Distribution of major genotypes among methicillin-resistant Staphylococcus aureus clones in Asian countries

To investigate the evolutionary pattern and genotypic characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains in the Asian region, 74 MRSA strains isolated from 12 Asian countries were analyzed by multilocus sequence typing (MLST) and SCCmec typing. Overall, a total of 16 genotypes based on sequence type and SCCmec types were identified among MRSA strains from Asian countries. Data revealed two major genotypes of MRSA strains in Asia, with unique geographic distributions. By MLST analysis, all strains from Korea and Japan except one belonged to clonal complex 5 (CC5) while most MRSA isolates from other Asian countries belonged to CC239. SCCmec typing showed that most isolates from Korea and Japan were SSmec type II whereas SCCmec type III (or IIIA) was the most common type in strains from other Asian countries. Our data documented a unique geographic distribution and evolutionary pattern of MRSA clones in Asia.     

Contemporary methicillin-resistant Staphylococcus aureus clones in Hong Kong

Two hundred non-duplicate methicillin-resistant Staphylococcus aureus (MRSA) isolates causing bacteremia in patients in four major Hong Kong hospitals during the period 2000 to 2001 were characterized by antibiogram, pulsed-field gel electrophoresis (PFGE) using SmaI restriction enzymes, and determination of staphylococcal cassette chromosome mec (SCCmec) types. Nine PFGE types, A to I, were obtained. PFGE type A constituted 50% (99/200) of all isolates and was present in isolates from all four hospitals. PFGE types A to E, had previously been identified as the major types at one of the hospitals from 1988 to 2000. The majority had a resistance profile to tetracycline (T), erythromycin (E), clindamycin (D), gentamicin (G), tobramycin (To), and ciprofloxacin (Ci), and belonged to SCCmec type III; and representatives belonged to clonal complex 239 (CC 239) (MRSA with SCCmec type III and sequence type 239, designated ST 239-MRSA-III). PFGE types F to I were new patterns that had not been previously identified in isolates from Hong Kong. PFGE type F constituted 18% (35/200) of MRSAs, had resistance profile TEGToCi, and belonged to CC 5 (ST 5-MRSA-II). PFGE type G included 13% (26/200) of MRSAs, had resistance profile TECi, and belonged to CC 45 with SCCmec type I or II. PFGE type H had characteristics similar to those of CC 239, while PFGE type I included three isolates, two of which expressed resistance to oxacillin and fusidic acid only. Two of these strains had SCCmec IVa and carried sequence type 389, with a multilocus sequence typing allelic profile of 3-35-19-2-20-26-39. Contemporary MRSAs causing bacteremia in Hong Kong hospitals belong to three clonal complexes (CC 5, CC 45, and CC 239). The most prevalent MRSA clone in Hong Kong belongs to CC 239, with PFGE types A to E and H, SCCmec type III, ST 239, and a resistance profile of TEDGToCi.     

Molecular epidemiology of community-associated antimicrobial-resistant Staphylococcus aureus in Seoul, Korea (2003): pervasiveness of multidrug-resistant SCCmec type II methicillin-resistant S. aureus

There is an extremely high incidence of antimicrobial resistance of the clinical isolates of Staphylococcus aureus in Korea. This study carried out a molecular investigation to determine the prevalence of the community-associated antimicrobial-resistant S. aureus and methicillin-resistant S. aureus (MRSA). The percentage resistance from the nasal swabs of healthy volunteers in 2003 in Seoul is as follows: penicillin (91%), erythromycin (EM, 14%), gentamicin (GM, 9.3%), tetracycline (TE, 8.2%), cephalothin (4%), oxacillin (OX, MRSA; 3.8%), clindamycin (CC, 2.6%), ciprofloxacin (CIP, 0.8%), and sulfamethoxazole/trimethoprim (0.6%). The community-associated MRSA (C-MRSA) strains were examined by pulsed-field gel electrophoresis (PFGE) analysis of the SmaI macro-fragments, multilocus sequence typing (MLST), and staphylococcal cassette chromosome mec (SCCmec) typing using the PCR analysis. The Korean C-MRSA isolates were clustered into three distinct groups. One PFGE group containing the C-MRSA strains showed resistance to CC, EM, and GM, a high level (32-96 microg/ml) of resistance to methicillin, sequence type 5 (ST5), and SCCmec type II, which is the most common hospital associated-MRSA (H-MRSA) isolated in Korea. These results highlight the heterogeneous genetic background of the C-MRSA as well as the pervasiveness of the H-MRSA isolates in this community.     

