Community-acquired Methicillin-resistant Staphylococcus Aureus Clone Research Articles

Changing careers: Skin pathogen evolves to infect the bloodstream

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) rose to clinical dominance decades ago and predominantly manifested as skin and soft-tissue infections (SSTIs). These clones were distinct from those causing hospital acquired (HA-MRSA) infections. Dyzenhaus etal. describe the evolutionary changes necessary for CA-MRSA clones to cause bloodstream infections (BSIs).

Prevalence and Genetic Characteristics of Methicillin-Resistant Staphylococcus aureus and Coagulase-Negative Staphylococci Isolated from Oral Cavity of Healthy Children in Japan.

Prevalence and genetic characteristics of methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci in oral cavity of healthy children were studied in Hokkaido, northern main island of Japan. From saliva of 526 children, a total of 248 staphylococcal isolates comprising S. aureus (n = 143), S. epidermidis (n = 84), S. warneri (n = 13), S. haemolyticus (n = 5), S. hominis (n = 2), and S. intermedius (n = 1) were recovered. Presence of mecA was confirmed in 6.3% of S. aureus, 50% of S. epidermidis, and 7.7% in S. warneri. SCCmec was mostly classified into type IV, and ACME (arginine catabolic mobile element)-arcA was detected in S. epidermidis (23.8%) and S. intermedius. Nine MRSA isolates belonged to staphylocoagulase gene (coa) type Ia, IIa, IIIa, VIIb/sequence type 1 (ST1), ST5, ST8, ST89, ST120, and were negative for PVL (Panton-Valentine leukocidin) genes. These isolates included two clones of emerging community-acquired MRSA (CA-MRSA) that had been described recently in Japan: ST5/SCCmec IVc, which resembles the "Pediatric clone," and ST8/SCCmec IVl belonging to coa-IIIa/agr-I with sasL gene, designated "CA-MRSA/J" clone. Various enterotoxin genes were found in all the MRSA and some methicillin-susceptible S. aureus (MSSA) isolates examined, while tst-1 was detected in four MRSA isolates. Notably, a variant of elastin-binding protein gene (ebpS-v) was identified in ST120 MRSA and ST45 MSSA isolates, and exfoliative toxin D gene (etd) was detected in an MSSA isolate. The present study revealed the presence of MRSA, including the novel CA-MRSA clones, and high prevalence of methicillin-resistant S. epidermidis in oral cavity of healthy children in Japan.

Sequential evolution of virulence and resistance during clonal spread of community-acquired methicillin-resistant Staphylococcus aureus

The past two decades have witnessed an alarming expansion of staphylococcal disease caused by community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). The factors underlying the epidemic expansion of CA-MRSA lineages such as USA300, the predominant CA-MRSA clone in the United States, are largely unknown. Previously described virulence and antimicrobial resistance genes that promote the dissemination of CA-MRSA are carried by mobile genetic elements, including phages and plasmids. Here, we used high-resolution genomics and experimental infections to characterize the evolution of a USA300 variant plaguing a patient population at increased risk of infection to understand the mechanisms underlying the emergence of genetic elements that facilitate clonal spread of the pathogen. Genetic analyses provided conclusive evidence that fitness (manifest as emergence of a dominant clone) changed coincidently with the stepwise emergence of (i) a unique prophage and mutation of the regulator of the pyrimidine nucleotide biosynthetic operon that promoted abscess formation and colonization, respectively, thereby priming the clone for success; and (ii) a unique plasmid that conferred resistance to two topical microbiocides, mupirocin and chlorhexidine, frequently used for decolonization and infection prevention. The resistance plasmid evolved through successive incorporation of DNA elements from non-S. aureus spp. into an indigenous cryptic plasmid, suggesting a mechanism for interspecies genetic exchange that promotes antimicrobial resistance. Collectively, the data suggest that clonal spread in a vulnerable population resulted from extensive clinical intervention and intense selection pressure toward a pathogen lifestyle that involved the evolution of consequential mutations and mobile genetic elements.

