Livestock associated MRSA (LA-MRSA) and its relevance for humans in Germany

Livestock-associated meticillin-resistant Staphylococcus aureus (MRSA) among human MRSA isolates, European Union/European Economic Area countries, 2013

Currently, surveillance of livestock-associated meticillin-resistant Staphylococcus aureus (LA-MRSA) in humans in Europe is not systematic but mainly event-based. In September 2014, the European Centre for Disease Prevention and Control (ECDC) initiated a questionnaire to collect data on the number of LA-MRSA from human samples (one isolate per patient) from national/regional reference laboratories in European Union/European Economic Area (EU/EEA) countries in 2013. Identification of LA-MRSA as clonal complex (CC) 398 by multilocus sequence typing (MLST) was preferred, although surrogate methods such as spa-typing were also accepted. The questionnaire was returned by 28 laboratories in 27 EU/EEA countries. Overall, LA-MRSA represented 3.9% of 13,756 typed MRSA human isolates, but it represented ≥ 10% in five countries (Belgium, Denmark, Spain, the Netherlands and Slovenia). Seven of the reference laboratories did not type MRSA isolates in 2013. To monitor the dispersion of LA-MRSA and facilitate targeted control measures, we advocate periodic systematic surveys or integrated multi-sectorial surveillance.

MRSA in persons not living or working on a farm in a livestock-dense area: prevalence and risk factors

Objectives

MRSA emerged in livestock and persons in contact with livestock is referred to as livestock-associated MRSA (LA-MRSA). We assessed the prevalence and risk factors for MRSA carriage in persons not living or working on a farm.

Methods

A cross-sectional study was performed among 2492 adults living in close proximity of livestock farms. Persons working and/or living on farms were excluded. Nasal swabs were cultured using selective media. Participants completed questionnaires and the distance from the residential address to the nearest farm was calculated. The Mann-Whitney U -test was used to compare median distances. Risk factors were explored with logistic regression.

Results

Fourteen persons carried MRSA (0.56%; 95% CI 0.32%-0.92%), 10 of which carried LA-MRSA of multiple-locus variable-number tandem repeat analysis complex (MC) 398 (0.40%; 95% CI 0.20%-0.71%). MRSA MC 398 carriers lived significantly closer to the nearest farm than non-carriers (median: 184 versus 402 m; P  <   0.01). In bivariate analyses correcting for contact with livestock, this difference remained significant.

Conclusions

Although the prevalence was low, living near farms increased the risk of MRSA MC 398 carriage for persons not living or working on a farm. Further research is necessary to identify the transmission routes.

Review of Nonfoodborne Zoonotic and Potentially Zoonotic Poultry Diseases

Emerging and re-emerging diseases are continuously diagnosed in poultry species. A few of these diseases are known to cross the species barrier, thus posing a public health risk and an economic burden. We identified and synthesized global evidence for poultry nonfoodborne zoonoses to better understand these diseases in people who were exposed to different poultry-related characteristics (e.g., occupational or nonoccupational, operational types, poultry species, outbreak conditions, health status of flocks). This review builds on current knowledge on poultry zoonoses/potentially zoonotic agents transmitted via the nonfoodborne route. It also identifies research gaps and potential intervention points within the poultry industry to reduce zoonotic transmission by using various knowledge synthesis tools such as systematic review (SR) and qualitative (descriptive) and quantitative synthesis methods (i.e., meta-analysis). Overall, 1663 abstracts were screened and 156 relevant articles were selected for further review. Full articles (in English) were retrieved and critically appraised using routine SR methods. In total, eight known zoonotic diseases were reviewed: avian influenza (AI) virus (n = 85 articles), Newcastle disease virus (n = 8), West Nile virus (WNV, n = 2), avian Chlamydia (n = 24), Erysipelothrix rhusiopathiae (n = 3), methicillin-resistant Staphylococcus aureus (MRSA, n = 15), Ornithonyssus sylvarium (n = 4), and Microsporum gallinae (n = 3). In addition, articles on other viral poultry pathogens (n = 5) and poultry respiratory allergens derived from mites and fungi (n = 7) were reviewed. The level of investigations (e.g., exposure history, risk factor, clinical disease in epidemiologically linked poultry, molecular studies) to establish zoonotic linkages varied across disease agents and across studies. Based on the multiple outcome measures captured in this review, AI virus seems to be the poultry zoonotic pathogen that may have considerable and significant public health consequences; however, epidemiologic reports have only documented severe human cases clustered in Asia and not in North America. In contrast, avian Chlamydia and MRSA reports clustered mainly in Europe and less so in North America and other regions. Knowledge gaps in other zoonoses or other agents were identified, including potential direct (i.e., nonmosquito-borne) transmission of WNV from flocks to poultry workers, the public health and clinical significance of poultry-derived (livestock-associated) MRSA, the zoonotic significance of other viruses, and the role of poultry allergens in the pathophysiology of respiratory diseases of poultry workers. Across all pathogens reviewed, the use of personal protective equipment was commonly cited as the most important preventive measure to reduce the zoonotic spread of these diseases and the use of biosecurity measures to reduce horizontal transmission in flock populations. The studies also emphasized the need for flock monitoring and an integrated approach to prevention (i.e., veterinary-public health coordination with regard to diagnosis, and knowledge translation and education in the general population) to reduce zoonotic transmission.

