Epidemiology Of Community-associated Methicillin-resistant Staphylococcus Aureus Research Articles

Genomic Epidemiology of CC30 Methicillin-Resistant Staphylococcus aureus Strains from Argentina Reveals Four Major Clades with Distinctive Genetic Features.

ABSTRACTStaphylococcus aureus clonal complex 30 (CC30) has given rise to epidemics worldwide and is one of the most prevalent lineages in Argentina, represented by sequence type 30 methicillin-resistant S. aureus SCCmec type IV (ST30-MRSA-IV). ST30-MRSA-IV has displaced previous prevalent clones in the country and demonstrated increased virulence. Despite the burden of infections caused by ST30-MRSA-IV both in hospitals and in communities in Argentina, no detailed genome-based characterization of this clone is available to date. In this study, we used whole-genome sequencing (WGS) to evaluate the genetic diversity, population structure, and genomic characteristics of 190 CC30-MRSA strains circulating in Argentina between 2004 and 2015. Phylogenetic analysis revealed the existence of 4 major clades: ARG-1 (CC30-MRSA-IVc-spa t012), ARG-2 (ST30-MRSA-IVc-spa t021 related), ARG-3 (ST30-MRSA-IVh/j-spa t021 and related), and ARG-4 (CC30-MRSA-IVc-spa t019 and related). The clades were characterized by different distributions of antimicrobial resistance determinants, virulence genes, and mobile genetic elements (MGEs). While ARG-1 and ARG-4 were related to global epidemic MRSA-16 (EMRSA-16) and South West Pacific (SWP) clones, respectively, ARG-3 was phylogenetically distinct from previously defined CC30 epidemic clones. ARG-4, the most prevalent and geographically disseminated in the collection (N = 164), was characterized by specific MGEs and chromosomal mutations that might have contributed to its virulence and success. To our knowledge, this is the first genomic epidemiology study of CC30-MRSA in Argentina, which will serve as baseline genomic data going forward to inform public health measures for infection prevention and control.IMPORTANCE The rise in prevalence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is of public health concern. In Argentina, several studies documented a shift in the epidemiology of CA-MRSA since 2009, with clonal complex 30 (CC30) and, in particular, sequence type 30 MRSA SCCmec type IV (ST30-MRSA-IV) replacing other clones both in communities and in hospitals and possibly displaying increased virulence. By sequencing the whole genomes of 190 CC30 MRSA isolates recovered from Argentina between 2005 and 2015, we showed that they represented a diverse population composed of 4 major clades. The predominant clade evolved from the South West Pacific clone but has acquired a distinct repertoire of mobile genetic elements, virulence genes, and chromosomal mutations that might play a role in its success. Our work is the first extensive genomic study of CC30 S. aureus in Argentina and will contribute not only to the development of genomic surveillance in the region but also to our understanding of the global epidemiology of this pathogen.

Methicillin resistant Staphylococcus Aureus in emergency department patients in the United Arab Emirates

BackgroundSince the 1990s, community-associated methicillin resistant staphylococcus aureus (CA-MRSA) has emerged as an important global cause of skin and soft tissue infections. Little is known about the epidemiology of this pathogen in the Middle East.MethodsWe conducted a prospective observational study in a single large teaching hospital in Dubai to identify the incidence of community-acquired methicillin resistant staphylococcus aureus (MRSA) among ambulatory patients presenting with purulent skin and soft tissue infections. We performed wound cultures and administered standard questionnaires to 100 cases presenting to the emergency department. Bivariate and multivariate analyses were performed to identify risk factors for MSRA versus other pathogens.ResultsThe prevalence of MRSA was 23% (18/78) among 78 culture-positive isolates and 29% (18/62) among Staphylococcus-positive isolates. 74% received antibiotics of which 4/74 (5%) received antibiotics appropriate for CA-MRSA infections. Multivariate adjusted analysis identified playing contact sports (OR 5.9 [95% CI 1.3–27.1]) and female sex (OR 6.3 [95% CI 1.6–24.8]) as independent risks for MRSA infection.ConclusionsThis is the first study to describe the epidemiology of CA-MRSA in the ambulatory setting in the Middle East and demonstrates a substantial proportion of cases presenting with skin and soft tissue infections were CA-MRSA. Although most skin and soft tissue infections are abscesses for which the cornerstone of treatment is high quality incision and drainage, if adjunct antibiotics are prescribed in this setting, CA-MRSA-active antibiotics should be considered.