Dissemination of Panton-Valentine leukocidin–positive methicillin-resistant Staphylococcus aureus USA300 clone in multiple hospitals in Tokyo, Japan

ObjectivesPanton-Valentine leukocidin (PVL) gene (lukS/F-PV)-positive community-acquired methicillin-resistant Staphylococcus aureus (MRSA), particularly the USA300 clone, is a health concern worldwide. Recently, community-acquired MRSA clones have been found to spread and persist in hospital settings. We aimed to investigate the prevalence and molecular epidemiologic features of lukS/F-PV–positive MRSA in Japanese hospitals. MethodsA total of 3433 MRSA isolated from nine hospitals in 2011–2015 were assessed. Molecular epidemiologic analysis performed by staphylococcal cassette chromosome mec typing, PVL typing, arginine catabolic mobile element typing, detection of virulence determinants, multilocus sequence typing, pulsed-field gel electrophoresis and antimicrobial susceptibility testing. ResultsThe detection rate of lukS/F-PV was increased annually from 0.6% (5/817) in 2011 to 3.1% (17/544) in 2015. Molecular epidemiologic analysis for 64 lukS/F-PV–positive MRSA isolates revealed that 42 isolates (65.6%) were the USA300 clone. Resistance rates of levofloxacin and gentamicin among lukS/F-PV–positive isolates increased annually as a result of increased prevalence of the multidrug-resistant USA300 clone. ConclusionsThis is the first report on dissemination of the USA300 clone and PVL-positive MRSA in multiple Japanese hospitals. Our data strongly suggest that the USA300 clone may become epidemic in Japanese hospitals.

Molecular epidemiology of the community-associated methicillin-resistant staphylococcus aureus clones: a synthetic review.

The article presents a synthetic molecular characterization of the methicillin-resistant Staphylococcus aureus and describes the most important community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clones that circulate nowadays in the world: the main molecular and epidemiological characteristics, as well as notions related to the clinic of infections produced by these clones and their antibiotic resistance spectrum.The predominant clone of CA-MRSA in North America is USA300 – ST8-IV in North America, in Australia – Queensland (Qld) MRSA (ST93-IV), in Europe – ST80-IV, in Asia there is a high heterogeneity of clones population, in Africa the distribution of CA-MRSA clones is unclear, and in South America – USA 1100 and USA300-Latin American variant are predominant.The molecular diagnosis is performed by highly specialized institutions. The knowledge of clones allows the study of antibiotic resistance spectrum for each one, a fact of great importance for medical practice. Molecular epidemiology of the CA-MRSA shows that lowly restricted sales of antibiotics in shops and pharmacies, as well as medical prescribing practices without a laboratory investigation, especially in Eastern Europe and Asia, contribute to the development of new MRSA clones with increased resistance to antibiotics.

Genetic diversity of pvl- positive community-onset methicillin-resistant Staphylococcus aureus isolated at a university hospital in Japan

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is pathogenic to healthy individuals and a significant issue throughout the world. Panton-Valentine leukocidin gene (pvl)-positive sequence type (ST) 8-staphylococcal cassette chromosome (SCC) mec type IV (ST8-IV) as represented by the USA300 clone, is the most prevalent CA-MRSA in many countries. However, the prevalence of pvl-positive CA-MRSA was limited in Japan. Here, we report the incidence of pvl-positive community-onset MRSA (CO-MRSA) isolated from 10 patients seen between 2009 and 2014at a Japanese university hospital. All patients were Japanese and eight cases involved severe skin infections. Antimicrobial susceptibility patterns of the pvl-positive isolates were consistent with those of a typical CA-MRSA clone. Detailed molecular epidemiological analyses showed that three isolates were ST8-IV USA300 clones, whereas the other seven were ST30-IV (three isolates), ST30-I (one isolate), ST59-V (two isolates), and ST1-V (one isolate) clones. No clear difference of infection severity was found between the patients associated with the USA300 clone and those with the other clones. Our findings show that, not only the USA300 clone, but also diverse pvl-positive CO-MRSA clones exist in the community and cause severe skin infections in Japan.

Genomic analysis of ST88 community-acquired methicillin resistant Staphylococcus aureus in Ghana.

