Investigation of Panton-Valentine leukocidin genes and SCCmec types in clinical Staphylococcus aureus isolates from Turkey

Panton-Valentine leukocidin (PVL) is an important virulence determinant of Staphylococcus aureus. The aim of this study was to investigate the prevalence of PVL genes in clinical S. aureus isolates and to determine the staphylococcal chromosomal cassette mec (SCCmec) types of methicillin-resistant S. aureus (MRSA) strains obtained from inpatients and outpatients of two hospitals in Turkey. Of the 304 S. aureus strains (230 hospital acquired [HA] and 74 community-onset [CO]), 261 were MRSA and 43 were methicillin-sensitive S. aureus (MSSA). PVL positivity was determined in 12 (1 HA and 11 community acquired) strains. Eight were MRSA, and four were MSSA. Seven of the PVL-positive strains were isolated from wound specimens, four from urine, and one from synovial fluid. SCCmec type III (93.78%) was more prevalent among HA-MRSA strains, and SCCmec type IIIB (41.18%) was more prevalent among CO-MRSA strains. Pulsed-field gel electrophoresis patterns of the PVL-positive isolates were different. Our results indicate that PVL-positive strains are able to cause infection in nearly every system without the need for additional risk factors. Our PVL-positive CO-MRSA strains carry SCCmec types other than types IV and V. Due to the presence of PVL-positive strains in the hospitals, it is important to establish appropriate infection control measures to prevent their spread in the community and in hospitals.     

Predominance of staphylococcal cassette chromosome mec (SCCmec) type IV among methicillin-resistant Staphylococcus aureus (MRSA) in a Swedish county and presence of unknown SCCmec types with Panton-Valentine leukocidin genes

Methicillin-resistant Staphylococcus aureus (MRSA) is an established nosocomial pathogen, but has recently begun to appear in the community. The clones in the community may not have originated in the hospital setting, and are referred to as community-acquired MRSA (CA-MRSA). Resistance to methicillin is mediated by the gene mecA, which is carried by the mobile genetic element staphylococcal cassette chromosome mec (SCCmec). SCCmec typing (I-IV) of all clinical isolates of MRSA (n = 92) from 1987 to 2004 in Orebro County, Sweden, was performed by real-time LightCycler PCR to detect the essential genetic components mecA, mecR1, IS1272, ccrA and ccrB. Forty-one isolates harboured type IV SCCmec, of which ten could be classified further as subtype IVa, and 27 as subtype IVc. No isolates belonged to subtype IVb, but four isolates could not be subtyped, and may be examples of novel type IV SCCmec subtypes. Thirty-five MRSA isolates, assigned to six different pulsotypes by pulsed-field gel electrophoresis, did not belong to SCCmec types I-IV. The Panton-Valentine leukocidin (PVL) genes were identified in two of these pulsotypes. Only SCCmec type IV has been associated previously with the PVL toxin, but the results suggest that new PVL-positive clones with novel SCCmec types may be arising and disseminating in the community.     

Dissemination of methicillin-resistant staphylococci among healthy Japanese children

Methicillin-resistant Staphylococcus aureus (MRSA), regarded as a tenacious pathogen in the hospital, has recently become increasingly prevalent as a community pathogen. We evaluated the prevalence and characteristics of methicillin-resistant staphylococci in the Japanese community by testing nasal samples of 818 children of five day care centers and two kindergartens in three districts. We found that methicillin-resistant staphylococci are already prevalent among healthy children. Among 818 children, 35 children (4.3%) carried MRSA and 231 children (28.2%) carried methicillin-resistant coagulase-negative staphylococci (MRC-NS). The types of staphylococcal cassette chromosome mec (SCCmec) found among 44 MRSA isolates were as follows: type IIa, 11 isolates; type IIb, 19 isolates; and type IV, 14 isolates. The type IIb SCCmec element was a new SCCmec element found in this study. Eleven (25%) strains which belonged to clonal complex 5 (CC5) carried type IIa SCCmec, and they produced type 2 coagulase and toxic shock syndrome toxin 1. They were indistinguishable from health care-associated MRSA (H-MRSA) strains in Japan, represented by strain N315. On the other hand, 33 (75%) strains, most of which belonged to CC78 or CC91, carried small SCCmec elements, such as type IIb or type IV, and they produced type 1 or type 3 coagulase and exfoliative toxin. The data indicated that MRSA clones distinct from H-MRSA have disseminated in healthy children. The fact that MRC-NS strains were prevalent in the community suggested that they might serve as a reservoir for the SCCmec element carried by MRSA strains disseminated in the community.     

