Clonal and antibiotic resistance profiles of methicillin-resistant Staphylococcus aureus (MRSA) from a Portuguese hospital over time

Methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered from a general hospital in Oporto, Portugal, during two periods (1992-1993 and 1996-2000) were characterized by pulsed-field gel electrophoresis (PFGE) of SmaI fragments, and by hybridization of ClaI digests with mecA and Tn554 probes, discriminating the isolates in mecA::Tn554::PFGE genotypes. In addition, a representative sample of the defined genotypes was characterized by multilocus sequence typing (MLST) and SCCmec (staphylococcal cassette chromosome mec) typing, generating the corresponding ST-SCCmec types. In 1992-1993, 77% of MRSA belonged to the Iberian clone (genotype I::E::A or ST247-IA). In 1996-2000, the frequency of this clone decreased to 19% and the majority (69%) of the isolates belonged to another international clone, the Brazilian MRSA (genotype XI::B::B or ST239-IIIA). Trimethoprim/sulfamethoxazole (SXT) was confirmed to be an important phenotypic marker to distinguish the Iberian (SXT-susceptible) and the Brazilian (SXT-resistant) clones in MRSA isolates from Portugal. Our observations document major shifts in the dominant MRSA clonal types that occurred in this hospital since 1992, suggesting a selective advantage of the Brazilian relatively to the Iberian clone. In addition to these two MRSA clones that are the most frequent in Portuguese hospitals since the early 1990s, sporadic MRSA clones (representing 14% of the total) were identified and characterized.     

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.     

Phenotypic and genetic characterisation of methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> strains isolated from the university hospitals of Debrecen

The purpose of this study was to characterise methicillin-resistant Staphylococcus aureus (MRSA) strains isolated in 2005 at the university hospitals of Debrecen, Hungary. Three hundred and thirty-nine MRSA strains were isolated from 102 patients at 18 different clinics. Their sensitivity to oxacillin and ten other antibiotics was determined. For genotypic analysis, phage typing and pulsed-field gel electrophoresis (PFGE) was performed. The rate of MRSA strains increased to 7.2% in 2005, especially at the clinics of surgery, pulmonology and paediatrics. No vancomycin- or teicoplanin-resistant strains were found. The resistance to erythromycin, clindamycin and ciprofloxacin was nearly 100% and multi-resistance was very frequent. Fifty-eight percent of the isolates belonged to mixed phage types and 8% was non-typable. One PFGE clone contained 58.2% of all strains and two further major clones were found at a separately located clinical block, indicating intra-hospital spread. We can conclude that MRSA exhibits an increasing nosocomial problem also in Hungary. Zsuzsa Dombrádi contributed equally to the first authorship.     

Fluorescent amplified fragment length polymorphism genotyping of Salmonella Enteritidis: a method suitable for rapid outbreak recognition

Objective   To perform fluorescent amplified fragment length polymorphism (FAFLP) analysis on phage type (PT) reference strains of Salmonella enterica subsp. enterica serotype Enteritidis ( S. Enteritidis), and S . Enteritidis PT 6 and 6a recent clinical isolates to determine its usefulness for primary characterization of clinical S. Enteritidis isolates, and then to determine whether FAFLP is suitable for rapid characterization of strains in an outbreak situation.
Methods   Twenty-five PT reference strains of S. Enteritidis and 20  S . Enteritidis PT 6 and 6a clinical isolates were subjected to FAFLP analysis using the selective primer combinations Eco  + 0– Mse  + T and Eco  + 0– Mse  + TA.
Results   FAFLP successfully separated each one of the 25 S . Enteritidis PT strains into distinct profiles, while macrorestriction and PFGE using Xba I identified 20 pulsed-field profiles. FAFLP also resolved cases and outbreaks due to S . Enteritidis PTs 6 and 6a.
Conclusions   The resolving power of FAFLP was higher than that of PFGE. FAFLP is a highly discriminatory genotyping method and, in conjunction with phage typing for primary subdivision of S . Enteritidis, provides a rapid and powerful tool for strain differentiation, both for outbreak investigation and for epidemiologic surveillance.     