BackgroundThe emergence and evolution of community-acquired methicillin resistant Staphylococcus aureus (CA-MRSA) strains in Africa is poorly understood. However, one particular MRSA lineage called ST88, appears to be rapidly establishing itself as an “African” CA-MRSA clone. In this study, we employed whole genome sequencing to provide more information on the genetic background of ST88 CA-MRSA isolates from Ghana and to describe in detail ST88 CA-MRSA isolates in comparison with other MRSA lineages worldwide.MethodsWe first established a complete ST88 reference genome (AUS0325) using PacBio SMRT sequencing. We then used comparative genomics to assess relatedness among 17 ST88 CA-MRSA isolates recovered from patients attending Buruli ulcer treatment centres in Ghana, three non-African ST88s and 15 other MRSA lineages.ResultsWe show that Ghanaian ST88 forms a discrete MRSA lineage (harbouring SCCmec-IV [2B]). Gene content analysis identified five distinct genomic regions enriched among ST88 isolates compared with the other S. aureus lineages. The Ghanaian ST88 isolates had only 658 core genome SNPs and there was no correlation between phylogeny and geography, suggesting the recent spread of this clone. The lineage was also resistant to multiple classes of antibiotics including β-lactams, tetracycline and chloramphenicol.DiscussionThis study reveals that S. aureus ST88-IV is a recently emerging and rapidly spreading CA-MRSA clone in Ghana. The study highlights the capacity of small snapshot genomic studies to provide actionable public health information in resource limited settings. To our knowledge this is the first genomic assessment of the ST88 CA-MRSA clone.

Recurrent furunculosis caused by a community-acquired Staphylococcus aureus strain belonging to the USA300 clone.

A 24-year-old female with recurrent skin and soft tissue infections (SSTI) was enrolled as part of a multicenter observational cohort study conducted by a practice-based research network (PBRN) on community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). Strains were characterized by pulsed-field gel electrophoresis (PFGE), spa typing, and multilocus sequence typing. MRSA strains were analyzed for SCCmec type and the presence of the Panton-Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME) using PCR. In the first episode, S. aureus was recovered from the wound and inguinal folds; in the second, S. aureus was recovered from a lower abdomen furuncle, inguinal folds, and patellar fold. Molecular typing identified CA-MRSA clone USA300 in all samples as spa-type t008, ST8, SCCmecIVa, and a typical PFGE pattern. The strain carried virulence genes pvl and ACME type I. Five SSTI episodes were documented despite successful resolution by antibiotic treatment, with and without incision and drainage. The source of the USA300 strain remains unknown. The isolate may represent a persistent strain capable of surviving extensive antibiotic pressure or a persistent environmental reservoir may be the source, possibly in the patient's household, from which bacteria were repeatedly introduced into the skin flora with subsequent infections.

Clinical and molecular characteristics of community-acquired methicillin-resistant Staphylococcus aureus infections in Chinese neonates.

This study aims to characterize the clinical features of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections in Chinese neonates, as well as the molecular characteristics and expression of key virulence genes of isolates. Clinical information and molecular characteristics of 130 cases were analyzed. Up to 83.8% patients were affected with late-onset infection. Cesarean delivery was the main delivery route, accounting for 74.6% of the total deliveries. Pneumonia (69, 53.1%) was the most common infection. A total of 38 patients (29.2%) suffered from complications. Moreover, 35 cases (26.9%) were invasive infections, among which 88.6% involved multiple organs and 45.7% suffered from complications. Cesarean section and premature birth were the risk factors for invasive CA-MRSA infection. ST59-MRSA-SCCmecIVa-t437 (54, 41.5%) was the most predominant CA-MRSA clone. The hla expression in the ST59 isolates was higher than that in ST910 (p = 0.02) and the hla expression in ST59-SCCmecV-t437 was higher than that in ST59-SCCmecIVa-t437. Approximately, 46.4% (13/28) of the infections caused by ST59-SCCmecV were invasive. This value is higher than that of ST59-SCCmecVa caused infections (14/59, 23.7%) (p = 0.03). This study showed that neonatal CA-MRSA infections in China readily become invasive, involve multiple organs, and are often accompanied by complications. The SCCmec V clone may be more pathogenic than the SCCmecVIa clone.

