of zoonotic pathogens. It also suggested that veterinarians may inadvertently serve as biological sentinels for emerging pathogens and could potentially spread zoonotic pathogens to their families, community members, and the animals for which they provide care. Professional and policy measures should be implemented to reduce the risk that veterinarians will become infected with, or transmit, zoonotic pathogens.

Pets and antimicrobial resistance

Antimicrobial resistance is a growing problem and is a significant public health issue. An increasing number of organisms are developing resistance to many of the antimicrobial agents available for treatment of infections in both humans and animals. These resistant organisms often result in greater disease severity, longer hospitalization, and increased care and treatment costs. This article reviews the current situation of antimicrobial resistance in companion small animals and highlights how important it is for veterinarians to recognize the significance of antimicrobial resistance and to commit to the judicious use of antimicrobial agents.

Methicillin-resistant Staphylococcus aureus: a new zoonotic agent?

Staphylococcus aureus is a major cause of infection in hospitals and the community. One third of the general population is colonized by the bacterium, constituting a risk factor for acquisition of infection with this pathogen. Worldwide, the increasing antibiotic resistance of S. aureus complicates treatment of infection and control measures. Soon after the introduction of methicillin, the first isolates resistant to this antibiotic were reported and named methicillin-resistant S. aureus (MRSA). During the past decade a major change in MRSA epidemiology has been observed: whereas in the past MRSA was almost exclusively regarded a hospital pathogen, the advent of community-acquired MRSA has led to infections in people without hospital-related risk factors. Recent evidence has also identified a link between colonization of livestock and MRSA carriage and infections in people who work with animals. Screening of pigs and pig farmers in the Netherlands revealed high prevalence of MRSA sequence type (ST) 398 and it has become clear that the emergence of ST398 is not just a Dutch problem, as reports on livestock colonization and human infections are appearing worldwide. In Austria, the ST398 lineage has been detected in dust samples from pig breeding facilities and in food samples. Since the first Austrian detection of this emerging lineage in 2006, 21 human isolates, partially associated with infections, have been observed. MRSA has to be regarded as a new emerging zoonotic agent and livestock may constitute a growing reservoir of the ST398 lineage. More information is needed so that control measures to reduce the impact of the emerging MRSA ST398 lineage on public health can be developed and implemented.

Complications of equine wound management and dermatologic surgery

Complications of wounds and cosmetic surgery can be accurately managed with a combination of timely surgical and medical intervention to ensure the best possible outcome. The lack of soft tissue protection and a large quantity of susceptible synovial, tendon, ligament, and neurovascular structures make early and meticulous evaluation of limb wounds critical. Skin grafting is usually used following a period of open wound management and after healthy granulation tissue formation. Penetrating wounds of the abdomen or thorax have a guarded prognosis resulting from the ensuing potential for infection and pneumothorax. Gunshot wounds limited to the skeletal muscles have a good prognosis, whereas injuries that involve vital organs decreased survivability.

Methicillin-resistant Staphylococcus aureus and Staphylococcus pseudintermedius in veterinary medicine

Staphylococci are important opportunistic pathogens in most animal species. Among the most relevant species are the coagulase positive species Staphylococcus aureus and Staphylococcus pseudintermedius. Methicillin resistance has emerged as an important problem in both of these organisms, with significant concerns about animal and public health. The relative importance of these staphylococci on different animal species varies, as do the concerns about zoonotic transmission, yet it is clear that both present a challenge to veterinary medicine.

Clusters of infections in horses with MRSA ST1, ST254, and ST398 in a veterinary hospital

During 2006 and 2007 small clusters of methicillin-resistant Staphylococcus aureus (MRSA) infections in horses were recorded in different clinical departments of a veterinary university. The infections were caused by different MRSA clones (ST1, ST254, and ST398). In the same time, nasal colonization of veterinarians, veterinary personnel, and students was observed indicating transmission to humans.