Successful multiresistant community-associated methicillin-resistant Staphylococcus aureus lineage from Taipei, Taiwan, that carries either the novel Staphylococcal chromosome cassette mec (SCCmec) type VT or SCCmec type IV

Methicillin-resistant Staphylococcus aureus (MRSA) isolates carry the methicillin resistance gene (mecA) on a horizontally transferred genetic element called the staphylococcal chromosome cassette mec (SCCmec). Community-acquired MRSA (CAMRSA) isolates usually carry SCCmec type IV. We previously reported that 76% of 17 CAMRSA isolates (multilocus sequence type 59) obtained from pediatric patients with skin and soft tissue infections (SSTI) from Taipei did not carry SCCmec types I to IV. We used DNA sequence analysis to determine that the element harbored by these nontypeable isolates is a novel subtype of SCCmec V called SCCmec V(T.) It contains a ccrC recombinase gene variant (ccrC2) and mec complex C2. One SSTI isolate contained molecular features of SCCmec IV but also contained ccrC2 (a feature of SCCmec V(T)), suggesting that it may harbor a composite SCCmec element. The genes lukS-PV and lukF-PV encoding the Panton-Valentine leukocidin (PVL) were present in all CAMRSA SSTI isolates whether they contained SCCmec type IV or V(T). SCCmec V(T) was also present in 5 of 34 (14.7%) CAMRSA colonization isolates collected from healthy children from Taipei who lacked MRSA risk factors. Four (80%) of the these isolates contained lukS-PV and lukF-PV, as did 1 of 27 (3.7%) SCCmec IV-containing colonization isolates. A total of 63% (10 of 16) of the SSTI isolates and 61.7% (21 of 34) of the colonization isolates tested were resistant to at least four classes of non-beta-lactam antimicrobials. SCCmec V(T) is a novel SCCmec variant that is found in multiply resistant CAMRSA strains with sequence type 59 in Taipei in association with the PVL leukotoxin genes.     

A new multiplex PCR for easy screening of methicillin-resistant Staphylococcus aureus SCCmec types I–V

A multiplex PCR with four primer-pairs was designed to identify the five main known SCCmec types. A clear and easily discriminated band pattern was obtained for all five types. The SCCmec type was identified for 98% of 312 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). SCCmec type IV was by far the most common SCCmec type among both hospital- and community-acquired MRSA isolates in Denmark.     

Risk factors and molecular analysis of community methicillin-resistant Staphylococcus aureus carriage

A total of 1,838 subjects from the community and 393 subjects from health care-related facilities in Taiwan were evaluated for the prevalence of nasal Staphylococcus aureus colonization and to identify risk factors associated with S. aureus and methicillin-resistant S. aureus (MRSA) colonization. Among the community subjects, 3.5% had nasal MRSA colonization. Subjects from health care-related facilities had a lower S. aureus colonization rate (19.1%) than community subjects (25.2%) but had a significantly higher rate of colonization with MRSA (7.63%). Age (P < 0.001) was a significant risk factor for S. aureus colonization, with subjects under age 20 years or between 71 and 80 years showing higher rates of colonization. Recent gastrointestinal disease (P = 0.011) and hospital admission (P = 0.026) were risk factors for nasal MRSA colonization. Comparison of hospital MRSA isolates with the colonization strains by staphylococcal cassette chromosome mec (SCCmec) gene typing and pulsed-field gel electrophoresis (PFGE) typing revealed that most MRSA strains carried in the community were SCCmec type IV and that most clinical hospital isolates were type III, while health care facility-related carriage isolates were mainly SCCmec type III and type IV. Two new variant SCCmec types were identified. Six clusters of PFGE patterns were distinguished: two mainly comprised health care facility-related MRSA strains, three mainly comprised community MRSA strains, and one comprised mixed community and health care facility-related MRSA strains. In conclusion, a high prevalence of MRSA colonization was observed among people with no relationship to the hospital setting. The high level of multiple-drug resistance among community MRSA strains in association with the previously reported excessive use of antibiotics in Taiwan highlights the importance of the problem of antibiotic selective pressure. Our results indicate that both the clonal spread of MRSA and the transmission of hospital isolates contribute to the high MRSA burden in the community.     