Emergence and Spread of Antimicrobial Resistance: Recent Insights from Bacterial Population Genomics

Driven by progress of DNA sequencing technologies, recent population genomics studies have revealed that several bacterial pathogens constitute 'measurably evolving populations'. As a consequence, it was possible to reconstruct the emergence and spatial spread of drug-resistant bacteria on the basis of temporally structured samples of bacterial genome sequences. Based on currently available data, some general inferences can be drawn across different bacterial species as follows: (1) Resistance to various antibiotics evolved years to decades earlier than had been anticipated on the basis of epidemiological surveillance data alone. (2) Resistance traits are more rapidly acquired than lost and commonly persist in bacterial populations for decades. (3) Global populations of drug-resistant pathogens are dominated by very few clones, yet the features enabling such spreading success have not been revealed, aside from antibiotic resistance. (4) Whole-genome sequencing proved very effective at identifying bacterial isolates as parts of the same transmission networks.

Molecular Characteristics of Staphylococcus aureus Causing Bovine Mastitis between 2014 and 2015

Staphylococcus aureus is highly pathogenic and can cause diseases in both humans and domestic animals. In animal species, including ruminants, S. aureus may cause severe or sub-clinical mastitis. This study aimed to investigate the molecular profile, antimicrobial resistance, and genotype/phenotype correlation of 212 S. aureus isolates recovered from cases of bovine mastitis from 2014 to 2015 in the Shanghai and Zhejiang areas of China. Nineteen sequence types (STs) were determined by multi-locus sequence typing, while the dominant ST was ST97, followed by ST520, ST188, ST398, ST7, and ST9. Within 14 methicillin-resistant S. aureus (MRSA) isolates and 198 methicillin-susceptible S. aureus (MSSA) isolates, ST97 was the predominant MSSA clone and ST9-MRSA-SCCmecXII-spa t899 was the most common MRSA clone. The MRSA strains showed much higher rates of resistance to multiple antibiotics than did MSSA strains. Compared with other MSSA strains, MSSA ST398 was more resistant to clindamycin, erythromycin, and ciprofloxacin. No isolates were resistant to vancomycin, teicoplanin, or linezolid. The molecular profiles of the virulence genes varied in different strains. ST520 strains carried seg-sei-sem-sen-seo genes, and ST9 and ST97 harbored sdrD-sdrE genes. Virulence phenotype analysis showed diversity in different clones. Biofilm formation ability was significantly enhanced in ST188 and ST7, and red blood cell lysis capacity was relatively strong in all S. aureus strains of animal origin except ST7. Our results indicate that MSSA was the predominant S. aureus strain causing bovine mastitis in eastern regions of China. However, the presence of multidrug resistant and toxigenic MRSA clone ST9 suggests that comprehensive surveillance of S. aureus infection should be implemented in the management of animal husbandry products.

Current methodologies on genotyping for nosocomial pathogen methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen in hospitals and the community. As the rapid spread and wide distribution of antimicrobial resistance (such as MRSA), treatment for infectious diseases caused by microorganisms has become a vital threat. Thus, early identification and genotyping are essential for further therapeutic treatment and the control of rapid expansion of MRSA. In combination with applications and data feedbacks, this review focused on the currently available molecular-based assays on their utility and performance for rapid typing of MRSA, especially on effective molecular-based methods. Besides, a common mobile element SCCmec and prevalence of HA-MRSA, LA-MRSA and CA-MRSA were introduced in this review in order to provide a more complete profile of MRSA.

Characterisation of Staphylococcus aureus isolated from meat processing plants – a preliminary study

Introduction: Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) belonging to the clonal complex 398 (CC398) emerged recently in livestock as a new type of MRSA, which may cause zoonotic infections. This study presents data on the characterisation of S. aureus isolated from the meat processing plants. Material and Methods: S. aureus was isolated from 90 samples collected in the raw meat warehouse, from devices and surfaces of meat processing plants, and from finished meat products. The isolates were subjected to molecular analysis in order to investigate the presence of enterotoxin genes, the mecA gene, and to verify whether they belong to the clonal complex 398. The genetic relatedness of the isolates was determined using pulsed-field electrophoresis. Likewise, antimicrobial susceptibility was tested. Results: From 21 S. aureus strains isolated, five belonged to the CC398, two of which were recognised as MRSA and three as methicillin-sensitive Staphylococcus aureus (MSSA). The most prevalent enterotoxin genes were seg and sei. Two MRSA CC398 isolates, three MSSA CC398, and one MSSA were classified as multidrug-resistant. Conclusion: The first isolation of MSSA CC398 from beef in Poland indicates contamination of beef by strains belonging to this clonal complex. The occurrence of multidrug-resistant enterotoxigenic S. aureus isolates in the finished meat products constitutes a potential risk for the consumers.

Multilocus sequence typing and CTX-M characterization of ESBL-producing E. coli: a prospective single-centre study in Lower Saxony, Germany

The increasing prevalence of extended-spectrum β-lactamase (ESBL)-producing Gram-negative bacteria is a serious threat for current healthcare settings. In this study we investigated the molecular epidemiology of ESBL-producing E. coli at the University Medical Center Göttingen in Lower Saxony, Germany. All E. coli isolates with an ESBL phenotype were collected during a 6-month period in 2014. Multilocus sequence typing and CTX-M characterization were performed on 160 isolates. Of the ESBL-producing isolates 95·6% were CTX-M positive. Compared to recent Germany-wide studies, we found CTX-M-1 to occur in higher frequency than CTX-M-15 (44·4% vs. 34·4%). CTX-M-14 and CTX-M-27 were detected at 9·4% and 5·0%, respectively. The globally dominant sequence type (ST) 131, which is often associated with CTX-M-15, occurred at a relatively low rate of 24%. Major non-ST131 sequence types were ST101 (5%), ST58 (5%), ST10 (4·4%), ST38 (4·4%), ST410 (3·8%) and ST453 (3·1%). Several of these major sequence types were previously shown to be associated with livestock farming. Together, our study indicates that E. coli lineage distribution in individual healthcare settings can significantly differ from average numbers obtained in nationwide studies.