Comparative molecular analysis substantiates zoonotic potential of equine methicillin-resistant Staphylococcus aureus

Despite the increasing importance of methicillin-resistant Staphylococcus aureus (MRSA) in veterinary medicine, knowledge about the epidemiology of the pathogen in horses is still poor. The phylogenetic relationship of strains of human and equine origins has been addressed before, usually by analyzing results of common standard classification methods for MRSA. This work intends to go beyond the baseline of typing procedures in order to comparatively characterize equine and human MRSA strains with similar phylogenetic backgrounds. In addition to multilocus sequence typing, pulsed-field gel electrophoresis, spa typing, staphylococcal cassette chromosome mec typing, and a PCR for Panton-Valentine leukocidin gene detection, a microarray analysis of a total of 185 structural, virulence-associated, and resistance loci was applied. The results showed that clonal complex 8 (CC8) was absolutely predominant (16 strains) in 19 investigated equine MRSA strains. Of the CC8 strains, 13 belonged to sequence type 254 (ST254) and the other 3 to ST8. This genotype has been isolated from different equine patients in various regions over several years, substantiating the apparent predominance of CC8 STs in MRSA strains of horses worldwide. Furthermore, comparatively investigated human strains of ST254 displayed molecular-typing results indistinguishable from those for strains of equine origin. Two further equine strains (ST22 and ST1117) showed similarity to ST22 human strains (CC22). One equine strain belonged to ST398, a genotype recently described as being frequently isolated from specimens from pigs and pig farmers. These data provide evidence for the adaptation of certain MRSA genotypes to more than one mammalian species, reflecting their extended host spectra.

Methicillin-resistant and -susceptible Staphylococcus aureus strains of clonal lineages ST398 and ST9 from swine carry the multidrug resistance gene cfr

Methicillin-resistant Staphylococcus aureus clonal lineage ST398 and methicillin-susceptible lineage ST9 strains have their main reservoir in swine but can colonize and cause infections in humans. The phenicol/lincosamide/oxazolidinone/pleuromutilin/streptogramin A multidrug resistance gene cfr was detected in isolates of both clonal lineages, rendering a spread to humans with exposure to swine farming possible.

Antimicrobial resistance in companion animals

Antimicrobial resistance (AMR) is an emerging problem in companion animals, because of difficult-to-treat infections, possible pressure to use antimicrobials that are important in human medicine, and potential zoonotic transmission. The extent and importance of AMR in companion animals are poorly understood, in part because of limited surveillance; however, it is clear that resistance is problematic in many pathogens and commensals, including staphylococci, enterococci, Escherichia coli and Salmonella.

Infection with Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus t034

Panton-Valentine leukocidin (PVL)–positive methicillin-resistant Staphylococcus aureus (MRSA), sequence type 398 is believed to be of animal origin. We report 2 cases of infection due to PVL–positive MRSA, spa type t034, in patients in Sweden who had had no animal contact.

Staphylococcus aureus host specificity: comparative genomics of human versus animal isolates by multi-strain microarray

