Methicillin-resistant Staphylococcus Aureus CC398 Research Articles

Detection of a cfr-positive MRSA CC398 strain in a pig farmer in Spain

ObjectiveTo characterize one linezolid- and methicillin-resistant Staphylococcus aureus (MRSA) isolate recovered from a nasal sample of a pig farmer patient. MethodsThe detection of linezolid resistance mechanisms was performed by PCR and sequencing. The antimicrobial resistance and virulence profile was investigated, and the molecular typing was performed by molecular techniques. The transference of cfr gene was assessed by conjugation experiments and its genetic environment was investigated by specific PCRs. ResultsThe linezolid-resistant MRSA isolate was typed as t011-ST398/CC398-SCCmecV-agrI and carried the cfr gene. The isolate was multidrug-resistant but lacked the virulence genes studied. The cfr gene was co-located with the fexA gene on a Tn558 variant and was successfully transferred by conjugation. ConclusionWe report the first description of LA-MRSA-CC398 carrying the cfr gene in Spain. This finding highlights the importance of surveillance programmes to determine the presence and spread of the cfr gene in the livestock and clinical settings.

Genotyping of methicillin resistant Staphylococcus aureus from the United Arab Emirates

Reports from Arabian Gulf countries have demonstrated emergence of novel methicillin resistant Staphylococcus aureus (MRSA) strains. To address the lack of data from the United Arab Emirates (UAE), genetic characterisation of MRSA identified between December 2017 and August 2019 was conducted using DNA microarray-based assays. The 625 MRSA isolates studied were grouped into 23 clonal complexes (CCs) and assigned to 103 strains. CC5, CC6, CC22 and CC30 represented 54.2% (n/N = 339/625) of isolates with other common CCs being CC1, CC8, CC772, CC361, CC80, CC88. Emergence of CC398 MRSA, CC5-MRSA-IV Sri Lanka Clone and ST5/ST225-MRSA-II, Rhine-Hesse EMRSA/New York-Japan Clone in our setting was detected. Variants of pandemic CC8-MRSA-[IVa + ACME I] (PVL+) USA300 were detected and majority of CC772 strains were CC772-MRSA-V (PVL+), “Bengal- Bay Clone”. Novel MRSA strains identified include CC5-MRSA-V (edinA+), CC5-MRSA-[VT + fusC], CC5-MRSA-IVa (tst1+), CC5-MRSA-[V/VT + cas + fusC + ccrA/B-1], CC8-MRSA-V/VT, CC22-MRSA-[IV + fusC + ccrAA/(C)], CC45-MRSA-[IV + fusC + tir], CC80-MRSA-IVa, CC121-MRSA-V/VT, CC152-MRSA-[V + fusC] (PVL+). Although several strains harboured SCC-borne fusidic acid resistance (fusC) (n = 181), erythromycin/clindamycin resistance (ermC) (n = 132) and gentamicin resistance (aacA-aphD) (n = 179) genes, none harboured vancomycin resistance genes while mupirocin resistance gene mupR (n = 2) and cfr gene (n = 1) were rare. An extensive MRSA repertoire including CCs previously unreported in the region and novel strains which probably arose locally suggest an evolving MRSA landscape.

Detection of a cfr-positive MRSA CC398 strain in a pig farmer in Spain

ObjectiveTo characterize one linezolid- and methicillin-resistant Staphylococcus aureus (MRSA) isolate recovered from a nasal sample of a pig farmer patient. MethodsThe detection of linezolid resistance mechanisms was performed by PCR and sequencing. The antimicrobial resistance and virulence profile was investigated, and the molecular typing was performed by molecular techniques. The transference of cfr gene was assessed by conjugation experiments and its genetic environment was investigated by specific PCRs. ResultsThe linezolid-resistant MRSA isolate was typed as t011-ST398/CC398-SCCmecV-agrI and carried the cfr gene. The isolate was multidrug-resistant but lacked the virulence genes studied. The cfr gene was co-located with the fexA gene on a Tn558 variant and was successfully transferred by conjugation. ConclusionWe report the first description of LA-MRSA-CC398 carrying the cfr gene in Spain. This finding highlights the importance of surveillance programmes to determine the presence and spread of the cfr gene in the livestock and clinical settings.