Antimicrobial resistances and virulence markers in Methicillin-resistant Staphylococcus aureus from broiler and turkey: A molecular view from farm to fork

Little is known about the characteristics of MRSA occurring along the broiler and turkey production chains. The aim of this study was to characterise and compare MRSA of turkey and broiler origin sampled on different production levels using a DNA microarray and antimicrobial susceptibility testing. Main differences could be observed in the prevalence of the resistance genes erm(C), aacA-aphD and tet(K) and the number of non-wild type strains with minimum inhibitory concentration values (MICs) above the epidemiological cut-off values (ECOFFs) for gentamicin and kanamycin. Overall, MRSA with non-wild type phenotype for the macrolide-lincosamide-streptogramin group, tetracycline, and trimethoprim were found in more than 70% of poultry isolates. Non-wild type isolates carrying the qacC gene conferring resistance to quaternary ammonium compound disinfectants were found at all production stages in similar frequencies. Regarding the presence of enterotoxin genes in poultry-derived MRSA the enterotoxin gene cluster (egc) was only found in Non-CC (clonal complex) 398 strains. Three CC398 strains harboured the genes sed (from turkey at slaughter and broiler meat) and sea-N315 (from a chicken carcass). One Non-CC398 strain isolated from turkey meat was found positive for the seb gene and also enterotoxin production. Similarity analysis based on selected resistance and virulence markers revealed a high clonality among Non-CC398 isolates. Isolates of the same clonal complex clustered together according to their common virulence and resistance profiles. Strains of CC9 were grouped in two subclusters due to different resistance genes. Our results underline, that there are other poultry associated clones of MRSA (mainly CC9 and CC5) besides the predominant CC398 which are similar in both poultry species.

Is the Colonisation of Staphylococcus aureus in Pets Associated with Their Close Contact with Owners?

In human beings and animals, staphylococci constitute part of the normal microbial population. Staphylococcus aureus could be classified as an opportunistic pathogen because the bacteria are noted in clinically healthy individuals, but when the immune system becomes compromised, they can also cause a wide range of infections. The objective of this study was to test the hypothesis that cats who are in close contact with their owners are at the greatest risk of being colonised with S. aureus. Two groups of cats were investigated: single, pet (domestic) cats that do not have outdoor access; and a local population of feral cats living in urban areas. The prevalence of S. aureus in domestic cats was 19.17%, while it's prevalence in the feral cat population was only 8.3%; which was statistically significant. Analysis of antibiotic resistance, at the genotypic as well as phenotypic level, showed that S. aureus isolates from pet cats were more likely to harbour antibiotic resistant determinants. The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in households was 10.21%, while in feral cats it was only 1.4%. In conclusion, this study has revealed a correlation between close contact with humans and a higher risk of the cats being colonised with S. aureus and harbouring the antibiotic resistant determinants.

The pathogenicity and host adaptation of livestock-associated MRSA CC398

The presence of methicillin-resistant Staphylococcus aureus (MRSA) CC398 in livestock and their transmission to humans followed by their introduction into hospitals led to a significant burden for the human healthcare system, especially in regions with a high density of livestock breeding. The CC398 lineage made two host changes in its evolutionary history: From humans to pigs and other livestock-associated animals and back to the human host. These adaptation processes are mirrored by changes of the equipment with virulence factors necessary for successful host change. Here, we consider these factors and their special role during human colonization and infection. Host adaptation of S. aureus CC398 is accompanied by genetic changes that are mainly driven by exchanges of mobile genetic elements. So far, it is not clear, which virulence or adhesion factors are important for S. aureus CC398 in host interaction. Among human and animal-derived MRSA CC398 virulence factors, e.g. (entero-) toxins, were rarely found. Overall, this review provides a comprehensive overview on the emerging S. aureus lineage CC398 by summarizing current knowledge from microbiological, molecular and cellular interaction studies in relation to clinical and epidemiological perspectives.

Methicillin-resistant and methicillin-susceptible Staphylococcus aureus in dairy sheep and in-contact humans: An intra-farm study