Genetic diversity among community methicillin-resistant Staphylococcus aureus strains causing outpatient infections in Australia

Increasing reports of the appearance of novel nonmultiresistant methicillin-resistant Staphylococcus aureus MRSA (MRSA) strains in the community and of the spread of hospital MRSA strains into the community are cause for public health concern. We conducted two national surveys of unique isolates of S. aureus from clinical specimens collected from nonhospitalized patients commencing in 2000 and 2002, respectively. A total of 11.7% of 2,498 isolates from 2000 and 15.4% of 2,486 isolates from 2002 were MRSA. Approximately 54% of the MRSA isolates were nonmultiresistant (resistant to less than three of nine antibiotics) in both surveys. The majority of multiresistant MRSA isolates in both surveys belonged to two strains (strains AUS-2 and AUS-3), as determined by pulsed-field gel electrophoresis (PFGE) and resistogram typing. The 3 AUS-2 isolates and 10 of the 11 AUS-3 isolates selected for multilocus sequence typing (MLST) and staphylococcal chromosomal cassette mec (SCCmec) analysis were ST239-MRSA-III (where ST is the sequence type) and thus belonged to the same clone as the eastern Australian MRSA strain of the 1980s, which spread internationally. Four predominant clones of novel nonmultiresistant MRSA were identified by PFGE, MLST, and SCCmec analysis: ST22-MRSA-IV (strain EMRSA-15), ST1-MRSA-IV (strain WA-1), ST30-MRSA-IV (strain SWP), and ST93-MRSA-IV (strain Queensland). The last three clones are associated with community acquisition. A total of 14 STs were identified in the surveys, including six unique clones of novel nonmultiresistant MRSA, namely, STs 73, 93, 129, 75, and 80slv and a new ST. SCCmec types IV and V were present in diverse genetic backgrounds. These findings provide support for the acquisition of SCCmec by multiple lineages of S. aureus. They also confirm that both hospital and community strains of MRSA are now common in nonhospitalized patients throughout Australia.     

Methicillin-resistant Staphylococcus aureus in hospitals in Tbilisi, the Republic of Georgia, are variants of the Brazilian clone

The purpose of this study was to characterise methicillin-resistant Staphylococcus aureus (MRSA) isolates from the Republic of Georgia, part of the former Soviet Union. Thirty-two non-duplicate MRSA isolates were collected in the period from May 2006 to February 2007. The patient data were analysed and the isolates were characterised by staphylococcal protein A (spa) typing, staphylococcal chromosome cassette mec (SCCmec) typing, multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE) and the detection of Panton-Valentine leukocidin (PVL) genes. Only two closely related spa types were found; 29 isolates were of spa type 459 and three were t030. The spa types belonged to sequence type (ST) 239, clonal complex (CC) 8. All isolates were multiresistant, PVL-negative and harboured SCCmec type IIIA. Based on the molecular findings and PFGE, the isolates most closely resembled the pandemic Brazilian clone (ST239-IIIA).     

Prevalence of the ST239 clone of methicillin-resistant Staphylococcus aureus and differences in antimicrobial susceptibilities of ST239 and ST5 clones identified in a Korean hospital

A total of 188 nonduplicate methicillin-resistant Staphylococcus aureus (MRSA) isolates obtained between 2001 and 2004 in a university hospital in Daegu, Korea, were analyzed for their clonal types by molecular typing techniques, including multilocus sequence typing, spaA typing, staphylococcal chromosomal cassette mec (SCCmec) typing, and pulsed-field gel electrophoresis (PFGE). They were examined for their antimicrobial susceptibilities. The majority (87%) of MRSA isolates belonged to sequence type 239 (ST239; n = 100; 53%) and ST5 (n = 63, 34%) on the basis of sequence typing. MRSA isolates belonging to ST239 were genotypically homogeneous, while those belonging to ST5 showed variations in spaA type, SCCmec type, and PFGE patterns. The rates of resistance of the MRSA isolates belonging to ST239 to trimethoprim, sulfamethoxazole, tobramycin, gentamicin, erythromycin, and tetracycline were significantly higher than those of the isolates belonging to ST5 (P < 0.05). This study demonstrated that the ST239 clone, while rarely detected in Korea, was prevalent and that the antimicrobial susceptibility of the ST239 clone was significantly different from that of the ST5 clone.     

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.     