Emergence of the European ST80 clone of community-associated methicillin-resistant Staphylococcus aureus as a cause of healthcare-associated infections in Eastern Algeria

AimsThe authors had for aim to assess whether an in-hospital spread of the European community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clone was on-going in Annaba, Eastern Algeria. Material and methodsWe carried out a molecular epidemiological study of S. aureus strains causing infections in 4 hospitals located in Annaba, between February and October 2010. ResultsOur study revealed a very low healthcare-associated MRSA (HCA-MRSA) infection incidence rate of 0.34 per 1000 patient-days. However, the rates of HCA-MRSA strains (85/119) and CA-MRSA (7/29) among S. aureus strains are much higher than those found in France. The European CA-MRSA clone (clonal complex 80, Staphylococcal Cassette Chromosome mec IVc, spa type t044, lukS/F-PV-positive) accounted for 14.1% of all healthcare-associated (HCA) MRSA infections. ConclusionThis study confirmed the emerging role of CA-MRSA as HCA pathogens in North-African Africa.

Systemic CA-MRSA infection following trauma during soccer match in inner Brazil: clinical and molecular characterization

Even though community-acquired methicillin resistant Staphylococcus aureus (CA-MRSA) was described a decade ago, reports from Brazil are scarce and cases occurred in large urban centers. We report MRSA sepsis in a 16-year-old male from a small town and who had no history of exposure to healthcare or recent travel. After trauma during a soccer match, he presented swelling in the right thigh, which evolved in a month to cellulitis complicated by local abscess, orchitis and pneumonia. The patient presented severe sepsis, with fever and respiratory failure. Laboratory findings included blood leukocyte counts above 40,000/mm3 and thrombocytopenia. He was submitted to mechanical ventilation and therapy with vancomycin and imipenem. He had a slow but favorable response to therapy and was discharged after six weeks of hospitalization. MRSA grew from blood cultures and respiratory aspirates obtained before antimicrobial therapy. The isolate belonged to sequence type 5, spa type t311, harbored SCCmec type IV and genes for Panton-Valentine leukocidin and Enterotoxin A. The pulsed-field gel electrophoresis pattern was distinct from North American classic CA-MRSA clones. However, the sequence type and the spa type revealed that the clone belong to the same clonal complex isolated in Argentina. This is the first CA-MRSA infection reported in that region, with significant epidemiologic and clinical implications.

Effects of subinhibitory concentrations of antibiotics on virulence factor expression by community-acquired methicillin-resistant Staphylococcus aureus

To examine the effect of subinhibitory concentrations (sub-MICs) of antistaphylococcal drugs on Panton-Valentine leucocidin (PVL), α-haemolysin (Hla) and protein A (SpA) expression by community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). Five clinical isolates representing the main worldwide CA-MRSA clones were grown with sub-MICs (1/8, 1/4 and 1/2 MIC) of five antibiotics (clindamycin, daptomycin, linezolid, tigecycline and vancomycin). After 4 and 6 h of incubation, culture pellets were used for relative quantitative RT-PCR with primers specific for pvl, hla, spa and gyrB. The PVL, Hla and SpA concentrations were measured in the supernatant (for PVL and Hla) and in the cell pellet (for SpA) using specific ELISAs. For all strains tested, clindamycin and linezolid dramatically reduced mRNA levels of PVL and SpA. Tigecycline also decreased the PVL and SpA mRNA levels of 3/5 and 4/5 strains tested, respectively, whereas daptomycin and vancomycin had no significant effect. PVL and SpA quantification confirmed the concentration-dependent inhibition of PVL and SpA production by clindamycin and, to a lesser extent, by linezolid and tigecycline. Only clindamycin decreased Hla mRNA expression, whereas linezolid, tigecycline and daptomycin showed heterogeneous strain-dependent results, and vancomycin had no significant effect. Analysis of the Hla level revealed a stronger concentration-dependent inhibition of Hla release by clindamycin than by linezolid. The effect of sub-MICs on virulence expression depended on the antibiotic and the virulence factor. Clindamycin and linezolid consistently suppressed the expression of different virulence factors by CA-MRSA, whereas tigecycline specifically suppressed PVL expression. Daptomycin and vancomycin seem to have no significant effects at these concentrations.