Staphylococcus aureus is involved in a wide variety of diseases in humans and animals, and it is considered one of the most significant etiological agents of intramammary infection in dairy ruminants, causing both clinical and subclinical infections. In this study, the intra-farm prevalence and circulation of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) were investigated on an Italian dairy sheep farm previously identified as MRSA-positive by testing bulk tank milk (first isolation in 2012). Human samples (nasal swabs, hand skin samples, and oropharyngeal swabs) from 3 persons working in close contact with the animals were also collected, and the genetic characteristics and relatedness of the MRSA isolates from human and animal sources within the farm were investigated. After 2yr from the first isolation, we confirmed the presence of the same multidrug-resistant strain of MRSA sequence type (ST)1, clonal complex (CC)1, spa type t127, staphylococcal cassette chromosome mec (SCCmec) type IVa, showing identical pulsed field gel electrophoresis (PFGE) and resistance profiles at the farm level in bulk tank milk. Methicillin-resistant S. aureus isolates were detected in 2 out of 556 (0.34%) individual milk samples, whereas MSSA isolates were detected in 10 samples (1.8%). The MRSA were further isolated from udder skin samples from the 2 animals that were MRSA-positive in milk and in 2 of the 3 examined farm personnel. All MRSA isolates from both ovine and human samples belonged to ST(CC)1, spa type t127, SCCmec type IVa, with some isolates from animals harboring genes considered markers of human adaptation. In contrast, all MSSA isolates belonged to ruminant-associated CC130, ST700, spa type t528. Analysis by PFGE performed on selected MRSA isolates of human and animal origin identified 2 closely related (96.3% similarity) pulsotypes, displaying only minimal differences in gene profiles (e.g., presence of the immune evasion cluster genes). Although we observed low MRSA intra-farm prevalence, our findings highlight the importance of considering the possible zoonotic potential of CC1 livestock-associated MRSA, in view of the ability to persist over years at the farm level. Biosecurity measures and good hygiene practices could be useful to prevent MRSA spread at the farm level and to minimize exposure in the community and in categories related to farm animal industry (e.g., veterinarians, farmers, and farm workers).

Emerging issues in antimicrobial resistance of bacteria from food-producing animals

During the last decade, antimicrobial resistance in bacteria from food-producing animals has become a major research topic. In this review, different emerging resistance properties related to bacteria of food-producing animals are highlighted. These include: extended-spectrum β-lactamase-producing Enterobacteriaceae; carbapenemase-producing bacteria; bovine respiratory tract pathogens, such as Pasteurella multocida and Mannheimia haemolytica, which harbor the multiresistance mediating integrative and conjugative element ICEPmu1; Gram-positive and Gram-negative bacteria that carry the multiresistance gene cfr; and the occurrence of numerous novel antimicrobial resistance genes in livestock-associated methicillin-resistant Staphylococcus aureus. The emergence of the aforementioned resistance properties is mainly based on the exchange of mobile genetic elements that carry the respective resistance genes.

Health and health-related quality of life in pig farmers carrying livestock-associated methicillin-resistant Staphylococcus aureus

There is limited knowledge about the effect of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) carriage on health-related quality of life (QoL). With this study, we explored whether LA-MRSA causes infections or affects health-related QoL in pig farmers. This prospective cohort study surveyed persons working on 49 farrowing pig farms in The Netherlands for 1 year (2010-2011). On six sampling moments, nasal swabs, environmental samples and questionnaires on activities and infections were collected. At the end of the study year, persons were asked about their QoL using the validated SF-36 and EQ-5D questionnaires. Of 120 persons, 44 (37%) were persistent MRSA carriers. MRSA carriage was not associated with infections, use of antimicrobials, healthcare contact and health-related QoL items in univariate or multivariate analysis, most likely due to the 'healthy worker effect'. Despite high carriage rates, the impact of LA-MRSA carriage in this population of relatively healthy pig farmers on health and health-related QoL appears limited; more research is needed for confirmation.

Worldwide Epidemiology and Antibiotic Resistance of Staphylococcus aureus

Staphylococcus aureus is an important human pathogen, responsible for infections in the community and the healthcare setting. Although much of the attention is focused on the methicillin-resistant "variant" MRSA, the methicillin-susceptible counterpart (MSSA) remains a prime species in infections. The epidemiology of S. aureus, especially of MRSA, showed a rapid evolution in the last years. After representing a typical nosocomial multidrug-resistant pathogen, MRSA has recently emerged in the community and among farmed animals thanks to its ability to evolve and adapt to different settings. Global surveillance has shown that MRSA represents a problem in all continents and countries where studies have been carried out, determining an increase in mortality and the need to use last-resource expensive antibiotics. S. aureus can easily acquire resistance to antibiotics and MRSA is characteristically multidrug resistant. Resistance to vancomycin, the principal anti-MRSA antibiotic is rare, although isolates with decreased susceptibility are recovered in many areas. Resistance to the more recently introduced antibiotics, linezolid and daptomycin, has emerged; however, they remain substantially active against the large majority of MSSA and MRSA. Newer antistaphylococcal drugs have been developed, but since their clinical use has been very limited so far, little is known about the emergence of resistance. Molecular typing techniques have allowed to identify the major successful clones and lineages of MSSA and MRSA, including high-risk clones, and to trace their diffusion. In the face of a continuously evolving scenario, this review depicts the most common clones circulating in different geographical areas and in different settings at present. Since the evolution of S. aureus will continue, it is important to maintain the attention on the epidemiology of S. aureus in the future with a global view.

Epidemiology of Staphylococcus aureus Nasal Carriage Patterns in the Community

Staphylococcus aureus (S. aureus) is a Gram-positive opportunistic pathogen that colonizes frequently and asymptomatically the anterior nares of humans and animals. It can cause different kinds of infections and is considered to be an important nosocomial pathogen. Nasal carriage of S. aureus can be permanent or intermittent and may build the reservoir for autogenous infections and cross-transmission to other individuals. Most of the studies on the epidemiology of S. aureus performed in the past were focused on the emergence and dissemination of methicillin-resistant Staphylococcus aureus (MRSA) in healthcare settings. There are, however, a number of more recent epidemiological studies have aimed at analysing carriage patterns over time in the community settings providing new insights on risk factors for colonization and important data for the development of strategies to prevent infections. This chapter aims to give a review of current epidemiological studies on S. aureus carriage patterns in the general community and put them into perspective with recent, yet unpublished, investigations on the S. aureus epidemiology in the general population in northern Germany.