Clonal composition of Staphylococcus aureus isolates at a Brazilian university hospital: identification of international circulating lineages

In only a few instances has the clonal composition of Staphylococcus aureus collections that include methicillin-susceptible S. aureus (MSSA) been extensively characterized. In order to investigate the clonal composition of MSSA and methicillin-resistant S. aureus (MRSA) and examine whether the infections diagnosed at our hospital were related to internationally distributed S. aureus lineages, we collected 89 clinical S. aureus isolates from patients at a public university hospital in Rio de Janeiro, Brazil, from September 1999 to June 2000. All S. aureus isolates were genotyped by pulsed-field gel electrophoresis and multilocus restriction fragment typing (MLRFT), and a subset (n = 17) was further characterized by multilocus sequence typing (MLST). The 34 MRSA isolates were additionally characterized by SCCmec typing. The MSSA population (n = 55) was grouped into 18 restriction fragment types (RFTs); of these, five RFTs accounted for 67% (37) of the MSSA isolates. MRSA isolates were clustered into only three RFTs (P = 0.02). The majority of MSSA RFTs were related to sequence type 30 (ST30) (12 isolates, 22%), ST1, ST188, and ST432 (6 isolates, 11% each). The predominant MRSA RFT comprised 31 (91%) of 34 isolates; four randomly selected isolates of this RFT were ST239, the previously described widely disseminated Brazilian clone. However, a fifth isolate belonging to this RFT was the ST644, a new single locus variant of ST239. By applying MLRFT and MLST, we found evidence for a clonal structure in MSSA isolates and detected the dissemination of MSSA clonal complexes 1, 5, 8, 30, and 45.     

Clinical isolates of Staphylococcus aureus from the Arkhangelsk region,Russia: antimicrobial susceptibility,molecular epidemiology,and distribution of Panton‐Valentine leucocidin genes

A total of 91 consecutive clinical isolates of Staphylococcus aureus were collected at the Regional Hospital of Arkhangelsk, Russia, from May to December 2004, and examined for antimicrobial susceptibility, methicillin resistance and presence of Panton‐Valentine leucocidin (PVL) genes. Epidemiological typing was performed by pulsed‐field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Methicillin‐resistant S. aureus (MRSA) isolates were examined by staphylococcal cassette chromosome mec (SCCmec) typing. High‐to‐moderate rates of resistance to penicillin (β‐lactamase production; 93%), tetracycline (40%), erythromycin and clindamycin (32%) were observed. Forty out of ninety‐one (44%) isolates were positive for PVL genes. Thirty‐six (40%) PVL‐positive methicillin‐susceptible S. aureus (MSSA) strains were shown by PFGE and MLST typing (ST121, ST681, ST837) to be part of a nosocomial outbreak caused by clonal complex (CC) 121. PFGE, MLST and SCCmec typing revealed three MRSA clones. Sequence type (ST) 239‐III (n=11), ST1097‐III (n=1) and ST8‐IV (n=3) belong to CC8 of epidemic multiresistant MRSA, whereas ST426‐MRSA‐IV/CC395 (n=1) has not been reported previously. All MRSA strains were PVL negative. The overall results underline the necessity of microbiological sampling, antimicrobial susceptibility testing, and epidemiological typing as a rational basis for antimicrobial treatment of S. aureus infections, and infection control measures to limit the spread of multiresistant MRSA and epidemic MSSA clones.     

Evolution and molecular characterization of methicillin-resistant Staphylococcus aureus epidemic and sporadic clones in Cordoba, Argentina

Since 1999, a new, epidemic, methicillin-resistant Staphylococcus aureus (MRSA) strain, named the "Cordobes clone," has emerged in Argentina and coexists with the pandemic Brazilian clone. The purpose of this study was to determine the stability over time of the new clone and to investigate its evolutionary relationship with epidemic international MRSA lineages and with other MRSA and methicillin-susceptible S. aureus (MSSA) major clones distributed in this region. One hundred three MRSA isolates recovered in 2001 from Cordoba, Argentina, hospitals and 31 MSSA strains collected from 1999 to 2002 were analyzed by their antibiotic resistance patterns, phage typing, and pulsed-field gel electrophoresis. Additionally, representative members of most MRSA defined genotypes (A, B, C, E, K, and I) were characterized by multilocus sequence typing (MLST) and spaA and SCCmec typing. The most prevalent MSSA pulsotypes were also analyzed by MLST. Our results support the displacement of the Brazilian clone (sequence type [ST] 239, spaA type WGKAOMQ, SCCmec type IIIA) by the Cordobes clone (ST5, spaA type TIMEMDMGMGMK, SCCmec type I) in the hospital environment. MRSA and MSSA isolates shared only ST5. The data support the origin of the Cordobes clone as a member of a lineage that includes the pediatric and New York/Japan international clones and that is genetically related to the British EMRSA-3 strain. Interestingly, the pediatric clone, isolated from most community-acquired infections in Cordoba, was characterized by ST100, a single-locus variant of ST5 and a new variant of SCCmec type related to SCCmec type IVc.     