Epidemiology of methicillin-resistant Staphylococcus aureus in Southern Stockholm, 2000-2003

The number of patients infected/colonised by methicillin-resistant Staphylococcus aureus (MRSA) began to rise in southern Stockholm in 2000. The present study is an analysis based on information concerning the 181 newly detected patients with MRSA during 2000-2003, results of antibiotic susceptibility tests, molecular epidemiologic typing with pulsed-field gel electrophoresis and multilocus sequence typing, and detection of Panton-Valentine leukocidin genes. No single MRSA clone was causing the epidemic situation. Instead a number of rather small, limited outbreaks took place, caused by different MRSA clones and often starting from a patient who had acquired MRSA abroad. Different clones were found in the hospitals and in the community. Sequence types (STs) 22, 239, 247, 8, and 45 were the predominant clones causing outbreaks among hospitalized patients. Most isolates belonging to these clones were multiply resistant to antimicrobial agents. Suspected glycopeptide heteroresistance was found in isolates belonging to STs 247, 239, and 592. In the community, the most widely spread MRSA was ST 80, although isolates belonging to STs 8, 30, 59, and 150 were also observed. The community-acquired isolates were usually not multiresistant. In contrast to the clones transmitted in hospitals, most community-acquired MRSA clones harbored the PVL genes, except for isolates belonging to ST 150 spread in the community among homeless people with foot ulcers and wounds.     

Molecular epidemiology of methicillin-resistant Staphylococcus aureus in Spain: a multicentre prevalence study (2002)

A point-prevalence study, performed in 2002 in 143 Spanish hospitals, collected 439 isolates of Staphylococcus aureus. Of these, 134 (30.5%) were resistant to methicillin (i.e., MRSA). Susceptibility testing was performed by a microdilution method, and mecA was detected by PCR. The isolates were characterised by phage typing, pulsed-field gel electrophoresis (PFGE) after SmaI digestion, and SCCmec typing. The 134 MRSA isolates showed resistance to ciprofloxacin (93.3%), tobramycin (88.8%), erythromycin (67.9%), clindamycin (59.7%), gentamicin (42.5%), mupirocin (17.9%), rifampicin (5.2%) and trimethoprim-sulphamethoxazole (5.2%). All of the isolates were susceptible to glycopeptides. Twenty-five resistance patterns were found, of which four accounted for 66% of the isolates. Phage group III was the most frequent (41.1%). PFGE revealed 31 different patterns, with ten major clones (including two predominant clones with variable antibiotypes that accounted for 43.3% of the MRSA isolates) and 21 sporadic patterns. Two isolates belonged to two variants of the Iberian clone (ST247-MRSA-I), one to the Brazilian clone (ST239-MRSA-III), and seven to the EMRSA-16 clone (ST36-MRSA-II). SCCmecIV accounted for 70.2% of the isolates (73.9% were type IVA), while SCCmecI, SCCmecII and SCCmecIII accounted for 22.1%, 6.9% and 0.8% of isolates, respectively, with three non-typeable isolates. Isolates of SCCmecIV and SCCmecIVA were predominantly nosocomial (95.8% and 97.1%, respectively). None of the isolates produced Panton-Valentine leukocidin. Thus, two clones carrying SCCmecIV and SCCmecIVA, respectively, were predominant among nosocomial MRSA isolates throughout Spain.     

Genotyping of European isolates of methicillin-resistant Staphylococcus aureus by fluorescent amplified-fragment length polymorphism analysis (FAFLP) and pulsed-field gel electrophoresis (PFGE) typing.

A representative panel of 50 European MRSA isolates was subjected to genotype analysis by fluorescent amplified-fragment length polymorphism (FAFLP) and by macrorestriction pulsed-field gel electrophoresis (PFGE). Each isolate had a unique profile with FAFLP. To model genetic relationships within the continuing MRSA epidemic, cluster analysis of FAFLP data was made, revealing nine clone complexes of MRSA. Most of these were also found by PFGE. A number of isolates had FAFLP profiles significantly different from others, and might represent emerging epidemic strains. FAFLP analysis proved particularly suitable for surveillance of the MRSA epidemic at national and international levels.     