Understanding Staphylococcal Nomenclature

Bacteria are often grouped by a variety of properties, including biochemical activity, appearance, and more recently, nucleic acid sequence differences. In the case of human pathogens, significant work goes into "typing" strains to understand relatedness. This is especially true when trying to understand the epidemiology of these organisms. In attempts to group Staphylococci, a variety of methods and nomenclatures have been employed, which can often serve as a point of confusion to those entering the field. Therefore, the intent of this chapter is to give a brief overview of some common methods and associated nomenclature used to type Staphylococci, with S. aureus as an example.

Methicillin-resistant Staphylococcus aureus from infections in horses in Germany are frequent colonizers of veterinarians but rare among MRSA from infections in humans

A total of 272 methicillin-resistant Staphylococcus aureus (MRSA) from equine infections originating from 17 equine hospitals and 39 veterinary practices in Germany as well as 67 isolates from personnel working at equine clinics were subjected to molecular typing. The majority of isolates from horses was attributed to clonal complex (CC) 398 (82.7%). Within CC398, 66% of isolates belonged to a subpopulation (clade) of CC398, which is associated with equine clinics.

MRSA attributed to CC8 (ST254, t009, t036, SCCmecIV; ST8, t064, SCCmecIV) were less frequent (16.5%). Single isolates were attributed to ST1, CC22, ST130, and ST1660. The emergence of MRSA CC22 and ST130 in horses was not reported so far. Nasal MRSA colonization was found in 19.5% of veterinary personnel with occupational exposure to horses. The typing characteristics of these isolates corresponded to isolates from equine infections.

Comparing typing characteristics of equine isolates with those of a substantial number of isolates from human infections typed at the German Reference Center for Staphylococci and Enterococci (2006–2014; n = 10864) yielded that the proportion of isolates exhibiting characteristics of MRSA from equine medicine is very low (< 0.5%). As this low proportion was also found among MRSA originating from nasal screenings of human carriers not suffering from a staphylococcal infection (n = 5546) transmission of MRSA from equine clinics to the community seems to be rare so far.

Analysis of Transmission of MRSA and ESBL-E among Pigs and Farm Personnel

Livestock-associated bacteria with resistance to two or more antibiotic drug classes have heightened our awareness for the consequences of antibiotic consumption and spread of resistant bacterial strains in the veterinary field. In this study we assessed the prevalence of concomitant colonization with livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) and enterobacteriaceae expressing extended-spectrum betalactamases (ESBL-E) in farms at the German-Dutch border region. Nasal colonization of pigs with MRSA (113/547 (20.7%)) was less frequent than rectal colonization with ESBL-E (163/540 (30.2%)). On the individual farm level MRSA correlated with ESBL-E recovery. The data further provide information on prevalence at different stages of pig production, including abattoirs, as well as in air samples and humans living and working on the farms. Notably, MRSA was detected in stable air samples of 34 out of 35 pig farms, highlighting air as an important MRSA transmission reservoir. The majority of MRSA isolates, including those from humans, displayed tetracycline resistance and spa types t011 and t034 characteristic for LA-MRSA, demonstrating transmission from pigs to humans. ESBL-E positive air samples were detected on 6 out of 35 farms but no pig-to-human transmission was found. Detection of ESBL-E, e.g. mostly Escherichia coli with CTX-M-type ESBL, was limited to these six farms. Molecular typing revealed transmission of ESBL-E within the pig compartments; however, related strains were also found on unrelated farms. Although our data suggest that acquisition of MRSA and ESBL-E might occur among pigs in the abattoirs, MRSA and ESBL-E were not detected on the carcasses. Altogether, our data define stable air (MRSA), pig compartments (ESBL-E) and abattoir waiting areas (MRSA and ESBL-E) as major hot spots for transmission of MRSA and/or ESBL-E along the pig production chain.

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with low within-herd prevalence of intra-mammary infections in dairy cows: Genotyping of isolates

Staphylococcus aureus is one of the most common mastitis-causing pathogens worldwide. In the last decade, livestock-associated methicillin-resistant S. aureus (LA-MRSA) infections have been described in several species, included the bovines. Hence, this paper investigates the diffusion of MRSA within Italian dairy herds; the strains were further characterized using a DNA microarray, which detects 330 different sequences, including the methicillin-resistance genes mecA and mecC and SCCmec typing. The analysis of overall patterns allows the assignment to Clonal Complexes (CC). Overall 163 S. aureus isolates, collected from quarter milk samples in 61 herds, were tested. MRSA strains were further processed using spa typing. Fifteen strains (9.2%), isolated in 9 herds (14.75%), carried mecA, but none harboured mecC. MRSA detection was significantly associated (P<0.011) with a within-herd prevalence of S. aureus intra-mammary infections (IMI) ≤5%. Ten MRSA strains were assigned to CC398, the remaining ones to CC97 (n=2), CC1 (n=2) or CC8 (n=1). In 3 herds, MRSA and MSSA co-existed: CC97-MRSA with CC398-MSSA, CC1-MRSA with CC8-MSSA and CC398-MRSA with CC126-MSSA. The results of spa typing showed an overall similar profile of the strains belonging to the same CC: t127-CC1, t1730-CC97, t899 in 8 out of 10 CC398. In the remaining 2 isolates a new spa type, t14644, was identified. The single CC8 was a t3092. The SCCmec cassettes were classified as type IV, type V or type IV/V composite. All or most strains harboured the genes encoding the β-lactamase operon and the tetracycline resistance. Streptogramin resistance gene was related to CC398. Enterotoxin and leukocidin genes were carried only by CC1, CC8 and CC97-MRSA. The persistence of MRSA clones characterized by broader host range, in epidemiologically unrelated areas and in dairy herds with low prevalence of S. aureus IMI, might enhance the risk for adaptation to human species.