Methicillin-resistant Staphylococcus aureus alters cell wall glycosylation to evade immunity.

Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent cause of difficult-to-treat, often fatal infections in humans1,2. Most humans have antibodies against S. aureus, but these are highly variable and often not protective in immunocompromised patients3. Previous vaccine development programs have not been successful4. A large percentage of human antibodies against S. aureus target wall teichoic acid (WTA), a ribitol-phosphate (RboP) surface polymer modified with N-acetylglucosamine (GlcNAc)5,6. It is currently unknown whether the immune evasion capacities of MRSA are due to variation of dominant surface epitopes such as those associated with WTA. Here we show that a considerable proportion of the prominent healthcare-associated and livestock-associated MRSA clones CC5 and CC398, respectively, contain prophages that encode an alternative WTA glycosyltransferase. This enzyme, TarP, transfers GlcNAc to a different hydroxyl group of the WTA RboP than the standard enzyme TarS7, with important consequences for immune recognition. TarP-glycosylated WTA elicits 7.5-40-fold lower levels of immunoglobulin G in mice than TarS-modified WTA. Consistent with this, human sera contained only low levels of antibodies against TarP-modified WTA. Notably, mice immunized with TarS-modified WTA were not protected against infection with tarP-expressing MRSA, indicating that TarP is crucial for the capacity of S. aureus to evade host defences. High-resolution structural analyses of TarP bound to WTA components and uridine diphosphateGlcNAc (UDP-GlcNAc) explain the mechanism of altered RboP glycosylation and form a template for targeted inhibition of TarP. Our study reveals an immune evasion strategy of S. aureus based on averting the immunogenicity of its dominant glycoantigen WTA. These results will help with the identification of invariant S. aureus vaccine antigens and may enable the development of TarP inhibitors as a new strategy for rendering MRSA susceptible to human host defences.

Variability of SCCmec elements in livestock-associated CC398 MRSA

The most common livestock-associated lineage of methicillin-resistant Staphylococcus aureus (MRSA) in Western Europe is currently clonal complex (CC) 398. CC398-MRSA spread extensively across livestock populations in several Western European countries, and livestock-derived CC398-MRSA strains can also be detected in humans. Based on their SCCmec elements, different CC398 strains can be distinguished. SCCmec elements of 100 veterinary and human CC398-MRSA isolates from Germany and Austria were examined using DNA microarray-based assays. In addition, 589 published SCC and/or genome sequences of CC398-MRSA (including both, fully finished and partially assembled sequences) were analysed by mapping them to the probe sequences of the microarrays. Several isolates and sequences showed an insertion of a large fragment of CC9 genomic DNA into the CC398 chromosome. Fifteen subtypes of SCCmec elements were detected among the 100 CC398 isolates and 41 subtypes could be discerned among the published CC398 sequences. Eleven of these were also experimentally detected within our strain collection, while four subtypes identified in the isolates where not found among the sequences. A high prevalence of heavy metal resistance genes, especially of czrC, was observed among CC398-MRSA. A possible co-selection of resistances to antibiotics and zinc/copper supplements in animal feed as well as a spill-over of SCCmec elements that have evolved in CC398-MRSA to other, possibly more virulent and/or medically relevant S. aureus lineages might pose public health problems in future.

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

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

Characterization of Livestock-Associated Methicillin-Resistant Staphylococcus aureus CC398 and mecC-positive CC130 from Zoo Animals in the United Kingdom.