Community-associated methicillin-resistant Staphylococcus aureus infections in Aboriginal children attending hospital emergency departments in a regional area of New South Wales, Australia: a seven-year descriptive study.

ObjectiveCommunity-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) can cause bacterial skin infections that are common problems for Aboriginal children in New South Wales (NSW). MRSA is not notifiable in NSW and surveillance data describing incidence and prevalence are not routinely collected. The study aims to describe the epidemiology of CA-MRSA in Aboriginal children in the Hunter New England Local Health District (HNELHD).MethodsWe linked data from Pathology North Laboratory Management System (AUSLAB) and the HNELHD patient administration system from 33 hospital emergency departments. Data from 2008–2014 for CA-MRSA isolates were extracted. Demographic characteristics included age, gender, Aboriginality, rurality and seasonality.ResultsOf the 1222 individuals in this study, 408 (33.4%) were Aboriginal people. Aboriginal people were younger with 45.8% aged less than 10 years compared to 25.9% of non-Aboriginal people. Most isolates came from Aboriginal people who attended the regional Tamworth Hospital (193/511 isolates from 149 people). A larger proportion of Aboriginal people, compared to non-Aboriginal people, resided in outer regional (64.9% vs 37.2%) or remote/very remote areas (2.5% vs 0.5%). Most infections occurred in summer and early autumn. For Aboriginal patients, there was a downward trend through autumn, continuing through winter and spring.DiscussionAboriginal people at HNELHD emergency departments appear to represent a greater proportion of people with skin infections with CA-MRSA than non-Aboriginal people. CA-MRSA is not notifiable in NSW; however, pathology and hospital data are available and can provide valuable indicative data to health districts for planning and policy development.

The Dominant Australian Community-Acquired Methicillin-Resistant Staphylococcus aureus Clone ST93-IV [2B] Is Highly Virulent and Genetically Distinct

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) USA300 has spread rapidly across North America, and CA-MRSA is also increasing in Australia. However, the dominant Australian CA-MRSA strain, ST93-IV [2B] appears distantly related to USA300 despite strikingly similar clinical and epidemiological profiles. Here, we compared the virulence of a recent Australian ST93 isolate (JKD6159) to other MRSA, including USA300, and found that JKD6159 was the most virulent in a mouse skin infection model. We fully sequenced the genome of JKD6159 and confirmed that JKD6159 is a distinct clone with 7616 single nucleotide polymorphisms (SNPs) distinguishing this strain from all other S. aureus genomes. Despite its high virulence there were surprisingly few virulence determinants. However, genes encoding α-hemolysin, Panton-Valentine leukocidin (PVL) and α-type phenol soluble modulins were present. Genome comparisons revealed 32 additional CDS in JKD6159 but none appeared to encode new virulence factors, suggesting that this clone's enhanced pathogenicity could lie within subtler genome changes, such as SNPs within regulatory genes. To investigate the role of accessory genome elements in CA-MRSA epidemiology, we next sequenced three additional Australian non-ST93 CA-MRSA strains and compared them with JKD6159, 19 completed S. aureus genomes and 59 additional S. aureus genomes for which unassembled genome sequence data was publicly available (82 genomes in total). These comparisons showed that despite its distinctive genotype, JKD6159 and other CA-MRSA clones (including USA300) share a conserved repertoire of three notable accessory elements (SSCmecIV, PVL prophage, and pMW2). This study demonstrates that the genetically distinct ST93 CA-MRSA from Australia is highly virulent. Our comparisons of geographically and genetically diverse CA-MRSA genomes suggest that apparent convergent evolution in CA-MRSA may be better explained by the rapid dissemination of a highly conserved accessory genome from a common source.