Preventing introduction of livestock associated MRSA in a pig population--benefits, costs, and knowledge gaps from the Swedish perspective

Antibiotic resistance is a growing concern in human, as well as in veterinary medicine. Part of the problem concerns how to respond to the risk presented by animal reservoirs of resistant bacteria with the potential of spreading to humans. One example is livestock associated methicillin-resistant Staphylococcus aureus (LA-MRSA). In countries where LA-MRSA is endemic in the pig population, people in contact with pigs have a higher risk of being colonised with LA-MRSA, and persons from this group are subjected to precautionary measures when visiting health care facilities. In the present study, it is assumed that, if LA-MRSA was introduced to the Swedish pig population, the prevalence in the risk groups would be the same as in Denmark or the Netherlands (two countries with low human prevalence that have implemented measures to detect, trace and isolate human LA-MRSA cases and, therefore, have comprehensive data with good coverage regarding prevalence of LA-MRSA), and that similar interventions would be taken in Swedish health care facilities. It is also assumed that the Swedish pig population is free of MRSA or that the prevalence is very low. We analyse if it would be efficient for Sweden to prevent its introduction by testing imported live breeding pigs. Given that quarantining and testing at import will prevent introduction to the pig population, the study shows that the preventive measures may indeed generate a societal net benefit. Benefits are estimated to be between € 870 720 and € 1 233 511, and costs to € 211 129. Still, due to gaps in knowledge, the results should be confirmed when more information become available.

What Is the Origin of Livestock-Associated Methicillin-Resistant Staphylococcus aureus Clonal Complex 398 Isolates from Humans without Livestock Contact? An Epidemiological and Genetic Analysis

Fifteen percent of all methicillin-resistant Staphylococcus aureus (MRSA) clonal complex 398 (CC398) human carriers detected in The Netherlands had not been in direct contact with pigs or veal calves. To ensure low MRSA prevalence, it is important to investigate the likely origin of this MRSA of unknown origin (MUO). Recently, it was shown that CC398 strains originating from humans and animals differ in the presence of specific mobile genetic elements (MGEs). We hypothesized that determining these specific MGEs in MUO isolates and comparing them with a set of CC398 isolates of various known origin might provide clues to their origin. MUO CC398 isolates were compared to MRSA CC398 isolates obtained from humans with known risk factors, a MRSA CC398 outbreak isolate, livestock associated (LA) MRSA CC398 isolates from pigs, horses, chickens, and veal calves, and five methicillin-susceptible Staphylococcus aureus (MSSA) CC398 isolates of known human origin. All strains were spa typed, and the presence or absence of, scn, chp, φ3 int, φ6 int, φ7 int, rep7, rep27, and cadDX was determined by PCRs. The MRSA CC398 in humans, MUO, or MRSA of known origin (MKO) resembled MRSA CC398 as found in pigs and not MSSA CC398 as found in humans. The distinct human MSSA CC398 spa type, t571, was not present among our MRSA CC398 strains; MRSA CC398 was tetracycline resistant and carried no φ3 bacteriophage with scn and chp. We showed by simple PCR means that human MUO CC398 carriers carried MRSA from livestock origin, suggestive of indirect transmission. Although the exact transmission route remains unknown, direct human-to-human transmission remains a possibility as well.

Prevalence of the immune evasion gene cluster in Staphylococcus aureus CC398

The immune evasion gene cluster (IEC) is typical for Staphylococcus aureus isolated from humans but is usually absent in S. aureus isolated from animals. Previous studies have shown that methicillin resistant S. aureus (MRSA) CC398 obviously lost the IEC when evolving as livestock-associated MRSA from a human-adapted, methicillin-susceptible ancestor. This study aimed to look for the presence of IEC in MRSA from pigs and horses as well as from the colonization of humans with occupational animal contact and from infections in humans. For comparison, methicillin susceptible S. aureus (MSSA) isolates from infections in humans were included. We did not detect the IEC among 94 isolates from the nasal colonization of pigs; however, the IEC was found in 6 of 61 isolates from nosocomial infections in horses. MRSA CC398 isolates from the nasal colonization of 138 pig farmers were negative for the IEC. It was detected, however, in 4 of 69 veterinarians treating horses. Among 99 epidemiologically unrelated MRSA isolates attributed to CC398 originating from infections in humans, 19 were positive for the IEC. Only three of these isolates which also contained luk-PV were attributed to the ancestral, human-adapted subpopulation of CC398 by means of PCR for detection of canonical SNPs. A considerable proportion of LA-MRSA CC398 attributed to the animal subpopulation and originating from infections in humans had acquired the IEC; this acquisition is, however, obviously not a prerequisite to the capacity of LA-MRSA CC398 to cause infections in this host. Among 15 MSSA CC398 isolates from infections in humans, 11 contained the IEC, and of these, two were attributed to the animal subpopulation. Six isolates containing both the IEC and luk-PV were attributed to the ancestral, human subpopulation. Re-acquisition of the IEC by LA-MRSA CC398 suggests readaptation to the human host. In epidemiological surveillance, discrimination from the ancestral human subpopulation is important.