Little is known about the characteristics and diseases associated with methicillin-resistant Staphylococcus aureus (MRSA) in nondomestic animals. Four presumptive MRSA isolates, obtained from clinical (n = 3) and surveillance specimens (n = 1) from dwarf (Helogale parvula) and yellow mongooses (Cynictis penicillata) from a United Kingdom zoo, were analyzed by PCR for detection of mecA and mecC-mediated methicillin resistance, and virulence genes. Isolates were genotyped by multilocus sequence typing (MLST) and staphylococcal cassette chromosome mec (SCCmec) and spa sequence typing. Three isolates, obtained from the dwarf mongooses, carried mecA, tetK, and fexA resistance and virulence genes (icaA, icaD, and sec) and were typed to SCCmec IVa, spa type t899, and clonal complex (CC) 398. The fourth MRSA isolate, obtained from the femoral bone marrow of a yellow mongoose showing postmortem findings consistent with septicemia, carried mecC and was oxacillin/cefoxitin susceptible, when tested at 37°C but showed a characteristic MRSA susceptibility profile at 25°C ± 2°C. Furthermore, this isolate exhibited a different genetic background (SCCmecXI/t843/CC130) and had biofilm-associated genes (bap, icaA, and icaD) and tetK tetracycline resistance genes. This work describes the first isolation of livestock-associated MRSA CC398 from two zoo mongoose species where it was associated with both clinical disease and colonization, and the first isolation of mecC MRSA from a zoo species in the United Kingdom. Both reports highlight the potential for zoo species to act as reservoirs for these zoonotic agents.

Environmental surveillance identifies multiple introductions of MRSA CC398 in an Equine Veterinary Hospital in the UK, 2011\u20132016

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

Horses in Denmark Are a Reservoir of Diverse Clones of Methicillin-Resistant and -Susceptible Staphylococcus aureus.

Denmark is a country with high prevalence of livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) clonal complex (CC) 398 in pigs. Even though pig farming is regarded as the main source of human infection or colonization with MRSA CC398, 10–15% of the human cases appear not to be linked to pigs. Following the recent reports of MRSA CC398 in horses in other European countries and the lack of knowledge on S. aureus carriage in this animal species, we carried out a study to investigate whether horses constitute a reservoir of MRSA CC398 in Denmark, and to gain knowledge on the frequency and genetic diversity of S. aureus in horses, including both methicillin-resistant and -susceptible S. aureus (MSSA). Nasal swabs were collected from 401 horses originating from 74 farms, either at their farms or prior to admission to veterinary clinics. Following culture on selective media, species identification by MALDI-TOF MS and MRSA confirmation by standard PCR-based methods, S. aureus and MRSA were detected in 54 (13%) and 17 (4%) horses originating from 30 (40%) and 7 (9%) farms, respectively. Based on spa typing, MSSA differed genetically from MRSA isolates. The spa type prevalent among MSSA isolates was t127 (CC1), which was detected in 12 horses from 11 farms and represents the most common S. aureus clone isolated from human bacteremia cases in Denmark. Among the 17 MRSA carriers, 10 horses from three farms carried CC398 t011 harboring the immune evasion cluster (IEC), four horses from two farms carried IEC-negative CC398 t034, and three horses from two farms carried a mecC-positive MRSA lineage previously associated with wildlife and domestic ruminants (CC130 t528). Based on whole-genome phylogenetic analysis of the 14 MRSA CC398, t011 isolates belonged to the recently identified horse-adapted clone in Europe and were closely related to human t011 isolates from three Danish equine veterinarians, whereas t034 isolates belonged to pig-adapted clones. Our study confirms that horses carry an equine-specific clone of MRSA CC398 that can be transmitted to veterinary personnel, and reveals that these animals are exposed to MRSA and MSSA clones that are likely to originate from livestock and humans, respectively.