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 typing and epidemiological study of Salmonella enterica serotype Typhimurium isolates from cattle by fluorescent amplified-fragment length polymorphism fingerprinting and pulsed-field gel electrophoresis

One hundred twenty Salmonella enterica serotype Typhimurium strains, including 103 isolates from cattle gathered between 1977 and 1999 in the prefecture located on the northern-most island of Japan, were analyzed by using fluorescent amplified-fragment length polymorphism (FAFLP) and pulsed-field gel electrophoresis (PFGE) to examine the genotypic basis of the epidemic. Among these strains, there were 17 FAFLP profiles that formed four distinct clusters (A, B, C, and D). Isolates that belonged to cluster A have become increasingly common since 1992 with the increase of bovine salmonellosis caused by serotype Typhimurium. PFGE resolved 25 banding patterns that formed three distinct clusters (I, II, and III). All the isolates that belonged to FAFLP cluster A, in which all the strains of definitive phage type 104 examined were included, were grouped into PFGE cluster I. Taken together, these results indicate that clonal exchange of serotype Typhimurium has taken place since 1992, and they show a remarkable degree of homogeneity at a molecular level among contemporary isolates from cattle in this region. Moreover, we have sequenced two kinds of FAFLP markers, 142-bp and 132-bp fragments, which were identified as a polymorphic marker of strains that belonged to clusters A and C, respectively. The sequence of the 142-bp fragment shows homology with a segment of P22 phage, and that of the 132-bp fragment shows homology with a segment of traG, which is an F plasmid conjugation gene. FAFLP is apparently as well suited for epidemiological typing of serotype Typhimurium as is PFGE, and FAFLP can provide a source of molecular markers useful for studies of genetic variation in natural populations of serotype Typhimurium.     

Spread of old and new clones of epidemic methicillin-resistant Staphylococcus aureus in Poland

Objective: To study the relatedness among methicillin-resistant Staphylococcus aureus (MRSA) isolates originating from two regions of Poland using different epidemiologic typing methods.
Methods: Forty-five MRSA isolates (19 from Warsaw and 26 from the Grajewo region) were collected between 1995 and 1996. For phenotypic epidemiologic analysis, antimicrobial susceptibility testing (AST) with a panel of 19 antibiotics was performed. For genotypic epidemiologic analysis, pulsed-field gel electrophoresis (PFGE) of Smal-digested chromosomal DNA, restriction endonuclease analysis of plasmid (REAP) DNA digested by Hin dIII, random amplification of polymorphic DNA (RAPD) and binary typing (BT) of genomic DNA by hybridization with five different RAPD-generated strain-specific DNA probes, were used.
Results: Six clusters of clonally related strains were found among the MRSA isolates analyzed. Three of these, identified in both regions, were related to previously described Polish epidemic clones, designated HeEMRSA-Pol1 (heterogeneously methicillin resistant—18 isolates) and HoEMRSA-Pol1 (homogeneously resistant—two clones, six isolates each). The remaining three clones, identified in the Grajewo region only, are previously undescribed. One of these, represented by 11 isolates, appears to be new epidemic heterogeneous MRSA clone (HeEMRSA-Pol2). Results of PFGE and BT in general showed good correlation, and, in some cases, RAPD using AP1 and AP7 primers could discriminate between isolates belonging to single PFGE or BT types. Broad AST and REAP can provide useful additional information concerning relatedness.
Conclusion: Evidence for the spread of previously recognized epidemic MRSA clones in Poland and the presence of a new epidemic heterogeneously resistant clone of MRSA in hospitals outside Warsaw is documented.     