Staphylococcus aureus complex from animals and humans in three remote African regions

Staphylococcus schweitzeri has been recently considered to be a highly divergent Staphylococcus aureus clade and usually colonises nonhuman primates and bats in sub-Saharan Africa. Its transmissibility to humans remains unclear. We therefore investigated the transmission of S. aureus and S. schweitzeri among humans, domestic animals, and wildlife in three remote African regions. A cross-sectional study on nasal and pharyngeal colonisation in humans (n = 1288) and animals (n = 698) was performed in Côte d'Ivoire, Gabon, and Democratic Republic of Congo (DR Congo). Isolates were subjected to spa typing and multilocus sequence typing. Antimicrobial susceptibility and selected virulence factors were tested. S. schweitzeri was found in monkeys from all study sites but no transmission to humans was evident, despite frequent contact of humans with wildlife. In contrast, human-associated S. aureus sequence types (ST1, ST6, ST15) were detected in domestic animals and nonhuman primates, pointing toward a human-to-monkey transmission in the wild. The proportion of methicillin-resistant S. aureus (MRSA) among all S. aureus was 0% (Gabon), 1.7% (DR Congo), and 5.3% (Côte d'Ivoire). The majority of MRSA isolates belonged to the African clone ST88. In conclusion, we did not find any evidence for a transmission of S. schweitzeri from animals to humans. However, such a transmission might remain possible due to the close phylogenetic relation of humans and nonhuman primates. The ST88-MRSA clone was widespread in Côte d'Ivoire but not in Gabon and DR Congo.

Genetic diversity of livestock-associated MRSA isolates obtained from piglets from farrowing until slaughter age on four farrow-to-finish farms

During a previous longitudinal study, performed on four farrow-to-finish farms (A to D), samples were taken from twelve sows, their offspring, and the environment on various occasions over six months to study the MRSA presence. During the present study, a selection of the obtained MRSA isolates were typed by multiple-locus variable-number tandem-repeat analysis (MLVA), Pulsed Field Gel Electrophoresis (PFGE), spa typing, and SCCmec typing to study the genetic diversity of LA-MRSA isolates and to determine possible MRSA sources for pig(let)s. PFGE, spa typing, and SCCmec typing revealed the presence of one or few dominant genotype(s) per farm. In contrast, 212 MLVA types were detected on the four farms, forming one cluster on farm A, three on farm B, four on farm C and two on farm D. The genotype, found on farm A was unique for this farm. Farms B, C and D shared one cluster. In general, MLVA types from these clusters were isolated from piglets, sows, and the environment on various sampling events. Piglets carried MLVA types both related and unrelated to their mother sows’ MLVA types at farrowing and onwards. In conclusion, molecular typing revealed that within a farm one or a few dominant strain(s) are widespread. Potential MRSA sources for piglets were mother sows, the environment and other piglets.

Risk factors for MRSA in fattening pig herds - a meta-analysis using pooled data

The importance of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) as an infectious agent for humans has increased in recent years in Germany. Although it is well known that the prevalence of MRSA in pig farms is high, risk factors for the presence of MRSA in herds of fattening pigs are still poorly understood. The aim of this study was to evaluate available data from previous studies on MRSA in fattening pigs in a meta-analysis to answer the question: What are the factors associated with the occurrence of MRSA in fattening pig herds? The studies on MRSA in pigs that were identified by literature research were heterogeneous with respect to the risk factors investigated and the type of herds focused on. Therefore we decided to carry out a pooling analysis on herd level rather than a typical meta-analysis. Eligible herd data were identified based on the published literature and communication with the authors. The final data set covered 400 fattening pig herds from 10 different studies and 12 risk factors. The prevalence of MRSA in the 400 fattening pig herds was 53.5%. Data were analyzed using generalized estimating equations (GEE). The resulting multivariate model confirmed previously identified risk factors for MRSA in pig herds (herd size and herd type). It also identified further risk factors: group treatment of fattening pigs with antimicrobial drugs (OR=1.79) and housing fattening pig herds on at least partially slatted floors (OR=2.39) compared to plain floor. In contrast, according to the model, fattening pig herds on farms keeping other livestock along with pigs were less likely to harbor MRSA (OR=0.54). The results underline the benefits from a pooling analysis and cooperative re-evaluation of published data.

Occurrence of methicillin-resistant Staphylococcus aureus in farm workers and the livestock environment in Mecklenburg-Western Pomerania, Germany

Background

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has a wide host range and is transmissible to humans, especially to those with close contact to colonized animals. This study presents the first data on the occurrence of MRSA in farm workers and livestock farms (pig, cattle and poultry) in the federal state of Mecklenburg-Western Pomerania in northeast Germany. 78 farm workers at pig farms, cattle farms and poultry farms were tested for MRSA via pooled nasal and pharyngeal swabs. Additionally, from each of the 34 participating farms (17 pig farms, 11 cattle farms, 6 poultry farms) five dust samples were taken from the direct surroundings of the animals. Furthermore, oropharyngeal swabs were additionally taken from 10 animals per poultry farm. Isolated MRSA strains were characterized and confirmed using PCR and spa typing. Resistance patterns were obtained using the broth microdilution assay.