Epidemiology and surveillance of methicillin-resistant staphylococcus aureus in Latin America

Surveillance systems monitoring the spread and divergence of methicillin-resistant Staphylococcus aureus (MRSA) strains are critical if preventive and therapeutic measures targeting MRSA infection are to be employed optimally. Surveillance provides information on the spread of MRSA, on the emergence of new strains within hospitals and communities, on the antibiotic resistance profile and virulence of strains, and on the risk factors associated with infection. These data help clinicians to provide appropriate empiric treatment of infections circulating in their region, leading to improved patient outcomes. While information on MRSA epidemiology in Latin America is growing, significant gaps exist in the available data, especially in local areas where fewer resources are available for characterizing and reporting MRSA strains. Here, we describe current knowledge of healthcare- and community-associated MRSA epidemiology in the region, and provide recommendations for future development of surveillance systems with a view to providing robust data at regional, national and local levels.

Invasive community-associated MRSA infections: epidemiology and antimicrobial management

Importance of the field: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is now a predominant cause of infections in the community and is adding to the overwhelming MRSA burden in the hospital setting. CA-MRSA is most commonly noted as a prominent pathogen in skin and soft tissue infections (SSTI) but has been increasingly described in more invasive disease. New developments in the epidemiology and treatment of CA-MRSA have emerged to improve the understanding of this disease.Areas covered in this review: We present the latest epidemiologic and clinical treatment studies of CA-MRSA in a variety of infection types. The methods used involve a comprehensive literature search of the previous 10 years, including a detailed focus on new literature in the last 5 years. The search terms used were ‘CA-MRSA epidemiology’, ‘S. aureus resistance’, ‘CA-MRSA treatment’, and ‘S. aureus virulence’.What the reader will gain: An in-depth understanding of the changing epidemiology of CA-MRSA and management of SSTI and more invasive infections with this pathogen. Adjunctive and alternative therapies are also reviewed.Take home message: The epidemiology of CA-MRSA is rapidly evolving. Increasing multi-drug resistance along with virulence factors associated with this serious disease complicate its treatment. Additional clinical trials are needed to select optimal regimens in the treatment of invasive CA-MRSA infections.

Community-associated methicillin-resistant Staphylococcus aureus infections

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has been recognized for over a decade, and usually refers to MRSA identified in previously healthy individuals with no recognized MRSA risk factors. Infections range from minor skin and soft tissue infections, through to severe pneumonia and necrotizing fasciitis. This review summarizes the current data on the epidemiology and molecular features of CA-MRSA, in addition to diagnosis and therapeutic measures. We also refer to current national guidelines for the management of these infections. Areas of agreement include the important genotypic and phenotypic differences of community MRSA strains compared with hospital strains. Areas of controversy include the precise epidemiological definition of community-acquired/associated MRSA. Fortunately, true CA-MRSA can be differentiated from hospital MRSA by molecular techniques, as discussed herein. Recent interest has focused on the changing epidemiology of CA-MRSA. Worldwide, CA-MRSA is now seen outside of the initial specific population groups, and in the USA, the successful USA300 community strain is beginning to spread back into hospitals. Reasons why USA300 remains relatively uncommon in Europe are unclear. Topics timely for research include the investigation of the epidemiology of infections and evolutionary genomics.

Epidemiology and Virulence of Community-Associated MRSA

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) emerged unexpectedly in the 1990s and is now a problem worldwide. CA-MRSA is epidemic in the United States and is the most common cause of community-associated bacterial infections. Here, we provide a basic overview of CA-MRSA epidemiology and discuss molecules that contribute to the enhanced virulence phenotype of this pathogen.

Community-associated methicillin-resistant Staphylococcus aureus: prevalence in skin and soft tissue infections at emergency departments in the Greater Toronto Area and associated risk factors