Clinical impact and prevalence of MRSA CC398 and differences between MRSA-TetR and MRSA-TetS in an area of Spain with a high density of pig farming: a prospective cohort study

ObjectivesTetracycline resistance (TetR) is a phenotypic marker of the livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) CC398 clone. The aim of this study was to analyse the prevalence of MRSA CC398 in patients in contact with healthcare facilities and differences between patients with MRSA-TetR and MRSA tetracycline-susceptible (TetS) strains. MethodsPatients diagnosed with MRSA from January 2012 to December 2015 were divided into two groups, MRSA-TetR and MRSA-TetS. Epidemiologic and clinical data were evaluated. Molecular analysis was performed (multilocus sequence typing, spa typing) on MRSA-TetR strains. ResultsData from 288 MRSA patients were obtained, and 106 (36.8%) carried MRSA-TetR (93 typed as CC398 (87.7%); the remaining 13 isolates were ascribed to CC9, CC1, CC121, CC30, CC97, CC146 and CC152). The most frequent spa type was t011 (56.6%, 61/106). Detection of MRSA-TetR increased over the years (21.9%, 16/73, in 2012; 50.7%, 36/71, in 2015; p <0.001). Hospital acquisition was found in 16.7% (19/114) of MRSA-TetR patients vs. 83.3% (95/114) in MRSA-TetS patients (p <0.001). Frequency of MRSA-TetR patients in nursing homes was lower than in MRSA-TetS patients (4.7%, 5/106, vs. 27.5%, 50/182, p <0.001). MRSA-TetR as distinct from MRSA-TetS was associated with workers on pig farms (49.0%, 52/106, vs. 1.0%, 2/182; p <0.001), fewer admissions to hospital (46.2%, 49/106, vs. 68.1%, 124/182; p <0.001) and fewer comorbidities (81.1%, 86/106, vs. 59.9%, 109/182; p <0.001). Sixty cases of MRSA-CC398 infection were diagnosed, including, among others, endocarditis, septic arthritis, prosthetic joint infection, pneumonia and bacteraemia. ConclusionsPrevalence of MRSA-TetR (especially CC398) at the hospital level in a Spanish region with intensive pig farming activity is high and is responsible for severe infections. Significant differences were detected in clinical and epidemiologic characteristics among MRSA-TetR and MRSA-TetS patients.

Livestock-associated strains of methicillin resistant Staphylococcus aureus (LA-MRSA) – the current state of knowledge

A methicillin-resistant Staphylococcus aureus (MRSA) referred to as livestock-associated (LA-MRSA) has recently emerged in farm animals, particularly in pigs. Strains of this MRSA variant from Europe and North America mostly belong to clonal complex (CC) 398. Generally LA-MRSA cause asymptomatic colonization among pigs, but also in veal calves, broiler chickens, turkeys, and horses. People in contact with livestock animals are at high risk of asymptomatic colonization or infection with these bacteria. In previous years, the impact of LA-MRSA on human health was considered small. However, LA-MRSA has become more prevalent among people without direct livestock contact, especially in areas with a high density of pig production. As a result of horizontal gene transfer S. aureus CC398 strains are constantly evolving. The adaptive power of S. aureus to new hosts and acquisition of resistance to antibiotics may cause the emergence of new, more virulent clones. LA-MRSA has evolved from human-adapted methicillin-susceptible S. aureus CC398, which was proved by comparative genome analysis. The adaptation to livestock was associated with several genetic changes. The most worrying aspect of MRSA CC398 seems to be its ability to spread to humans. For this reason, continuous surveillance of further genetic changes is recommended.

Methicillin-Resistant Staphylococcus aureus CC398 in Humans and Pigs in Norway: A "One Health" Perspective on Introduction and Transmission.