Characterisation of methicillin-resistant Staphylococcus aureus isolates from dogs and their owners

Ten methicillin-resistant Staphylococcus aureus (MRSA) isolates from healthy owners and their pets were characterised by susceptibility testing, staphylococcal chromosome cassette (SCC)mec and agr typing, and detection of the Panton-Valentine leukocidin (PVL) genes. Two human and three dog isolates harbouring SCCmec type III appeared to be of hospital origin. The five remaining isolates carried SCCmec type IV, with three being multidrug-resistant. One type IV isolate was PVL-positive and a prototypic agr type 3, typified by strain MW2. This is the first report of this type in association with nasal carriage. Drug resistance may be increasing among community isolates of MRSA.     

Differences in clinical and molecular characteristics of skin and soft tissue methicillin-resistant Staphylococcus aureus isolates between two hospitals in Northern California

Community-onset methicillin-resistant Staphylococcus aureus (CO-MRSA) skin and soft tissue infections (SSTI) are associated with SCCmec IV and Panton-Valentine leukocidin (PVL) genes. CO-MRSA epidemiologic studies suggest that genotypic variation exists within one geographic region. We compared MRSA genotypes and demographic and clinical characteristics of patients with CO-MRSA SSTI between two regional medical centers. We also examined factors associated with SCCmec IV and PVL carriage. A total of 279 MRSA SSTI isolates from 2000 to 2002 at San Francisco General Hospital (SFGH) and Stanford University Hospital (SUH) were genotyped by pulsed-field gel electrophoresis and PCR for SCCmec and PVL genes. Medical records were reviewed for clinical characteristics. Ninety-three percent and 69% of MRSA SSTI were caused by CO-MRSA at SFGH and SUH, respectively. Patients with CO-MRSA SSTI at SFGH were more likely to be nonwhite, younger, homeless, and have no previous exposure to health care (P < 0.01). SFGH CO-MRSA strains were more likely to carry SCCmec type IV and PVL genes (90% and 55%, respectively) than SUH strains (29% and 16%, respectively). In multivariate analyses, nonwhite ethnicity was associated with both SCCmec type IV and PVL carriage (odds ratio [OR] of 2.65 and 95% confidence interval [CI] of 1.19 to 5.95 and OR of 1.94 and 95% CI of 1.03 to 3.65, respectively). ST8:USA300:IV became the dominant clone at SFGH, but not at SUH, by 2002. Despite geographic proximity, CO-MRSA SSTI exhibited differing SCCmec types, PVL carriage, and clonal dynamics. CO-MRSA SSTI at SUH were more likely to represent feral isolates of nosocomial origin. Clinicians should assess for nosocomial and community risk factors, realizing that different populations with CO-MRSA SSTI may require separate antimicrobial strategies.     

Molecular epidemiologic analysis of methicillin-resistant Staphylococcus aureus isolates from bacteremia and nasal colonization at 10 intensive care units: multicenter prospective study in Korea

We investigated molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) isolated at 10 intensive care units (ICUs) in Korea. MRSA isolates from bacteremia and nasal colonization were collected prospectively from October 2008 through May 2009 at 10 University-affiliated hospital ICUs. A total of 83 and 175 MRSA strains were isolated from bacteremia and nasal colonization, respectively. Acquired group accounted for 69.9% (n = 58) of bacteremia and 73.1% (n = 128) of nasal colonization. Pulsed-field gel electrophoresis (PFGE) type B (SCCmec type II/ST5) was dominant in the acquired group followed by PFGE type D (SCCmec type IVA/ST72; a community genotype). Seven of 58 (12.1%) acquired bacteremia and 15 of 128 (11.8%) acquired nasal colonizations had SCCmec type IVA/ST72 genotype, which indicated that the community genotype had already emerged as a cause of ICU acquired MRSA infection or colonization. Antibiotic resistance rates to ciprofloxacin, tetracycline, clindamycin and trimethoprim/ sulfamethoxazole were 84.4%, 67.1%, 78.1%, and 12.0%, respectively. Susceptibility to ciprofloxacin best predicted a community genotype (sensitivity 96.5%; specificity 96.9%; odds ratio 861; 95% confidence interval 169-4,390, P < 0.001) and the positive predictive value was 90.2%. Among 23 nasal re-colonized strains, 7 MRSA strains (30.4%) were different from the originally colonized strains on the basis of PFGE types.     