Staphylococcus aureus is a commensal and pathogen of several mammalian species, particularly humans and cattle. We aimed to (i) identify S. aureus genes associated with host specificity, (ii) determine the relatedness of human and animal isolates, and (iii) identify whether human and animal isolates typically exchanged mobile genetic elements encoding virulence and resistance genes. Using a well-validated seven-strain S. aureus microarray, we compared 56 UK S. aureus isolates that caused infection in cows, horses, goats, sheep and a camel with 161 human S. aureus isolates from healthy carriers and community acquired infections in the UK. We had previously shown that human isolates are clustered into ten dominant and a few minor lineages, each with unique combinations of surface proteins predicted to bind to human proteins. We found that the animal-associated S. aureus clustered into ten lineages, with 61 % assigned to four lineages, ST151, ST771, ST130 and ST873, that were unique to animals. The majority of bovine mastitis was caused by isolates of lineage ST151, ST771 and ST97, but a few human lineages also caused mastitis. S. aureus isolated from horses were more likely to cluster into human-associated lineages, with 54 % of horse-associated S. aureus assigned to the human clusters CC1, CC8 and CC22; along with the presence of some multi-drug resistant strains, this suggests a human origin. This is the most comprehensive genetic comparison of human versus animal S. aureus isolates conducted, and because we used a whole-genome approach we could estimate the key genes with the greatest variability that are associated with host specificity. Several genes conserved in all human isolates were variable or missing in one or more animal lineages, including the well-characterized lineage specific genes fnbA, fnbB and coa. Interestingly, genes carried on mobile genetic elements (MGEs) such as chp, scn and sak were less common in animal S. aureus isolates, and bap was not found. There was a lot of MGE variation within lineages, and some evidence that exchange of MGEs such as bacteriophage and pathogenicity islands between animal and human lineages is feasible, but there was less evidence of antibiotic resistance gene transfer on the staphylococcal cassette chromosomes (SCC) or plasmids. Surprisingly, animal lineages are closely related to human lineages and only a handful of genes or gene combinations may be responsible for host specificity.

Staphylococcus aureus colonization in healthy horses in Atlantic Canada

Methicillin-resistant Staphylococcus aureus (MRSA) colonization was not identified in any of 497 horses from Atlantic Canada. Methicillin-susceptible S. aureus (MSSA) was isolated from a subsample of 19/242 (7.9%) horses. Colonization with MSSA is relatively common in healthy horses in Atlantic Canada, but MRSA is currently rare or absent.

Sequence analysis of the variable number tandem repeat in Staphylococcus aureus protein A gene: spa typing

The analyses of numerous prokaryotic and eukaryotic genomes have revealed the presence of variable number tandem repeats (VNTRs). VNTR analysis is currently widely used to sub-speciate many bacterial, fungal, and viral pathogens and has facilitated a number of molecular epidemiology studies. In this chapter, we focus on spa typing which is based on sequence analysis of VNTRs in the polymorphic X region of the Staphylococcus aureus protein A gene Staphylococcus aureus. As the specific methods for spa typing, detailed in this chapter, are well-established and routine procedures (e.g., DNA isolation, PCR and DNA sequencing) for most molecular biology laboratories, we highlight the analytic methods used to interpret the genotyping data generated by sequence analysis and their potential applications in local and global epidemiologic investigations.

Emergence of methicillin-resistant Staphylococcus aureus of animal origin in humans

MRSA from an animal reservoir has recently entered the human population and is now responsible for >20% of all MRSA in the Netherlands.

In 2003 in the Netherlands, a new methicillin-resistant Staphylococcus aureus (MRSA) strain emerged that could not be typed with Sma1 pulsed-field gel electrophoresis (NT-MRSA). The association of NT-MRSA in humans with a reservoir in animals was investigated. The frequency of NT-MRSA increased from 0% in 2002 to >21% after intensified surveillance was implemented in July 2006. Geographically, NT-MRSA clustered with pig farming. A case–control study showed that carriers of NT-MRSA were more often pig or cattle farmers (pig farmers odds ratio [OR] 12.2, 95% confidence interval [CI] 3.1–48.6; cattle farmers OR 19.7, 95% CI 2.3–169.5). Molecular typing showed that the NT-MRSA strains belonged to a new clonal complex, ST 398. This study shows that MRSA from an animal reservoir has recently entered the human population and is now responsible for >20% of all MRSA in the Netherlands.

Methicillin-resistant Staphylococcus aureus (MRSA) strain ST398 is present in midwestern U.S. swine and swine workers

BACKGROUND

Recent research has demonstrated that many swine and swine farmers in the Netherlands and Canada are colonized with MRSA. However, no studies to date have investigated carriage of MRSA among swine and swine farmers in the United States (U.S.).

METHODS

We sampled the nares of 299 swine and 20 workers from two different production systems in Iowa and Illinois, comprising approximately 87,000 live animals. MRSA isolates were typed by pulsed field gel electrophoresis (PFGE) using SmaI and EagI restriction enzymes, and by multi locus sequence typing (MLST). PCR was used to determine SCCmec type and presence of the pvl gene.