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), which is caused primarily by the Canadian methicillin-resistant Staphylococcus aureus-10 (CMRSA-10) strain (also known as the USA300 strain) has emerged rapidly in the United States and is now emerging in Canada. We assessed the prevalence, risk factors, microbiological characteristics and outcomes of CA-MRSA in patients with purulent skin and soft tissue infections (SSTIs) presenting to emergency departments (EDs) in the Greater Toronto Area. Patients with Staphylococcus aureus SSTIs who presented to 7 EDs between Mar. 1 and Jun. 30, 2007, were eligible for inclusion in this study. Antimicrobial susceptibilities and molecular characteristics of MRSA strains were identified. Demographic, risk factor and clinical data were collected through telephone interviews. MRSA was isolated from 58 (19%) of 299 eligible patients. CMRSA-10 was identified at 6 of the 7 study sites and accounted for 29 (50%) of all cases of MRSA. Telephone interviews were completed for 161 of the eligible patients. Individuals with CMRSA-10 were younger (median 34 v. 63 yr, p = 0.002), less likely to report recent antibiotic use (22% v. 67%, p = 0.046) or health care-related risk factors (33% v. 72%, p = 0.097) and more likely to report community-related risk factors (56% v. 6%, p = 0.008) than patients with other MRSA strains. CMRSA-10 SSTIs were treated with incision and drainage (1 patient), antibiotic therapy (3 patients) or both (5 patients), and all resolved. CMRSA-10 isolates were susceptible to clindamycin, tetracycline and trimethoprim-sulfamethoxazole. CA-MRSA is a significant cause of SSTIs in the Greater Toronto Area, and can affect patients without known community-related risk factors. The changing epidemiology of CA-MRSA necessitates further surveillance to inform prevention strategies and empiric treatment guidelines.

Community-Associated Methicillin-Resistant Staphylococcus aureus: Trends in Case and Isolate Characteristics from Six Years of Prospective Surveillance

In 2000, the Minnesota Department of Health (MDH) implemented active, sentinel site surveillance for community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). Data from 2000-2005 were analyzed to determine trends in case characteristics, pulsed-field types (PFTs), and antimicrobial susceptibilities including inducible clindamycin resistance (ICR). Active sentinel site surveillance was initiated in 2000 at 12 hospital laboratories that served inpatients and outpatients. Patient medical records were reviewed to determine if they met the epidemiologic case criteria for CA-MRSA; isolates were obtained from patients meeting these criteria. The MDH Public Health Laboratory performed pulsed-field gel electrophoresis subtyping and antimicrobial susceptibility testing, including ICR. The proportion of MRSA cases classified as CA increased from 11% to 33% (p<0.01). The proportion of cases with skin or soft tissue infections also increased compared with other infection types from 75% to 87% (p<0.01). During the surveillance period, USA300 replaced USA400 as the dominant PFT. With the change in dominant PFT, the proportion of isolates susceptible to erythromycin (45% to 13%, p<0.01) and ciprofloxacin (80% to 59%, p<0.01) decreased. The proportion of erythromycin-resistant/clindamycin-susceptible isolates with ICR (93% to 14%, p<0.01) decreased. The proportion of susceptible isolates also changed within the USA300 PFT; the proportion of isolates susceptible to erythromycin (33% vs. 3%) and the proportion susceptible to ciprofloxacin (67% to 62%) decreased significantly. CA-MRSA increased dramatically from 2000 to 2005. Changes in the predominant PFT have impacted susceptibility profiles of CA-MRSA, including ICR. Continued surveillance is needed to monitor the changing epidemiology of CA-MRSA and to inform clinical decisions.

Comparison of community-associated meticillin-resistant Staphylococcus aureus from teaching hospitals in London and the USA, 2004–2006: where is USA300 in the UK?

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is increasingly common in the USA, but rare in the UK. We compared CA-MRSA from the UK and USA to examine differences in the molecular epidemiology. We investigated patients presenting with MRSA in the first 72 h of hospital admission or in out-patient settings in a UK and a US hospital from January 2004 to March 2006. Fluoroquinolone susceptibility was used as a screening marker to select presumptive CA-MRSA. One hundred and eighteen and 49 such strains were identified, representing a prevalence of 0.1 and 0.2 isolates per 1,000 patient days in the UK and US respectively. Panton-Valentine leukocidin (PVL)-positive ST8-IVa (USA300)-type strains predominated among 43 surviving US isolates, whereas PVL-negative ST1-IVa predominated among 71 surviving UK isolates. There are striking differences between the molecular epidemiology of CA-MRSA in UK and US hospitals, which may have implications for control.