Methicillin-resistant Staphylococcus aureus ST30-SCCmec IVc clone as the major cause of community-acquired invasive infections in Argentina

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have become a major concern worldwide. We conducted a prospective multicenter study of invasive CA-MRSA to evaluate clinical features and genotype of strains causing invasive infections in Argentina. A total of 55 patients with invasive CA-MRSA infections were included. Most patients (60%) had bloodstream infections, 42% required admission to intensive care unit and 16% died. No CA-MRSA isolates were multiresistant (resistant ⩾3 classes of antibiotics). All isolates carried Panton-Valentine leukocidin (PVL) genes and staphylococcal cassette chromosome (SCCmec) type IV. The majority CA-MRSA strains belonged to ST30 and had identical pulsed-field gel electrophoresis (PFGE) patterns, qualifying as a clonal dissemination of a highly transmissible strain. The main clone recovered from patients with CA-MRSA invasive infections was genotyped as pulsed-field gel electrophoresis type C-ST30, SCCmec type IVc-spa type 019, PVL positive. It has become predominant and replaced the previously described CA-MRSA clone (PFGE type A, ST5, SCCmec type IV, spa type 311).

DNA microarray-based characterisation of Panton–Valentine leukocidin-positive community-acquired methicillin-resistant Staphylococcus aureus from Italy

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) isolates are widespread in many countries, with varying distribution and epidemiology. The aim of this study was to collect and characterise the CA-MRSA isolates circulating in Italy, since only some case reports have been published. Eighteen Panton-Valentine-positive CA-MRSA isolates were collected from different Italian hospitals during the period 2005-2009 from severe infections (skin and soft tissue infections, n = 10; necrotising pneumonia, n = 7; and sepsis, n = 1). Accessory gene regulator (agr) typing, staphylococcal cassette chromosome (SCC) mec typing, spa typing, multi-locus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE) and DNA microarray were applied to categorise isolates into clones and to compare the relevant genetic features of each clone. Six different clones were identified, the most common (7 out of 18 isolates, 38.8%) being agrI/ST8/SCCmecIV, corresponding to the USA300 clone. Six out of the seven USA300 isolates did not harbour the arginine catabolic mobile element (ACME). Four strains (22.2%) were agrIII/ST80/SCCmecIV, corresponding to the European clone. Two of the other clones, namely, agrIII/ST88/SCCmecV and agrIII/ST772/SCCmecV, corresponded to CA-MRSA clones rarely found in other countries and probably originating from Africa or the Indian subcontinent. The results of microarray hybridisations showed that the distribution of resistance genes and other virulence factors was specific to each clone. Some characteristics could be exploited as specific markers for a clone or a group of isolates, e.g. the mer operon, recovered only in ACME-negative USA300 strains. DNA microarray contributed to a more complete description of the variety of different CA-MRSA clones circulating in Italy.

Prevalence and characterization of methicillin-resistant Staphylococcus aureus among healthy children in a city of Argentina

Community acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is a major global problem. Healthy carriers of S. aureus strains have an important role in the dissemination of this bacterium. The aim of this study was to estimate the prevalence of S. aureus and methicillin-resistant S. aureus (MRSA) carriage among healthy children in a city of Buenos Aires province, Argentina, and to determine the potential risk factors for its acquisition. We also described the molecular features of MRSA strains circulating in this population. S. aureus carriage was investigated in all children attending the last year of kindergarten during the 2008 school- year period. Household contacts of MRSA carriers were also screened. Of 316 healthy children, 98 (31.0%) carried S. aureus, including 14 MRSA carriers (4.4%) and 84 methicillin susceptible S. aureus (MSSA) carriers (26.6%). All MRSA isolates carried the SCC mec type IV cassette. Eight of the fourteen isolates were closely related to the clone responsible for most severe community-acquired MRSA infections caused in our country (CAA: PFGE A, SCC mec IV, spa t311, ST5). Two subtypes (A 1 and A 2) were distinguished in this group by PFGE. Both had agr type II and presented the same virulence determinants, except for PVL coding genes and sea that were only harbored by subtype A 1. Our results, based on the analysis of MRSA isolates recovered in the screening of healthy children, provide evidence of a community reservoir of the major CA-MRSA clone described in Argentina.