Epidemiology of emerging methicillin-resistant Staphylococcus aureus (MRSA) in Denmark: a nationwide study in a country with low prevalence of MRSA infection

Strict infection control measures introduced during the 1970s have kept the incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections extremely low in Denmark. Nevertheless, similarly to other countries, MRSA infections began to appear in the community in the late 1990s. A nationwide surveillance program has collected and stored all MRSA isolates since 1988 and, since 1999, clinical information has been also recorded. We used this information and isolates in a detailed epidemiological and molecular analysis of the 81 MRSA infections identified in Denmark in 2001. MRSA isolates were characterized by pulsed-field gel electrophoresis (PFGE), spa typing, multilocus sequence typing, and SCCmec typing. Comparison of the 45 community-onset MRSA (CO-MRSA) infections with the 36 hospital-acquired MRSA (HA-MRSA) infections showed several striking contrasts. Most CO-MRSA were recovered from skin and soft tissue infections caused by isolates carrying the Panton-Valentine leucocidin toxin genes, and the majority (84%) of isolates belonged to a single clonal type, ST80-IV, which has been found in the community in other European countries. Clone ST80-IV could be traced in Denmark back to 1993. ST80-IV was rarely found in HA-MRSA infections, which belonged to a large number of clonal types, including some pandemic MRSA clones. The low number of HA-MRSA infections and the diversity of MRSA clones in Danish hospitals may be the result of successful infection control measures that prevent spread of clones in hospitals. The mechanism of spread of the ST80-IV clone in the Danish community is not known, and new control measures are needed to control further spread of this and other CA-MRSA clones.     

Fluorescent amplified-fragment length polymorphism subtyping of the Salmonella enterica serovar enteritidis phage type 4 clone complex

Fluorescent amplified-fragment length polymorphism (FAFLP) analysis, a high-resolution PCR-based genome fingerprinting method, was used to subtype Salmonella enterica serovar Enteritidis phage type 4. This single phage type is responsible for the majority of salmonellosis in Europe. Twenty strains isolated from nine outbreaks, five isolates from sporadic cases of human infection, four strains of poultry origin, and one laboratory-derived strain were comparatively studied by pulsed-field gel electrophoresis (PFGE) and FAFLP analysis. Following macrorestriction with XbaI, PFGE classified 73% of PT4 strains as a single type. FAFLP analysis was carried out with the primer pair EcoRI+0 and MseI+C, by simultaneously sampling 170 to 190 loci throughout the PT4 genome. Twenty-three FAFLP profiles, with 1 to 61 amplified-fragment differences, were found among the 30 strains. The index of discriminatory power of FAFLP analysis was 0.98, compared to 0.47 for PFGE. FAFLP analysis assigned genotypes to each PT4 outbreak, as well as sporadic PT4 infections, a significant development for the epidemiology and control of this zoonotic enteric pathogen.     

Changes in the clonal nature and antibiotic resistance profiles of methicillin-resistant Staphylococcus aureus isolates associated with spread of the EMRSA-15 clone in a tertiary care Portuguese hospital

Two hundred eighty methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates recovered from a tertiary care hospital in Oporto, Portugal, between 2003 and 2005 were studied by a combination of molecular typing techniques in order to investigate the genetic backgrounds associated with the changes in the resistance phenotypes observed since 2001 and compare them to those previously found in the hospital. All MRSA isolates were grouped into resistance profiles for a panel of seven antibiotics and characterized by pulsed-field gel electrophoresis (PFGE) and SCCmec (staphylococcal cassette chromosome mec) typing. Representative isolates of PFGE types were further studied by spa typing and multilocus sequence typing. Our findings clearly document that the increasing isolation of nonmultiresistant MRSA strains was associated with the decline (from 69% in 1996 to 2000 to 12% in 2003 to 2005) and massive replacement of the multiresistant Brazilian clone (ST239-IIIA) by the epidemic EMRSA-15 clone (ST22-IV), in which resistance to antibiotics other than beta-lactams is very rare, as the major clone (80% of isolates). The Iberian clone (ST247-IA), a major clone in 1992 to 1993, was represented in the present study by just one isolate. Two other pandemic MRSA clones were detected, as sporadic isolates, for the first time in our hospital: the New York/Japan (ST5-II) and the EMRSA-16 (ST36-II) clones. Furthermore, the pattern of susceptibility of MRSA isolates both to gentamicin and to trimethoprim-sulfamethoxazole was shown to be an excellent phenotypic marker for the discrimination of the EMRSA-15 clone from other nonmultiresistant MRSA clones present in our hospital.     