Comparison of Community-Associated and Health Care-Associated Methicillin-ResistantStaphylococcus aureusin Canada: Results from CANWARD 2007

BACKGROUND: Community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) differ from health care-associated MRSA (HA-MRSA) in their genotypic and phenotypic characteristics. The purpose of the present study was to compare the demographics, antimicrobial susceptibilities and molecular epidemiology of CA-MRSA and HA-MRSA in Canada. METHODS: In 2007, 385 MRSA isolates were collected from Canadian patients attending hospital clinics, emergency rooms, medical/ surgical wards and intensive care units. Susceptibilities to betalactams, clarithromycin, clindamycin, daptomycin, levofloxacin, linezolid, moxifloxacin, tigecycline, trimethoprim-sulfamethoxazole and vancomycin were determined by Clinical and Laboratory Standards Institute broth microdilution. Strain typing was performed by pulsed-field gel electrophoresis (PFGE) and themecA,nucandpvlgenes were detected by polymerase chain reaction. RESULTS: Of the 385 MRSA, 19.5% were CA-MRSA and 79.2% were HA-MRSA as determined by PFGE. CA-MRSA belonged to PFGE types CMRSA10/USA300 (66.7%) and CMRSA7/USA400 (33.3%); PFGE types identified among HA-MRSA included CMRSA2/USA100/800 (81.6%), CMRSA6 (13.1%), CMRSA1/ USA600 (3.3%), CMRSA5/USA500 (1.3%), CMRSA3 (0.3%) and CMRSA9 (0.3%). Panton-Valentine leukocidin (PVL) was detected in 94.7% of CA-MRSA and 0.7% of HA-MRSA. Resistance rates (CA-MRSA versus HA-MRSA) were 61.3% versus 97.7% to levofloxacin, 73.3% versus 96.7% to clarithromycin, 12.0% versus 74.8% to clindamycin and 0.0% versus 15.4% to trimethoprim-sulfamethoxazole. No MRSA were resistant to vancomycin, linezolid, tigecycline or daptomycin. CONCLUSIONS: CA-MRSA represented 19.5% of all MRSA. CA-MRSA was significantly more susceptible to levofloxacin, clarithromycin, clindamycin and trimethoprim-sulfamethoxazole than HA-MRSA. Of CA-MRSA, 94.7% were PVL-positive while 99.3% of HA-MRSA were PVL-negative. CA-MRSA is an emerging pathogen in Canadian hospitals.

A survey of community-associated methicillin-resistant Staphylococcus aureus in Korea

Methicillin-resistant Staphylococcus aureus (MRSA), originally restricted to hospitals, has emerged as a significant pathogen in the community. Although MRSA accounts for over 60% of S. aureus in tertiary hospitals in Korea, little is known about the epidemiology of community-associated MRSA (CA-MRSA). From January to July 2005, a hospital laboratory-based survey was conducted in seven community-based or tertiary hospitals. The medical records and Health Insurance Review Agency databases were reviewed and MRSA isolated from patients without apparent risk factors was defined as CA-MRSA. Susceptibilities to 12 antibiotics were tested by the disc diffusion method. SCCmec typing, Panton-Valentine leucocidin (PVL) gene detection and multilocus sequence typing (MLST) were performed according to published protocols. Of 3,251 S. aureus, 1,900 (58.4%) were MRSA. CA-MRSA accounted for 112 (5.9%) of the MRSA. Of the 112 CA-MRSA isolates, 27 and 33 were found to be pathogens and colonizers, respectively. Fifty-two isolates from the patients with chronic otitis media were classified as 'undetermined'. Most of the 27 CA-MRSA patients had skin and soft tissue infections or acute ear infections. None of the patients died during the study period. Among 72 isolates tested, 64% were multidrug-resistant. SCCmec type IVa was the most common type among the colonizers and pathogens. On MLST analysis, ST72 was predominant, but ST5 and ST239 were prevalent in the 'undetermined' group. None possessed the PVL gene. Despite MRSA-endemic hospital settings, CA-MRSA infections are not common in Korea. A new clone of CA-MRSA, ST72-SCCmec type IVa without the PVL gene, is the most common form.