RESULTS

In this pilot study, overall MRSA prevalence in swine was 49% (147/299) and 45% (9/20) in workers. The prevalence of MRSA carriage among production system A's swine varied by age, ranging from 36% (11/30) in adult swine to 100% (60/60) of animals aged 9 and 12 weeks. The prevalence among production system A's workers was 64% (9/14). MRSA was not isolated from production system B's swine or workers. Isolates examined were not typeable by PFGE when SmaI was used, but digestion with EagI revealed that the isolates were clonal and were not related to common human types in Iowa (USA100, USA300, and USA400). MLST documented that the isolates were ST398.

CONCLUSIONS

These results show that colonization of swine by MRSA was very common on one swine production system in the midwestern U.S., suggesting that agricultural animals could become an important reservoir for this bacterium. MRSA strain ST398 was the only strain documented on this farm. Further studies are examining carriage rates on additional farms.

Transmission of methicillin-resistant Staphylococcus aureus strains between different kinds of pig farms

The main objective of the present study was to investigate if different kinds of pig farms, like farrowing farms and rearing farms, play a role in the transmission of methicillin-resistant Staphylococcus aureus (MRSA) to Dutch finishing farms. Twelve farrowing farms, 11 finishing farms, 6 farrow-to finish farms, 1 rearing farm and 1 centre for artificial insemination were included. Screening of 310 pigs from these 31 farms showed 35 pigs (11%) to carry MRSA in their nares. On 7 of the 31 (23%) investigated farms colonized pigs were found, including 3 finishing farms, 3 farrowing farms and 1 farrow-to-finish farm. The use of standard antimicrobial medication of the pigs seemed to be a risk factor for MRSA carriage. Screening of the pigs on six farms supplying pigs for the MRSA positive farms revealed that the pigs on all but one farm were MRSA positive. Genotyping revealed that all MRSA strains were non-typeable by PFGE using the SmaI restriction enzyme and had multilocus sequence type (MLST) ST398. Different spa-types were found including t011, t108, t567, t899 and t1939, but the spa-types on epidemiologically related farms were identical indicating that MRSA are transmitted between farms through the purchase of colonized pigs. Two SCCmec types were found among the MRSA: type IV and type V. SCCmec type V was predominant. On two farms MRSA isolates with ST398, the same spa-type but with different SCCmec types (IV and V) were found, suggesting that different SCCmec elements have been inserted into MSSA with the same genotype. All MRSA strains were resistant to tetracycline, but additional resistances to erythromycin, lincomycin, kanamycin and gentamicin were also found. All MRSA isolates were negative for the exfoliative toxin genes (eta and etb), PVL toxin genes (lukF and lukS), toxic shock syndrome gene (tst-1), and the leukotoxin genes (lukE, lukD, lukM, lukF').

Meticillin-resistant Staphylococcus aureus in animals: A review

The objectives of this paper are to review published data on the prevalence and epidemiology of meticillin-resistant Staphylococcus aureus (MRSA) infection and colonization in animals and to provide suggestions for preventing and controlling the problem in veterinary practice. MRSA first emerged as a serious pathogen in human medicine during the late 1970s and has been increasingly reported in animals during the past 10 years. The prevalence of MRSA in human infections varies markedly between geographical areas, being as high as 60% in parts of the USA, 40% in southern Europe but <1% in northern Europe. Epidemiological evidence, including phenotypic and molecular typing data, suggests that MRSA isolates from dogs and cats are indistinguishable from human healthcare isolates, whereas strains of MRSA isolated from horses and associated personnel are different. There is evidence that transfer of MRSA strains can occur between animals and humans and vice versa. Guidelines for the control of MRSA in animals have been drawn up by individual institutions based on those available for human MRSA infection. Risk factors for MRSA infection in animals are currently under investigation and such data are essential for the preparation of specific guidelines for control of MRSA in veterinary practice.