Results

In total, 20 of 78 (25.6%; 95% CI:17.3-36.3) farm workers were positive for MRSA. All MRSA-positive workers were employed at pig farms. Six of 17 (35.3%; 95% CI:17.3-58.7) pooled dust samples from pig farms were also positive. Overall, six spa types were identified, of which t034 predominated. All strains belonged to LA-MRSA CC398 and were resistant to tetracycline. Resistance to lincosamides, macrolides, fluoroquinolones and aminoglycosides was present in some strains. Three farm workers harbored the identical spa type and antimicrobial resistance pattern found in the corresponding dust sample. Neither workers, dust samples from cattle and poultry farms, nor oropharyngeal poultry swabs tested positive for MRSA.

Conclusions

The present study emphasizes the importance of MRSA on pig farms and pig-farm workers in the rural region of Mecklenburg-Western Pomerania, whereas LA-MRSA could not be isolated from cattle and poultry farms.

First description of PVL-positive methicillin-resistant Staphylococcus aureus (MRSA) in wild boar meat

Staphylococcus aureus is an important food-borne pathogen due to the ability of enterotoxigenic strains to produce staphylococcal enterotoxins (SEs) in food. Methicillin-resistant S. aureus (MRSA) is also an important pathogen for humans, causing severe and hard to treat diseases in hospitals and in the community due to its multiresistance against antimicrobials. In particular, strains harbouring genes encoding for the Panton-Valentine leukocidin (PVL) toxin are of concern from a public health perspective as they are usually capable of causing severe skin and soft tissue infections (sSSTIs) and occasionally necrotizing pneumonia which is associated with high mortality. This is the first report on the detection of MRSA with genes encoding for PVL in wild boar meat. Among the 28 MRSA isolated from wild boar meat in the course of a national monitoring programme in Germany, seven harboured PVL-encoding genes. Six of the isolates were identical according to the results of spa-, MLST-, microarray- and PFGE-typing. They could be assigned to the epidemic MRSA clone USA300. Epidemiological investigations revealed that people handling the food were the most likely common source of contamination with these MRSA. These findings call again for suitable hygienic measures at all processing steps of the food production chain. The results of the study underline that monitoring along the food chain is essential to closely characterise the total burden of MRSA for public health.

LA-MRSA CC398 differ from classical community acquired-MRSA and hospital acquired-MRSA lineages: functional analysis of infection and colonization processes

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) of the clonal complex (CC) 398 became primarily known as colonizers of livestock animals. In the past few years, they have been increasingly introduced into hospitals with subsequent emergence of human infections. However, the (re-)adaptation to the human host is only incompletely understood. This study aimed to assess virulence properties of LA-MRSA CC398 by functional modeling of infection and colonization processes. A selection of 15 human LA-MRSA CC398 isolates and 11 pig-colonizing isolates were characterized regarding their virulence capacities and compared with human isolates of hospital-acquired (HA)-MRSA (CC5, CC22 and CC45) and community-associated (CA)-MRSA (CC8, CC30 and CC80) clonal lineages. Our investigations demonstrated that LA-MRSA CC398 adhered less efficient to human cells and human/bovine plasma fibronectin than CA-MRSA and HA-MRSA isolates. In contrast, the LA-MRSA CC398 isolates revealed a high cytotoxic potential comparable to certain CA-MRSA. Comparing the most prevalent LA-MRSA CC398 spa types (t011, t034, t108), isolates associated with spa t108 showed an increased adhesive and invasive potential paired with an increased ability to evade phagocytosis. The results underline both the pathogenic potential of LA-MRSA in general and the heterogeneity within the CC398 clade regarding the virulence characteristics of CC398 subpopulations. Assuming an ongoing (re-)adaptation to the human host combined with a huge reservoir of LA-MRSA CC398 in livestock and constant zoonotic transmission, the LA-MRSA CC398 lineage has the potential to pose a serious threat to human health.

Methicillin susceptible Staphylococcus aureus (MSSA) of clonal complex CC398, t571 from infections in humans are still rare in Germany

Methicillin-susceptible Staphylococcus aureus (MSSA) attributed to clonal complex (CC) 398 and exhibiting spa-type t571 received attention in Europe and in the USA for being associated with severe infections in humans. As this spa-type is exhibited by livestock-associated (LA) Methicillin-resistant S. aureus (MRSA) as well, it is important to discriminate LA- and human-derived strains by easy to perform, PCR-based methods. MSSA t571 contain phage int3 carrying scn and chp, whereas LA-MRSA t571 lack these markers. In contrast, pathogenicity island SaPIbov5 (detected by PCR bridging vwbbov and scn) is contained by LA-MRSA t571 and absent in the human MSSA subpopulation. Furthermore, MSSA t571 contain erm(T), the particular genomic arrangement of which was assessed by a PCR bridging erm(T) and the adjacent transposase gene. MSSA t571 are rare so far in Germany among isolates from infections in humans (0.14%) as well as among isolates from nasal colonization (0.13%). LA-MRSA t571 are also infrequent among MRSA isolated from carriage at admission to hospitals (0.1%) and also among isolates from infections in humans (0.013%).