Dissemination of community-acquired methicillin-resistant Staphylococcus aureus clones in northern Norway: sequence types 8 and 80 predominate

Increasing frequencies of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) strain isolation have been reported from many countries. The overall prevalence of MRSA in Norway is still very low. MRSA isolates (n = 67) detected between 1995 and 2003 in northern Norway were analyzed by pulsed-field gel electrophoresis, multilocus sequence typing, and staphylococcal cassette chromosome mec (SCCmec) typing. Sixty-seven isolates were associated with 13 different sequence types. Two successful MRSA clones predominated. Sequence type 8 (ST8) (40%) and ST80 (19%) containing SCCmec type IV were detected in hospitals and communities in different geographic regions during a 7-year period. In general, there was a low level of antimicrobial resistance. Only 26% of the isolates were multiresistant. International epidemic clones were detected. The frequent findings of SCCmec type IV (91%) along with heterogeneous genetic backgrounds suggest a horizontal spread of SCCmec type IV among staphylococcal strains in parallel with the clonal spread of successful MRSA strains.     

Prevalence of methicillin-resistant Staphylococcus aureus nasal colonization among Taiwanese children in 2005 and 2006

From July 2005 to October 2006, a total of 3,046 children, of ages between 2 months and 5 years, presented for a well-child health care visit to one of three medical centers, which are located in the northern, central, and southern parts of Taiwan, and were surveyed for nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA). The overall prevalences of S. aureus and MRSA nasal carriage among the children were 23% and 7.3%, respectively (18% and 4.8% in the central region, 25% and 6.7% in the southern region, and 27% and 9.5% in the northern region). Of the 212 MRSA isolates (96%) available for analysis, a total of 10 pulsed-field gel electrophoresis (PFGE) patterns with two major patterns (C [61%] and D [28%]) were identified. One hundred forty-nine isolates (70%) contained type IV staphylococcal cassette chromosome mec (SCCmec) DNA, and 55 isolates (26%) contained SCCmec V(T). The presence of Panton-Valentine Leukocidin (PVL) genes was detected in 60 isolates (28%). Most MRSA isolates belonged to one of two major clones, characterized as sequence type 59 (ST59)/PFGE C/SCCmec IV/absence of PVL genes (59%) and ST59/PFGE D/SCCmec V(T)/presence of PVL genes (25%). We concluded that between 2005 and 2006, 7.3% of healthy Taiwanese children were colonized by MRSA in nares. MRSA harbored in healthy children indicates an accelerated spread in the community.     

Reliability of the BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) assay in detecting MRSA isolates with a variety of genotypes from the United States and Taiwan

The BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) assay is a molecular screening test for detection of MRSA in nasal colonization. This assay coamplifies the extremity of staphylococcal chromosome cassette mec (SCCmec) and adjacent chromosomal DNA at the SCCmec insertion site. Increasing reports of novel SCCmec types and the diverse genetic backgrounds of MRSA strains prompted us to test the accuracy of the BD GeneOhm MRSA kit with 914 MRSA isolates with a variety of SCCmec types harbored in 21 genetic backgrounds, as determined by the multilocus sequence type (ST). The BD GeneOhm MRSA assay was performed on colony lysates; purified genomic DNA (0.2 pg/μl and 0.2 ng/μl) was tested to confirm negative results from lysates. Of 914 MRSA isolates tested, 911 tested positive (detection rate, 99.7%). The SCCmec types carried by assay-positive isolates were I, II, III, IV, V, V(5C2&5), VI, and VIII and SCCmec composite islands with mec class A and ccr complexes 2 and 4. One of the assay-negative isolates had a community-associated genotype: ST8, SCCmec type IV. However, this was an outlier among the 99.8% (434/435) ST8, SCCmec type IV-containing isolates that tested positive. The two other assay-negative isolates had a health care-associated genotype (ST5); both carried a distinct, uncommon, composite SCCmec type. In summary, the BD GeneOhm MRSA assay had a high rate of detection of MRSA isolates harboring common and uncommon SCCmec types from the United States and Taiwan.     

Identification of staphylococcal cassette chromosome mec encoding methicillin resistance in Staphylococcus aureus isolates at Charles Nicolle Hospital of Tunis