Methicillin-resistant staphylococcal colonization in dogs entering a veterinary teaching hospital

Nasal, axillary and rectal swabs were collected from 193 dogs admitted to the Ontario Veterinary College Veterinary Teaching Hospital. Enrichment culture was performed and coagulase positive staphylococci were identified via standard methods. Methicillin-resistant Staphylococcus pseudintermedius was isolated from 4/193 (2.1%) dogs, and methicillin-resistant Staphylococcus aureus and methicillin-resistant Staphylococcus schleiferi subsp. coagulans were each isolated from 1/193 (0.5%) dogs. Methicillin-resistant Staphylococcus intermedius was not identified. All S. pseudintermedius isolates were unrelated on pulsed-field gel electrophoresis. Evaluation of the epidemiology of methicillin-resistant staphylococcal colonization is necessary to understand the apparent emergence of these strains and to develop appropriate control strategies.

Phylogenetic analysis of livestock oxacillin-resistant Staphylococcus aureus

The aim of this study was to characterize oxacillin-resistant Staphylococcus aureus (ORSA) isolates from livestock environments and meat market workers by molecular epidemiological analysis. Staphylococcal enterotoxin reversed passive latex agglutination (RPLA) and multiplex polymerase chain reactions (PCR) were used to detect enterotoxin-producing S. aureus. The molecular genetic similarity of ORSA was also compared by pulse-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). A total of 30 ORSA isolates were identified and 27 of these strains were from human sources-a higher contamination potential from human origin in the animal raising and handling field was suspected. The most common type of enterotoxin detected in this study was type B. Regarding the bacterial phylogenetic analysis of ORSA isolates, five major clusters of PFGE patterns were suggested with >80% similarity in cluster I. Seven MLST patterns were identified with the most prevalent types being ST338/ST338(slv) and ST59. Population genetic studies based on MLST have shown that major ORSA clones have emerged from six clonal complexes (CCs), with CC59 being the dominant one. In conclusion, a high prevalence of ORSA with enterotoxin type B as well as ST59 and ST338/ST338(slv) colonization was observed among livestock with human origins in this study. We suggest further tracking and comparing of the epidemiological evidence of community-acquired and hospital-acquired ORSA in human living environments and livestock-producing environments.

New antimicrobials, systemic distribution, and local methods of antimicrobial delivery in horses

The local delivery of antimicrobials is a valuable therapeutic tool with a low morbidity, is practical to use, and is well tolerated by horses. Clinically, its use has allowed equine practitioners to achieve better results when treating musculoskeletal infections, and it represents an extremely useful tool in the practitioner's armamentarium against these types of infections. The technique is indicated to combat orthopedic infections involving bones, joints, physes, tendon sheaths, and foot tissues. Optimal treatment must include other approaches, such as systemic antimicrobial therapy and surgical debridement and lavage, and monitoring of the clinical progression of the patient can help to determine the ideal protocol for each patient.

Prevalence of methicillin-resistant Staphylococcus aureus among veterinarians: an international study

Pig farmers and veterinarians in contact with livestock in The Netherlands have a higher risk of methicillin-resistant Staphylococcus aureus (MRSA) carriage than the general population. The objective of this study was to investigate whether this is also true for other professionals in contact with pigs in an international setting. A convenience sample of 272 participants at an international conference on pig health in Denmark was screened for MRSA carriage using combined nose/throat swabs and were asked to complete a questionnaire concerning animal contacts, exposure to known MRSA risk-factors, and the protective measures taken when entering pig farms. In total, 34 (12.5%) participants from nine countries carried MRSA. Thirty-one of these isolates were non-typeable by pulsed-field gel electrophoresis following SmaI digestion of chromosomal DNA. All of the non-typeable isolates belonged to spa types (t011, t034, t108, t571, t567 and t899) that correspond to multilocus sequence type 398. All of the above-mentioned spa types, with the exception of t899, have been isolated previously from either Dutch pigs, pig farmers and/or veterinarians. Protective measures, e.g., masks, gowns and gloves, did not protect against MRSA acquisition. Transmission of MRSA from pigs to staff tending to these animals appears to be an international problem, creating a new reservoir for community-acquired MRSA (CA-MRSA) in humans in Europe, and possibly worldwide. The rise of a new zoonotic source of MRSA could have a severe impact on the epidemiology of CA-MRSA, and may have consequences for the control of MRSA, especially in those countries that maintain a low prevalence by means of search-and-destroy policies.