World Health Day 2011–Antimicrobial Resistance: No Action Today, No Cure Tomorrow

The World Health Organization (WHO) has recently announced that the global phenomenon of antimicrobial resistance will be the theme of World Health Day 2011.1 The campaign, which aims to safeguard medicines for future generations, will call on governments around the world to implement policies to prevent the emergence of highly resistant “superbugs”.1,2 Asia remains the epicenter of resistant superbugs.3,4 In Taiwan, there is an alarmingly high prevalence of penicillin-resistant Streptococcus pneumoniae, community-acquired and hospitalacquired methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae, multidrug-resistant and extensively drug-resistant Pseudomonas aeruginosa and Acinetobacter baumannii, as well as penicillinand fluoroquinolone-resistant Neisseria gonorrhoeae. Fluoroquinolone-resistant E coli and Salmonella species, particularly S enterica serotype Choleraesuis, are found not only in humans but also in animals. Azole-resistant Candida species, especially C glabrata, are prevalent in hospitals throughout Taiwan.3,4 In addition, the persistence of multidrug-resistant and the emergence of extensively drug-resistant Mycobacterium tuberculosis pose great challenges to public health.3 Community-acquired MRSA clones including ST59-MRSA-SCCmec type IV-spa type t437, ST30MRSA-SCCmec type IV-spa type t019, and ST72MRSA-SCCmec type IV-spa type t324 predominate in Asian countries. Previously established hospitalacquired MRSA strains including sequence type (ST)239 and ST5 clones have been found among community-acquired MRSA isolates from patients without any risk factors for hospital-acquired MRSA infection. Community-acquired MRSA clones such as ST59, ST30, and ST72 have also been isolated from patients with hospital-acquired infections.5 Various MRSA clones have spread between the community and hospitals as well as between countries.5 A few extensively drug-resistant A baumannii clones have disseminated throughout most hospital settings in Asia.3,4 Even more alarming is the recent emergence in Taiwan of carbapenemresistant Enterobacteriaceae, including those possessing New Delhi metallo-β-lactamase-1 and K pneumoniae carbapenemase.6 Antimicrobial resistance has struck at the core of infectious disease control worldwide.1,2 Although antimicrobial-resistant pathogens can be found throughout the world, antimicrobial resistance is of particular concern in countries where prescription of antimicrobial agents is unregulated and where antibiotics are widely available over the counter. The increased use of antibiotics in the

High prevalence of methicillin-resistant Staphylococcus aureus clone ST80-IV in hospital and community settings in Algiers

AbstractUSA300 is an epidemic community-acquired methicillin-resistant Staphylococcus aureus (C-MRSA) clone in the USA, whereas the European C-MRSA clone ST80-IV has mainly a sporadic diffusion in Europe. The prevalence of European clone ST80-IV in Algeria is poorly documented. We prospectively studied S. aureus infections at Mustapha Bacha hospital in Algiers over a 20-month period. S. aureus nasal colonization was studied during a further 6-month period. The European clone ST80-IV was responsible for more than one-third of both community infections (35.7%) and hospital infections (35.8%). Panton–Valentine leukocidin (PVL)-positive MRSA isolated from hospital inpatients were resistant to multiple antibiotics, including fluoroquinolones in 44.9% of cases. The PVL-positive MRSA nasal carriage rate was high among patients and staff in the dermatology unit (8.7% and 18.5%, respectively), but low (2.7%) among patients attending the outpatient clinic. The European PVL-positive C-MRSA clone ST80-IV is widespread in the Algiers hospital and community settings.

Molecular Characteristics of Community-Acquired Methicillin-ResistantStaphylococcus aureusin Hokkaido, Northern Main Island of Japan: Identification of Sequence Types 6 and 59 Panton-Valentine Leucocidin–Positive Community-Acquired Methicillin-ResistantStaphylococcus aureus