Community-Associated Methicillin-Resistant Staphylococcus aureus Skin and Soft Tissue Infections at a Public Hospital

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have emerged among patients without health care-associated risk factors. Understanding the epidemiology of CA-MRSA is critical for developing control measures. At a 464-bed public hospital in Chicago and its more than 100 associated clinics, surveillance of soft tissue, abscess fluid, joint fluid, and bone cultures for S aureus was performed. We estimated rates of infection and geographic and other risks for CA-MRSA through laboratory-based surveillance and a case-control study. The incidence of CA-MRSA skin and soft tissue infections increased from 24.0 cases per 100,000 people in 2000 to 164.2 cases per 100,000 people in 2005 (relative risk, 6.84 [2005 vs 2000]). Risk factors were incarceration (odds ratio [OR], 1.92; 95% confidence interval [CI], 1.00-3.67), African American race/ethnicity (OR, 1.91; 95% CI, 1.28-2.87), and residence at a group of geographically proximate public housing complexes (OR, 2.50; 95% CI, 1.25-4.98); older age was inversely related (OR, 0.89; 95% CI, 0.82-0.96 [for each decade increase]). Of 73 strains tested, 79% were pulsed-field gel electrophoresis type USA300. Clonal CA-MRSA infection has emerged among Chicago's urban poor. It has occurred in addition to, not in place of, methicillin-susceptible S aureus infection. Epidemiological analysis suggests that control measures could focus initially on core groups that have contributed disproportionately to risk, although CA-MRSA becomes endemic as it disseminates within communities.

Impact of community-associated, methicillin-resistant Staphylococcus aureus on management of the skin and soft tissue infections in children

Skin and soft tissue infections (SSTIs) are common illnesses that have a significant impact on health care management. Community-associated, methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have been documented among healthy individuals without predisposing risk factors. The appearance and spread of CA-MRSA represent a new challenge in pediatric medicine and have important clinical implications for therapy of infections caused by S. aureus. This article provides a review of recent changes in the epidemiology of CA-MRSA, pathogenic potential, and therapeutic considerations in the management of SSTIs in children.

Prevention of Community-Associated Methicillin-Resistant Staphylococcus aureus Infection among Asian/Pacific Islanders: A Qualitative Assessment

BACKGROUND: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has been increasingly reported over the past decade, especially in Asian/Pacific Islanders (A/PIs). Most studies to date have been descriptive and have not identified behavioral risk factors for disease prevention. METHODS: To identify barriers and to better understand how best to reach these individuals with prevention messages, ten ethnographic interviews were conducted in September 2003 in Oahu and Kauai, Hawaii, with A/PIs identified as having CA-MRSA infections. A standardized script was used which included questions on the transmission, treatment, and prevention of CA-MRSA. Data were coded using qualitative methods; non-response to individual questions was not included in the analysis. RESULTS: Respondents were predominantly male (80%), with an age range of 20 to >60 years. Most (70%) thought skin infections were not a new problem in Hawaii; however, 75% (6/8) did feel it was a common problem. Many (70%) were familiar with the term “staph,” but only one recognized the term “MRSA.” Responses varied as to how people (in general) get skin infections versus how they personally acquired the infection and most often included open sores/cuts (30% and 50%, respectively), poor hygiene (30% and 10%), and the ocean (30% and 30%). Perceptions regarding how people (in general) and how respondents personally can prevent infection also focused on hygiene (60% and 30%, respectively) and avoiding bodies of water such as the ocean (30% and 30%). Most (89%, 8/9) attempted to self-treat the infection prior to seeking medical care, using a range of home remedies (63%, 5/8) to store-bought solutions (38%, 3/8). Time to medical treatment ranged from 1 day to several months, with none reporting barriers to treatment. When asked about the best method to receive medical information, 63% (5/8) stated a newspaper/brochure. The preferred and most trusted source, however, was friends and family (70%), especially those employed in healthcare (57%, 4/7). CONCLUSIONS: Potential sources of infection and personal measures for control, including self-treatment, were identified in these ethnographic interviews—information infrequently found in medical records or written surveys. Qualitative assessment allows for the identification of these unique factors and may provide valuable insight into the epidemiology of CA-MRSA.