Methicillin resistant Staphylococcus aureus colonization in pigs and pig farmers

Methicillin resistant Staphylococcus aureus (MRSA) colonization has recently been identified in pigs and people that work with pigs, raising concerns about the role of pigs as reservoirs of MRSA for human infection. The objectives of this study were to evaluate the prevalence of MRSA colonization in pigs and pig farmers in Ontario, Canada and to characterize MRSA strains. Nasal and rectal swabs were collected from 285 pigs from three different age groups from 20 pig farms. Nasal swabs were collected from farm personnel and a brief questionnaire was also administered. The prevalence of MRSA colonization in farms was 45% (9/20) whereas the prevalence in pigs was 24.9% (71/285). There was no difference in MRSA colonization between age groups. The prevalence of MRSA colonization in pig farmers was 20% (5/25). There was a correlation between the presence of MRSA in pigs and humans on farms (P value=0.001). The results of spa typing revealed the predominant strain in pigs and humans was eGenomics spa type 539 (Ridom t034, clonal complex 398) which accounted for 59.2% of isolates and has been reported in pigs in Europe. A common human epidemic clone, CMRSA-2 (USA100, clonal complex 5) was also found in both pigs and pig personnel. Indistinguishable strains were found in pigs and pig personnel on all five farms with a colonized human. This study demonstrates that MRSA is common in pigs in Ontario, Canada, and provides further support to concerns about transmission of MRSA between pigs and humans.

Treatment of community-associated methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus has emerged in the community among patient populations without traditional antibiotic resistance risk factors and is causing a variety of clinical syndromes, in particular skin and soft tissue infections. These infections can range from minor skin involvement that can be treated in an outpatient setting to more serious infections such as necrotizing fasciitis requiring hospitalization. Inpatient and outpatient healthcare providers must be aware of the treatment, prevention, and infection control practices for this emerging pathogen.

Risk factors for methicillin-resistant Staphylococcus aureus colonization in horses admitted to a veterinary teaching hospital

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging problem in horses; however, the epidemiology of infection and colonization is poorly understood. This study evaluated factors associated with MRSA colonization at the time of admission to a veterinary teaching hospital. A case-control study evaluating historical factors was performed. Previous colonization of the horse, previous identification of colonized horses on the farm, antimicrobial administration within 30 days, admission to the neonatal intensive care unit, and admission to a service other than the surgical service were risk factors for community-associated colonization. A better understanding of risk factors for MRSA colonization is important to elucidate the epidemiology of this emerging veterinary and zoonotic pathogen, and to design evidence-based infection control programs.

Occupational risks during a monkeypox outbreak, Wisconsin, 2003

We determined factors associated with occupational transmission in Wisconsin during the 2003 outbreak of prairie dog--associated monkeypox virus infections. Our investigation included active contact surveillance, exposure-related interviews, and a veterinary facility cohort study. We identified 19 confirmed, 5 probable, and 3 suspected cases. Rash, headache, sweats, and fever were reported by > 80% of patients. Occupationally transmitted infections occurred in 12 veterinary staff, 2 pet store employees, and 2 animal distributors. The following were associated with illness: working directly with animal care (p = 0.002), being involved in prairie dog examination, caring for an animal within 6 feet of an ill prairie dog (p = 0.03), feeding an ill prairie dog (p = 0.002), and using an antihistamine (p = 0.04). Having never handled an ill prairie dog (p = 0.004) was protective. Veterinary staff used personal protective equipment sporadically. Our findings underscore the importance of standard veterinary infection-control guidelines.