Emerging livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) persist in livestock populations and represent a reservoir for transmission to humans. Understanding the routes of introduction and further transmission is crucial to control this threat to human health. All reported cases of livestock-associated MRSA (CC398) in humans and pigs in Norway between 2008 and 2014 were included. Data were collected during an extensive outbreak investigation, including contact tracing and stringent surveillance. Whole-genome sequencing of isolates from all human cases and pig farms was performed to support and expand the epidemiological findings. The national strategy furthermore included a "search-and-destroy" policy at the pig farm level. Three outbreak clusters were identified, including 26 pig farms, 2 slaughterhouses, and 36 humans. Primary introductions likely occurred by human transmission to 3 sow farms with secondary transmission to other pig farms, mainly through animal trade and to a lesser extent via humans or livestock trucks. All MRSA CC398 isolated from humans without an epidemiological link to the outbreaks were genetically distinct from isolates within the outbreak clusters indicating limited dissemination to the general population. This study identified preventable routes of MRSA CC398 introduction and transmission: human occupational exposure, trade of pigs and livestock transport vehicles. These findings are essential for keeping pig populations MRSA free and, from a "One Health" perspective, preventing pig farms from becoming reservoirs for MRSA transmission to humans.

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.

Persistence of nasal colonisation with methicillin resistant Staphylococcus aureus CC398 among participants of veterinary conferences and occurrence among their household members: A prospective cohort study, Germany 2008–2014

There are only few data on the persistence and transmission of methicillin resistant Staphylococcus aureus (MRSA) of the clonal complex (CC) 398 among veterinarians and their household members. We therefore investigated the long-term colonisation with MRSA CC398 among participants of veterinary conferences in Germany in 2008/2009 and their household members. Forty-five initially MRSA CC398 positive and 180 initially MRSA CC398 negative conference participants were included in a longitudinal study. These persons and their household members were tested for nasal colonisation in 2011, 2012 and 2014. Of 31 continuously tested and initially MRSA CC398 positive participants only 8 (26%) were colonized with MRSA CC398at all 4 time points, 4 (13%) of them consistently with the same spa type. Among initially MRSA CC398 negative participants, 13 (7%) were tested MRSA CC398 positive at least once during the follow-up period. Data for household members at least at one time point were available for 185 households. Of these 21 (11%) households had one or more household member who tested positive for MRSA CC398at least once. The odds of household members to be MRSA CC398 positive was 12 times higher (95% confidence interval 4–37) when the conference participant tested MRSA CC398 positive in 2008/2009. This association remained strong when household members working in veterinary medicine or livestock farms were excluded. In summary, these data suggest that colonisation with MRSA CC398 is partially transient and that household members of MRSA CC398 colonized persons are at an increased risk of colonisation with MRSA CC398.

The Emergence and Spread of Multiple Livestock-Associated Clonal Complex 398 Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus Strains among Animals and Humans in the Republic of Ireland, 2010-2014.

Clonal complex (CC) 398 methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) are associated with carriage and infection among animals and humans but only a single case of CC398 MRSA has been reported in the Republic of Ireland (ROI). The present study investigated the molecular epidemiology of CC398 MRSA (n = 22) and MSSA (n = 10) from animals and humans in the ROI from 2010–2014. Isolates underwent antimicrobial susceptibility testing, spa typing, DNA microarray profiling and PCR for CC398-associated resistance genes. All MRSA underwent SCCmec IV or V subtyping. Four distinct CC398-MRSA incidents were identified from (i) a man in a nursing home (spa type t011-SCCmec IVa, immune evasion complex (IEC) negative), (ii) a horse and veterinarian who had recently travelled to Belgium (t011-IVa, IEC positive), (iii) pigs (n = 9) and farm workers (n = 9) on two farms, one which had been restocked with German gilts and the other which was a finisher farm (t034-VT, IEC negative, 3/9 pigs; t011- VT, IEC negative, 6/9 pigs & 9/9 farm workers), and (iv) a child who had worked on a pig farm in the UK (t034-VT, IEC negative). Isolates also carried different combinations of multiple resistance genes including erm(A), erm(B), tet(K), tet(M) & tet(L), fexA, spc, dfrG, dfrK aacA-aphD and aadD further highlighting the presence of multiple CC398-MRSA strains. CC398 MSSA were recovered from pigs (n = 8) and humans (n = 2). CC398 MSSA transmission was identified among pigs but zoonotic transmission was not detected with animal and human isolates exhibiting clade-specific traits. This study highlights the importation and zoonotic spread of CC398 MRSA in the ROI and the spread of CC398 MSSA among pigs. Increased surveillance is warranted to prevent further CC398 MRSA importation and spread in a country that was considered CC398 MRSA free.