Staphylococcal cassette chromosome is a mobile element that carries the gene mecA mediating the methicillin resistance in staphylococci. In Staphylococcus aureus five types of SCCmec have been described, which differs in size and genetic composition among strains. SCCmec typing of 34 non redundant methicillin-resistant S. aureus (MRSA) recovered in 2004 at Charles Nicolle Hospital of Tunis was carried out. The isolates were identified by conventional methods. Methicillin resistance was detected by oxacillin and cefoxitin disks and confirmed by mecA PCR. The SCCmec complex types were determined by using PCR which amplify a sequence overlapping the right SCCmec chromosome junction. Strains were recovered mainly from cutaneous pus (61.7%) and blood cultures (17.64%). They were isolated from different wards: medicine (53.1%) especially from dermatology (41.2%); surgery (40.6%) and pediatrics (3.1%). Only two strains were community-acquired MRSA. Two strains (5.9%) were harboring SCCmec type I; five (14.7%) SCCmec type II and 27 (79.4%) SCCmec type III. The two community-acquired MRSA were harboring type II and III SCCmec, usually found in hospital acquired MRSA. Our findings indicate that there are only three SCCmec types at Charles Nicolle Hospital. However, the existence of SCCmec types II and III in community incite us to investigate more community-acquired MRSA.     

Detection of diverse SCCmec variants in methicillin-resistant Staphylococcus aureus and comparison of SCCmec typing methods

Non-duplicate methicillin-resistant Staphylococcus aureus (MRSA) isolates (n = 436), collected from four hospitals located in three Korean cities between 2001 and 2005, were investigated by SCCmec typing and multilocus sequence typing (MLST). Variations within SCCmec, especially type II, were detected in 165 (37.8%) isolates, and these variants were characterised using four different SCCmec typing methods. The predominant SCCmec type was a type II variant that differed from type II by the absence of a pUB110 insertion. MLST analysis showed that most of the isolates carrying SCCmec variants belonged to ST5.     

Staphylococcus haemolyticus as an important hospital pathogen and carrier of methicillin resistance genes

Phenotypic and molecular methods were used to characterize the antibiotic resistance of 64 clinical isolates of Staphylococcus haemolyticus. By PCR of the mecA gene, 87% were found to be methicillin resistant. Approximately 55% harbored staphylococcal cassette chromosome mec element (SCCmec) type V, and only one SCCmec type IV. Many isolates (75%) displayed multiresistance, and pulsotype analysis showed a high diversity.     

Molecular pattern and antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus isolates at a teaching hospital in Northern Taiwan.

BACKGROUND AND PURPOSE: Methicillin-resistant Staphylococcus aureus (MRSA) infection has progressively increased worldwide. Knowledge of the specific epidemiological pattern of isolates at individual hospitals is important. METHODS: MRSA bacteremia was diagnosed in a total of 68 patients from January 2002 through December 2003, stratified for drug susceptibility and molecular pattern (staphylococcal cassette chromosome mec element [SCCmec] typing and genotypes). RESULTS: SCCmec-A-positive isolates were found on polymerase chain reaction in 58 patients. The most frequent SCCmec types were III (40 cases) of which less than 5% were susceptible to other beta-lactam antibiotics and most were health care-associated, followed by SCCmec type IV (15 cases), that were demonstrated to be community-acquired. SCCmec type IV MRSA isolates were more likely to be susceptible to ciprofloxacin (93.3%), gentamicin (46.7%) and trimethoprim-sulfamethoxazole (93.3%) than type III isolates. All MRSA isolates were susceptible to glycopeptides and vancomycin (minimum inhibitory concentrations <2 microg/mL). Pulsed-field gel electrophoresis with SmaI digestion was used to fingerprint these isolates. A total of 9 genotypes with 26 type-subtypes were identified. Genotype A was the most frequent (9 subtypes) indicating that it is epidemic in this hospital. CONCLUSION: After analysis, SCCmec typing could be used to predict drug susceptibility. Specific clones of S. aureus are circulating in hospital and communities in Taiwan.     

Staphylococcal cassette chromosome mec and Panton-Valentine leukocidin characterization of methicillin-resistant Staphylococcus aureus clones

Staphylococcal cassette chromosome mec (SCCmec) types and Panton-Valentine leukocidin (PVL) gene carriage were compared among suspected community-associated methicillin-resistant Staphylococcus aureus MRSA (CA-MRSA) and health care-associated MRSA (HA-MRSA) isolates. CA-MRSA isolates carried the SCCmec type IV complex, and most were PVL positive. The HA-MRSA isolates carried the SCCmec type II complex and did not harbor the PVL genes.     