Investigation of meticillin-resistant Staphylococcus aureus in pigs used for research

Meticillin-resistant Staphylococcus aureus (MRSA) was unexpectedly isolated from a pig used for streptozotocin-induced diabetes research. To investigate the possible source of the MRSA isolate, nasal swabs were obtained from the animal herd, and from animal holding rooms, and veterinary and research staff involved in the handling of the animals. Overall, four MRSA isolates were cultured from three pigs and from a clinician/scientist. Two were ST22-MRSA-IV, a human strain type associated with epidemic spread. The other two were ST398-MRSA-V, a strain type associated with pigs. Thus, care should be taken to prevent cross-transmission of MRSA.

Methicillin-resistant Staphylococcus aureus ST398 in humans and animals, Central Europe

Methicillin-resistant Staphylococcus aureus of clonal lineage ST398 that exhibits related spa types and contains SCCmec elements of types IVa or V has been isolated from colonized and infected humans and companion animals (e.g., dog, pig, horse) in Germany and Austria. Of particular concern is the association of these cases with cases of nosocomial ventilator-associated pneumonia.

Methicillin-resistant Staphylococcus aureus in veterinary doctors and students, the Netherlands

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in the Netherlands, at 1.0%, is among the lowest in Europe. In 2004, a relationship between pig farming and a high risk for MRSA carriage was found. To investigate if those in professional contact with livestock are at higher risk for MRSA carriage, we screened 80 veterinary students and 99 veterinarians and questioned them about animal contacts and known MRSA risk factors. Of these, 27 students who did not have livestock contact were excluded from further analysis. We found 7 carriers of MRSA, a prevalence of 4.6%, which is similar to that found in patients who had previously been treated at foreign hospitals. A correlation of MRSA carriage with a specific animal group could not be established. To preserve the low prevalence of MRSA in the Netherlands, persons involved in the care of livestock should be isolated and screened on admission to the hospital.

Methicillin-resistant Staphylococcus pseudintermedius in a veterinary teaching hospital

We surveyed methicillin-resistant coagulase-positive staphylococcus (MRCPS) strains from 57 (26 inpatient and 31 outpatient) dogs and 20 veterinary staff in a veterinary teaching hospital. From the staff, three MRCPS strains were isolated, and two were methicillin-resistant Staphylococcus aureus (MRSA). In contrast, 18 MRCPS strains were detected in both inpatient (12 of 26 [46.2%]) and outpatient (6 of 31 [19.4%]) dogs. Among them, only one strain was MRSA. Using direct sequencing of sodA and hsp60 genes, the 18 MRCPS strains other than MRSA from a staff and 17 dogs, were finally identified as Staphylococcus pseudintermedius, a novel species of Staphylococcus from a cat. All of the methicillin-resistant S. pseudintermedius (MRSP) strains were multidrug resistant to erythromycin, clindamycin, trimethoprim-sulfamethoxazole, and levofloxacin. Most of the MRSP strains showed high-level resistance to oxacillin (>/=128 mug/ml, 15 of 18 [83.3%]), and 10 of 15 (66.7%) high-level oxacillin-resistant MRSP strains carried type III SCCmec. DNA fingerprinting of MRSP strains by pulsed-field gel electrophoresis yielded eight clusters: clone A with four subtypes, clone B with four subtypes, clone C with three subtypes, and five other different single clones. MRSP strains from the staff and some inpatient and outpatient dogs shared three major clones (clones A, B, and C), but the strains of the other five different clusters were distributed independently among inpatient or outpatient dogs. This genetic diversity suggested that the MRSP strains were not only acquired in this veterinary teaching hospital but also acquired in primary veterinary clinics in the community. To our knowledge, this is the first report of MRSP in dogs and humans in a veterinary institution.