Fatal infections caused by methicillin‐resistant Staphylococcus aureus of clonal complex 398: case presentations and molecular epidemiology

Introduction: Methicillin‐resistant Staphylococcus aureus (MRSA) of clonal complex (CC) 398 has emerged in livestock across Europe over the past 10 years. Case presentation: Case 1 was a patient with a history of destructive chronic polyarthritis and immunosuppressive therapy who presented with dyspnoea and pain in the shoulders, back and hips. Microbiological analysis of tissue samples, punctures and blood cultures revealed MRSA. Echocardiography showed mitral valve endocarditis. The patient was treated with daptomycin and fosfomycin. Case 2 was a patient presenting with pneumonia after lung transplantation. Respiratory specimens and perianal swabs revealed MRSA. The patient was treated with teicoplanin and linezolid. The patients did not recover from their infections and died. The isolates belonged to spa types t2576 (case 1) and t011 (case 2), to sequence type 398 within CC398 as determined by multilocus sequence typing and to staphylococcal cassette chromosome mec type 5. An IdentiBAC Microarray revealed the absence of a bacteriophage integrating into the hlb gene indicative of the livestock origin of the isolates. In 2013, 170 of 534 MRSA cases (31.8 %) among inpatients of the University Hospital Münster, Germany, were caused by closely related spa types clustering in one spa‐CC indicative of CC398. Two of 12 MRSA isolates from blood cultures (16.7 %) were caused by isolates associated with MRSA CC398. Conclusion: Livestock‐associated MRSA CC398 is emerging as a cause of human infections. This observation is alarming and should inspire future efforts to control MRSA in livestock, forestall community spread and monitor changes of the occurrence of MRSA CC398 among cases of human infections.

Are cases of Methicillin-resistant Staphylococcus aureus clonal complex (CC) 398 among humans still livestock-associated?

Methicillin-resistant Staphylococcus aureus (MRSA) of clonal complex (CC) 398 are widespread among pigs, cattle and poultry as well as among humans who have contact to these livestock animals. However, there is limited data on livestock-independent dissemination of MRSA CC398 in the general population. MethodsIn this case–control study MRSA isolates derived (between July 2013 and June 2014) from patients of four hospitals located in a livestock-dense region were S. aureus protein A (spa) typed and risk factors for MRSA acquisition were assessed from patients colonized or infected with MRSA CC398 vs. other MRSA molecular types (MRSA non-CC398). ResultsOf 384 patients, 21% were colonized with MRSA CC398. Contact with livestock (Odds Ratio (OR) 46.03) and residence directly on a pig farm (OR 12.82) were associated with MRSA CC398. Of 55 patients with MRSA CC398, 21 (38%) did not report direct livestock contact. Among the latter we identified several risk factors that could have facilitated indirect transmission, such as living on farms (without being farmer), private contact with known MRSA carriers or previous hospitalization. DiscussionThis study suggests that MRSA CC398 is still mostly disseminated via direct contact to livestock. However, a substantial proportion of patients seem to acquire MRSA CC398 via other pathways.

Characterization of tetracycline and methicillin resistant Staphylococcus aureus strains in a Spanish hospital: Is livestock-contact a risk factor in infections caused by MRSA CC398?