Frequent recovery of a single clonal type of multidrug-resistant Staphylococcus aureus from patients in two hospitals in Taiwan and China

One hundred thirty-two methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered from patients with S. aureus infections between January 1998 and February 1999 in two hospitals, one located in Taipei, Taiwan, and another in Nanjing, People's Republic of China, were examined for antibiotic susceptibility and for clonal type by a combination of three methods: hybridization of ClaI restriction digests with mecA- and Tn554-specific DNA probes and pulsed-field gel electrophoresis of chromosomal SmaI digests. Selected isolates representing each clonal type were also analyzed by spaA typing, multilocus sequence typing, and a multiplex PCR method capable of identifying the structural type of the staphylococcal cassette chromosome mec (SCCmec) carried by the bacteria. The overwhelming majority of isolates (126 of 132 or 95%) belonged to minor variants of a single clonal type resembling the Brazilian and Hungarian epidemic MRSA clones, which showed a common spaA type and which were either sequence type 239 (ST239) or ST241 (a single-locus variant of ST239) in association with SCCmec type III or IIIA.     

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.     

Characterization of Methicillin-Resistant Staphylococcus aureus Strains Recovered from a Phase IV Clinical Trial for Linezolid versus Vancomycin for Treatment of Nosocomial Pneumonia

A total of 434 methicillin-resistant Staphylococcus aureus (MRSA) baseline isolates were collected from subjects enrolled in a prospective, double-blind randomized trial comparing linezolid versus vancomycin for the treatment of nosocomial pneumonia. Isolates were susceptibility tested by broth microdilution, examined for inducible clindamycin resistance by D-test, and screened for heterogeneous resistance to vancomycin (hVISA) by the Etest macromethod. All strains were subjected to Panton-Valentine leukocidin (PVL) screening, and SCCmec, pulsed-field gel electrophoresis (PFGE), and spa typing. Selected strains were evaluated by multilocus sequence typing (MLST). Clonal complexes (CCs) were assigned based on the spa and/or MLST results. Most strains were CC5 (56.0%), which originated from North America (United States) (CC5-MRSA-SCCmec II/IV; 70.0%), Asia (CC5-MRSA-II; 14.0%) and Latin America (CC5-MRSA-I/II; 12.3%). The second- and third-most-prevalent clones were CC8-MRSA-IV (23.3%) and CC239-MRSA-III (11.3%), respectively. Furthermore, the CC5-MRSA-I/II clone predominated in Asia (50.7% within this region) and Latin America (66.7%), followed by CC239-MRSA-III (32.8% and 28.9%, respectively). The European strains were CC8-MRSA-IV (34.5%), CC22-MRSA-IV (18.2%), or CC5-MRSA-I/II/IV (16.4%), while the U.S. MRSA isolates were CC5-MRSA-II/IV (64.4%) or CC8-MRSA-IV (28.8%). Among the U.S. CC8-MRSA-II/IV strains, 73.7% (56/76 [21.2% of all U.S. MRSA strains]) clustered within USA300. One strain from the United States (USA800) was intermediate to vancomycin (MIC, 4 μg/ml). All remaining strains were susceptible to linezolid, daptomycin, vancomycin, and teicoplanin. hVISA strains (14.5%) were predominantly CC5-MRSA-II, from South Korea, and belonged to a single PFGE type. Overall, each region had two predominant clones. The USA300 rate corroborates previous reports describing increased prevalence of USA300 strains causing invasive infections. The prevalence of hVISA was elevated in Asia, and these strains were associated with CC5.     

Clonality of epidemic methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> strains in Finland as defined by several molecular methods

In Finland, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) strains has increased ten fold within the last decade. In order to follow the changing epidemiology of MRSA, accurate typing of S. aureus strains is important. The purpose of this study was to reanalyse 44 previously recognised Finnish epidemic MRSA strains (EMRSA) by several molecular typing methods and to revise their nomenclature. The 44 EMRSA strains were grouped into 26 pulsed-field gel electrophoresis (PFGE) clusters, 20 multi locus sequence typing (MLST) sequence types (ST) belonging to 12 clonal complexes (CC) of which CC8 was the most prevalent, and 27 spa types belonging to four clonal complexes. The staphylococcal cassette chromosome mec (SCCmec) type IV was predominant, and 48% of the strains were nonmultiresistant to antibiotics. The discriminatory power of PFGE clusters, MLST, and spa typing was high. The overall concordance values of typing methods differed when assessed by two different methods. Adjusted Rand coefficient provided fairly low correlations for all comparisons. However, spa type was able to efficiently predict types and clonal complexes of most of the other methods with high probability (>/=80%).     