International dissemination of a high virulence rabbit Staphylococcus aureus clone

High virulence rabbit Staphylococcus aureus strains cause chronic and spreading problems of mastitis, pododermatitis and subcutaneous abscesses on rabbit flock level, whereas infections with low virulence strains are limited to individual rabbits. In the present report, 13 high virulence rabbit S. aureus strains, selected out of a large collection of strains isolated in five European countries between 1983 and 2004, were genotyped using pulsed-field gel electrophoresis, spa typing, multilocus sequence typing (MLST) and accessory gene regulator (agr) group typing. Two low virulence rabbit S. aureus strains were also included in the study. The results indicate the clonal origin of high virulence rabbit S. aureus strains present in Europe. Furthermore, the results of MLST and spa typing form a basis for international epidemiology of rabbit S. aureus strains, as these DNA sequence-based typing techniques can easily be used for intercentre comparisons.

Occurrence, species distribution, antimicrobial resistance and clonality of methicillin- and erythromycin-resistant staphylococci in the nasal cavity of domestic animals

beta-Lactams and macrolides are important antibiotics for treatment of staphylococcal infections in both humans and animals. The aim of the study was to investigate the occurrence, species distribution and clonality of methicillin- and erythromycin-resistant staphylococci in the nasal cavity of dogs, horses, pigs, and cattle in Denmark. Nasal swabs were collected from a total of 400 animals, including 100 individuals of each species. Methicillin- and erythromycin-resistant staphylococci were isolated on selective media, identified by 16S rDNA sequencing, and typed by pulsed field gel electrophoresis (PFGE). Methicillin-resistant coagulase-negative staphylococci (MRCoNS) harbouring mecA were isolated from horses (50%) and dogs (13%), but not from food animals. The species identified were S. haemolyticus (n=21), S. vitulinus (n=19), S. sciuri (n=13), S. epidermidis (n=8), and S. warneri (n=2). mecA-mediated methicillin resistance in S. vitulinus was described for the first time. Methicillin-resistant S. aureus was not detected. PFGE analysis revealed the presence of specific MRCoNS clones in samples originating from the same veterinary hospital or equine farm. Erythromycin-resistant S. aureus (ERSA) was detected in 38% of pigs and all isolates harboured a constitutively expressed erm(C) gene. The vast majority (37/38) of pigs carrying ERSA originated from a farm characterized by frequent use of macrolides. Most ERSA isolates (28/38) displayed indistinguishable or closely related PFGE patterns, indicating clonal distribution within the farm. Based on the analysis of data on antimicrobial consumption, the occurrence of MRCoNS in companion animals and that of ERSA in pigs reflected national and local patterns of antimicrobial usage.

Methicillin-resistant staphylococcal colonization in clinically normal dogs and horses in the community

AIMS

To evaluate the prevalence of methicillin-resistant staphylococcal (MRS) colonization in clinically normal dogs and horses in the community.

METHODS AND RESULTS

Three hundred clinically normal horses and 200 clinically normal dogs were enrolled. One nasal swab was collected from each horse. Two swabs were taken from each dog: (i) from an anterior nare, and (ii) a combination of the perineal area and 0.5 cm into the anus. Enrichment cultures were performed. Methicillin-resistant Staphylococcus aureus (MRSA) was not identified. Methicillin-resistant Staphylococcus intermedius (MRSI) was isolated from the nasal swab from three dogs. Methicillin-resistant coagulase negative staphylococci (MRCoNS) were isolated from 126/300 (42%) horses and 26/200 (13%) dogs.

CONCLUSIONS

At present MRSI is not considered to be a significant zoonotic concern; however, it may become an important pathogen in dogs. MRCoNS mostly cause disease in compromised human or animal hosts. However, these bacteria can serve as reservoirs of resistance determinants in the community, which could lead to the emergence of novel MRSA strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report of the prevalence of MRS colonization in clinically normal dogs in a community setting. Continued surveillance is indicated to determine whether MRSA will emerge in the animal population and become a concern for animal disease and zoonotic infection.