Characterisation of non-multiresistant methicillin-resistant Staphylococcus aureus (including EMRSA-15) in Kuwait Hospitals

This study characterised non-multiresistant methicillin-resistant Staphylococcus aureus (nmMRSA) isolates from Kuwait hospitals to ascertain whether they were community-acquired MRSA (CA-MRSA). Forty-two nmMRSA isolates obtained between July 2001 and October 2003 were analysed by staphylococcal cassette chromosome mec (SCCmec) typing, bacteriophage typing, production of Panton-Valentine leukocidin (PVL), urease and staphylococcal enterotoxins A, B, C and D, TSST-1, and by pulsed-field gel electrophoresis (PFGE). Forty-one isolates were SCCmec type IV, and one isolate was SCCmec type III. The isolates belonged to six PFGE patterns, with two types, A and D, distributed in six and four hospitals, respectively. Most (n = 26; 61.9%) isolates produced urease. These isolates were mainly from wound and skin infections, showed low-level methicillin resistance (MIC 8-48 mg/L), and nine carried genes for PVL. These characteristics, together with their carriage of the type-IV SCCmec, identified the isolates as CA-MRSA. Ten of the 16 urease-negative isolates produced staphylococal enterotoxin C; 12 reacted weakly with phage 75, and were resistant to clindamycin and/or erythromycin, which are characteristics of EMRSA-15. Thus, this study identified the co-existence of two types of nmMRSA, i.e., CA-MRSA and EMRSA-15, in Kuwait hospitals.     

Clonal spread of SCCmec type IV methicillin-resistant Staphylococcus aureus between community and hospital

The staphylococcal chromosome cassette (SCC)mec types of 382 hospital-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA) isolates in Taiwan were analysed over a 7-year period (1999-2005). There was an abrupt increase in SCCmec type IV in HA-MRSA during 2005. The molecular epidemiology of a subset (n = 69) of HA-MRSA isolates with SCCmec types III, IV or V was characterised and compared with that of community-acquired MRSA (CA-MRSA) (n = 26, collected during 2005). Pulsed-field gel electrophoresis revealed three major pulsotypes (A, B and C) and 15 minor clones. Pulsotypes B and C, which contained isolates carrying SCCmec types IV and V, respectively, included both CA-MRSA and HA-MRSA isolates. Among 24 toxin genes analysed, five genes had significant differential distribution between CA-MRSA and SCCmec type III HA-MRSA. Furthermore, among SCCmec type IV isolates, the seb gene was detected more commonly in HA-MRSA. Analysis of representative members of the three major pulsotypes by multilocus sequence typing revealed two sequence types (STs), namely ST239 (SCCmecIII) and ST59 (SCCmecIV or SCCmecV). This suggests that ST59:SCCmecIV, which is usually community-acquired, has become an important nosocomial pathogen in the hospital studied.     

The emergence and importation of diverse genotypes of methicillin-resistant Staphylococcus aureus (MRSA) harboring the Panton-Valentine leukocidin gene (pvl) reveal that pvl is a poor marker for community-acquired MRSA strains in Ireland

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) carrying pvl is an emerging problem worldwide. CA-MRSA tends to harbor staphylococcal cassette chromosome mec type IV (SCCmec IV), to be non-multiantibiotic resistant, and to have different genotypes from the local hospital-acquired MRSA (HA-MRSA). However, in Ireland, 80% of HA-MRSA isolates have the non-multiantibiotic-resistant genotype ST22-MRSA-IV. This study investigated MRSA isolates from Ireland (CA-MRSA, health care-associated MRSA, and HA-MRSA) for the carriage of pvl and determined the genotypic characteristics of all pvl-positive isolates identified. All 1,389 MRSA isolates were investigated by antibiogram-resistogram typing and SmaI DNA macrorestriction analysis. pvl-positive isolates were further characterized by multilocus sequence typing and SCCmec, agr, and toxin gene typing. Twenty-five (1.8%) MRSA isolates belonging to six genotypes (ST30, ST8, ST22, ST80, ST5, and ST154) harbored pvl. Nineteen of these (76%) were CA-MRSA isolates, but a prospective study of MRSA isolates from 401 patients showed that only 6.7% (2/30) of patients with CA-MRSA yielded pvl-positive isolates. Thus, pvl cannot be used as a sole marker for CA-MRSA. Fifty-two percent of pvl-positive MRSA isolates were recovered from patients with skin and soft tissue infections; thirty-six percent were from patients of non-Irish ethnic origin, reflecting the increasing heterogeneity of the Irish population due to immigration. All 25 pvl-positive isolates carried SCCmec IV; 14 (56%) harbored SCCmec IV.1 or IV.3, and the remaining 11 isolates could not be subtyped. This study demonstrates that pvl is not a reliable marker for CA-MRSA in Ireland and reveals the emergence and importation of diverse genotypes of pvl-positive MRSA in Ireland.