A novel multiplex PCR for molecular characterization of methicillin resistant Staphylococcus aureus recovered from Jeddah, Kingdom of Saudi Arabia

Background: Molecular characterization of staphylococcal cassette chromosome mec (SCCmec) types of methicillin-resistant Staphylococcus aureus (MRSA) is very essential for studying the epidemiology of MRSA. Objectives: This study reports two multiplex PCR for molecular typing of MRSA collected from Jeddah, Kingdom of Saudi Arabia. Materials and Methods: A total of 101 clinical isolates of strains were collected from major hospital laboratories and public health centres, Jeddah, Kingdom of Saudi Arabia during the period from August 2009 to May 2011. All the strains were tested phenotypically by conventional methods and genotypically by a novel multiplex PCR targeting at the same time S. aureus 16S rRNA, Panton - valentine leucocidin (PVL) and mecA resistance genes. All the strains were tested also by multiplex PCR for typing of SCC mec types. Results: All the 101 strains previously identified phenotypically as S. aureus with bacteriological examination were positive for amplification of 756 base pair fragments specific for 16S rRNA of S. aureus. Moreover, all the strains were positive for amplification of 1339 base pair fragments specific for mecA gene, while only 38 strains (37.6%) showed positive amplification of 433 base pair fragments specific for PVL gene. The most predominant SCC mec type among the examined isolates is type V 43 (42.5) followed by SCCmec type III 39 (38.6%). Conclusion: The newly modified multiplex PCR is rapid and sensitive method for detection of MRSA. Moreover, the most predominant SCC mec type among the examined isolates from Jeddah, King Saudi Arabia is type V (42.5%), followed by Type III (38.6%).     

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.     

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.     

Molecular epidemiological analysis of methicillin-resistant Staphylococcus aureus isolates from Chinese pediatric patients

To investigate the molecular epidemiological analysis of methicillin-resistant Staphylococcus aureus (MRSA) isolates from five pediatric hospitals in China. Seventy-three MRSA isolates were analyzed by a combination of different genotyping methods, including multilocus sequence typing (MLST), SCCmec and spa typing. Panton-Valentine Leukocin (PVL) gene was also detected. The prevalent strains were ST239-MRSA-III and ST1-MRSA clones in the northern region; ST239-MRSA-III, ST910-MRSA-IV and ST88-MRSA in the eastern region; and ST59-MRSA in the southern region. Only the ST910-MRSA-IV clone has been found in China until now, and it is closely related to ST30-MRSA-IV. All MRSA isolates were found to be resistant to penicillin and azithromycin, and multidrug resistance was observed. The cases of necrotic pneumonia, severe skin and subcutaneous tissue infection and lymphadenitis resulted from PVL gene-positive MRSA. There were several novel genetic types of MRSA. Antimicrobial susceptibility tests showed high resistance of many antimicrobials and multiple drugs.     

The evolution of pandemic clones of methicillin-resistant Staphylococcus aureus: identification of two ancestral genetic backgrounds and the associated mec elements

Previous surveillance studies carried out by our laboratories, primarily in Southern and Eastern Europe, Latin America, and the United States, have characterized 3,067 methicillin-resistant Staphylococcus aureus (MRSA) hospital isolates by a combination of molecular typing methods. Nearly 70% of these isolates could be classified into five clonal types showing extensive geographic spread. Representative isolates of these clonal types were now reexamined for their genetic relatedness by multilocus sequence typing (MLST) and by sequencing the polymorphic region of protein A (spaA typing), and also for the type of the Staphylococcal Chromosomal Cassette (SCCmec) resident in the bacteria. Three of the previously classified clonal types (Iberian, Brazilian, and Hungarian clones) shared a common or closely related genetic background A, which was the same as the background of the earliest European isolates of MRSA from England and Denmark. The Pediatric and New York/Japan clones belonged to a completely different genetic background B. The three recently described SCCmec types were specifically associated with different pandemic clones: types I and III with isolates of genetic background A and type II with isolates of genetic background B. A novel SCCmec related to type I, called SCCmec type IV, was identified in some MRSA strains belonging to genetic background A as well as B. Structural variations in SCCmec types I and III were also observed. The data allow tentative identification of an evolutionary pathway for the emergence of pandemic MRSA clones and also provide evidence for the multiple, yet restricted, numbers of acquisition of the mec element by S. aureus.     

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.