Tetracycline-resistance (TetR) has been postulated as a marker of the livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) lineage CC398. Objectives of the study: to determine the spa-types and assigned MLST clonal complexes (CCs) among all 98 MRSA-TetR strains recovered during 2011–2012 (from different patients) in a Spanish Hospital, analyzing the possible correlation with livestock-contact of the patients. All 98 strains were assigned to 9 CCs: CC398 (60.2%), CC1 (19.4%), CC5 (12.2%), and other CCs (8.2%). The 98 patients were classified into three groups: (A) contact with livestock-animals (n=25); (B) no-contact with livestock-animals (n=42); (C) no information about animal contact (n=31). A significant higher percentage of CC398 strains was obtained in group A (76%) than in group B (50%) (p<0.05), being the percentage in group C of 61.3%. Most of MRSA-TetR-CC398 strains presented a multi-resistance phenotype, including erythromycin, clindamycin, and ciprofloxacin, and the most prevalent detected genes were tet(M) and erm(C). Three strains presented the phenotype macrolide-susceptibility/lincosamide-resistance and contained the vga(A) gene. MRSA-CC1 strains showed higher percentages of erythromycin/clindamycin resistance (95%/89%) than MRSA-CC398 strains (58%/63%), and this resistance was usually mediated by erm(C) gene. Most of MRSA-CC5 strains showed resistance to ciprofloxacin, tobramycin/kanamycin and erythromycin. None of the strains presented the genes lukF/lukS-PV, tsst-1, eta, etb or etd. All MRSA-CC398 strains lacked the genes of the immune-evasion-cluster, but MRSA-CC1 strains carried these genes (type E). In conclusion, although MRSA CC398 is detected in a significant higher proportion in patients with livestock-contact; its detection in people without this type of contact also indicates its capacity for human-to-human transmission.

The impact of zoonotic MRSA colonization and infection in Germany.

Methicillin-resistant Staphylococcus aureus (MRSA) causes colonization and infection both in animals and humans. In Germany, cases of MRSA colonization among humans, w+hich affect 0.5-1.5% of the general population and 1.0-2.5% of patients at hospital admission, are still mostly associated with previous healthcare contact and defined epidemic clonal lineages. However, MRSA is also distributed in livestock production in Germany, mostly without causing infections in the animals. These MRSA predominantly belong to the clonal complex (CC) 398, but also to CC9 and CC97. Zoonotic transmission of MRSA CC398 from livestock to humans occurs predominantly in people with occupational livestock contact. Spread of MRSA CC398 to household members of these persons is also frequently observed, but dissemination in the general population is limited so far However, especially in areas with intensive livestock husbandry, about 20-38% of MRSA CC398 cases among humans cannot be epidemiologically linked to direct livestock contact, indicating other transmission pathways. MRSA CC398 currently causes about 2% of all human MRSA infections (wound infections, pneumonia, sepsis) in Germany, but up to 10% in regions characterized by a high density of livestock-farming. The burden of MRSA in companion animals was demonstrated to range between 3.6-9.4% within wound samples obtained from dogs, cats and horses, respectively. In contrast to livestock and horses, MRSA distributed in pet animals are mostly associated with MRSA clonal lineages that are also prevalent in human healthcare facilities. Overall, zoonotic exchange of MRSA between humans and animals has relevant impact on the epidemiology of MRSA in Germany.

Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) in organic pig herds in The Netherlands.

The prevalence of the methicillin-resistant Staphylococcus aureus (MRSA) among conventional pig herds in the Netherlands is high (around 71%). Nevertheless, information about the prevalence of MRSA among organic pig herds is lacking. Here, we report a study on 24 of the 49 organic pig herds in the Netherlands. The prevalence of MRSA positive herds showed to be 21%. The genetic characteristics of the MRSA isolates were similar to MRSA CC398 described in conventional pigs except one exceptional HA-MRSA CC30 found in one herd, which was presumably caused by human to animal transmission. This resulted in a prevalence of MRSA CC398 in the organic herds of 16.7%.