Prevalence and molecular characteristics of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) were studied in Hokkaido, the main northern island of Japan. Among the 1,015 S. aureus isolates derived from clinical specimens of outpatients collected in 2009, methicillin resistance gene mecA was detected in 189 isolates (18.6%). The most frequent staphylococcal cassette chromosome mec (SCCmec) type in MRSA was II (83.1%), followed by IV (6.9%) and V (3.2%). MRSA with type II-SCCmec showed multiple drug resistance and harbored various toxin and virulence factor genes except for Panton-Valentine leucocidin (PVL) gene. These isolates were mostly classified into sequence type 5 (ST5) (or other STs in CC5) and coagulase genotype II and were thus genetically similar to hospital-acquired MRSA, which have been predominating in Japan (New York/Japan clone). PVL gene was detected in three MRSA strains belonging to ST6 (two strains) and ST59 (one strain), having type IVa- and Vt-SCCmec, respectively, and also in two methicillin-susceptible S. aureus ST121 and ST188. The arcA gene within the arginine catabolic mobile element (ACME) was detected in the two PVL-negative ST5 MRSA strains, which had type IIa- or V-SCCmec. The PVL gene-positive ST6 and ST59 CA-MRSA strains were susceptible to more antimicrobials and had less virulence factor genes than the PVL-negative ST5 MRSA, including the ACME-arcA-positive strains. In the present study, ST6 was identified as a lineage of PVL-positive CA-MRSA, the ACME-arcA was first detected in ST5 MRSA with type V-SCCmec, and ST59 Taiwanese CA-MRSA strain was isolated in Hokkaido for the first time. These findings suggest a potential spread of these emerging CA-MRSA clones in Japan.

Panton-Valentine Leukocidin-Positive and Toxic Shock Syndrome Toxin 1-Positive Methicillin-Resistant Staphylococcus aureus : a French Multicenter Prospective Study in 2008

The epidemiology of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) differs from country to country. We assess the features of the ST80 European clone, which is the most prevalent PVL-positive CA-MRSA clone in Europe, and the TSST-1 ST5 clone that was recently described in France. In 2008, all MRSA strains susceptible to fluoroquinolones and gentamicin and resistant to fusidic acid that were isolated in 104 French laboratories were characterized using agr alleles, spa typing, and the staphylococcal cassette chromosome mec element and PCR profiling of 21 toxin genes. Three phenotypes were defined: (i) kanamycin resistant, associated with the ST80 clone; (ii) kanamycin and tobramycin resistant, associated with the ST5 clone; and (iii) aminoglycoside susceptible, which was less frequently associated with the ST5 clone. Among the 7,253 MRSA strains isolated, 91 (1.3%) were ST80 CA-MRSA (89 phenotype 1) and 190 (2.6%) were ST5 CA-MRSA (146 phenotype 2, 42 phenotype 3). Compared to the latter, ST80 CA-MRSAs were more likely to be community acquired (80% versus 46%) and found in young patients (median age, 26.0 years versus 49.5 years) with deep cutaneous infections (48% versus 6%). They were less likely to be tetracycline susceptible (22% versus 85%) and to be isolated from respiratory infections (6% versus 27%). The TSST-1 ST5 clone has rapidly emerged in France and has become even more prevalent than the ST80 European clone, whose prevalence has remained stable. The epidemiological and clinical patterns of the two clones differ drastically. Given the low prevalence of both among all staphylococcal infections, no modification of antibiotic recommendations is required yet.

Clinical manifestations and outcome of skin infections caused by the community‐acquired methicillin‐resistant Staphylococcus aureus clone ST80‐IV

Several Panton-Valentin leukocidin-positive clones of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) are spreading worldwide. The European clone ST80-IV is the main CA-MRSA clone in Europe. There is no reported study of the specific clinical manifestations and outcome of skin infections caused by the clone ST80-IV, using strict definitions of skin diseases. Single-centre observational prospective cohort of S. aureus skin infections caused by the clone ST80-IV. From November 1999 to October 2009, we diagnosed skin infections due to the clone ST80-IV in 20 patients (median age 28 years, median 27; range 1-66). All the isolates had all the following characteristics: lukPV, etd and edin gene-positive, agr 3 allele, spa-type t044 and ST80. All the isolates were resistant to beta-lactam agents, kanamycin, tetracycline and fusidic acid. During the study period, the 20 patients had the following manifestations: 19 primary abscesses (18 single abscess and one patient with two), eight furuncles, four folliculitis, one case of cellulitis, one wound infection and one felon. Surgical treatment and drainage was required for all the primary abscesses. The infections occurred mainly in the perineal area (50%). No secondary infections occurred in family members. Despite strict hygiene measures, systemic antibiotics and nasal mupirocine, four patients (20%) had recurrent skin infections over a period of a few months to 6 years. The CA-MRSA clone ST80-IV is responsible for suppurative skin infections such as furuncles and abscesses, which can recur over a period of several years.