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).     

Fluorescent amplified-fragment length polymorphism genotyping of Neisseria meningitidis identifies clones associated with invasive disease

Fluorescent amplified-fragment length polymorphism (FAFLP), a genotyping technique with phylogenetic significance, was applied to 123 isolates of Neisseria meningitidis. Nine of these were from an outbreak in a British university; 9 were from a recent outbreak in Pontypridd, Glamorgan; 15 were from sporadic cases of meningococcal disease; 26 were from the National Collection of Type Cultures; 58 were carrier isolates from Ironville, Derbyshire; 1 was a disease isolate from Ironville; and five were representatives of invasive clones of N. meningitidis. FAFLP analysis results were compared with previously published multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) results. FAFLP was able to identify hypervirulent, hyperendemic lineages (invasive clones) of N. meningitidis as well as did MLST. PFGE did not discriminate between two strains from the outbreak that were classified as similar but distinct by FAFLP. The results suggest that high resolution of N. meningitidis for outbreak and other epidemiological analyses is more cost efficient by FAFLP than by sequencing procedures.     

Replacement of methicillin-resistant Staphylococcus aureus clones in Hungary over time: a 10-year surveillance study

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in Hungary has been increasing and is now close to 20% among invasive isolates of S. aureus . In order to understand the evolution of MRSA in Hungary, two collections of isolates were studied: 22 representatives of a collection of 238 MRSA isolates recovered between 1994 and 1998, and a collection of 299 MRSA isolates recovered between 2001 and 2004. The isolates were first characterised by pulsed-field gel electrophoresis (PFGE) and were distributed into 19 different PFGE patterns. Representatives of each pattern were further characterised by spa typing, multilocus sequence typing (MLST) and staphylococcal cassette chromosome mec (SCC mec ) typing. The Hungarian clone that was predominant in 1994–1998 (PFGE E, ST239-III) had almost disappeared in 2003–2004, being replaced by the Southern German clone (PFGE B, ST228-I) and the New York/Japan epidemic clone (PFGE A, ST5-II), which represented c.  85% of the 2001–2004 isolates. Thus, this study describes, for the first time, the co-dominance and extensive spread of the New York/Japan clone in a European country.     

Persistence of a clone of methicillin-resistant Staphylococcus aureus in a burns unit

A total of 128 MRSA isolates from a burns unit in 1992 and 1997 was studied by resistotyping, plasmid analysis and pulsed-field gel electrophoresis (PFGE) of SmaI-digested chromosomal DNA to ascertain whether a clone of MRSA had persisted in the unit or whether different clones had been introduced at different times. All the MRSA isolates produced beta-lactamase and had high MICs to methicillin (>256 mg/L). All were resistant to tetracycline, kanamycin, cadmium acetate and mercuric chloride. Most were resistant to gentamicin, neomycin, erythromycin, chloramphenicol, trimethoprim, ciprofloxacin, propamidine isethionate and ethidium bromide, and were susceptible to minocycline, vancomycin and teicoplanin. None of the 1992 isolates was resistant to mupirocin, but 56% and 19% of the 1997 isolates expressed high- and low-level mupirocin resistance, respectively. Many of the 1997 isolates had acquired a 38-kb plasmid encoding high-level mupirocin resistance. The 1992 isolates had two main PFGE patterns; 82% of them belonged to PFGE pattern 1. The 1997 isolates had PFGE pattern 1, the same as the majority of the 1992 isolates. All MRSA isolates from both years carried the mecA gene in the same SmaI fragment. These findings demonstrated that a clone of MRSA that was prevalentin the burns unit in 1992 had persisted and became the predominant clone in 1997.     

Clonal types and multidrug resistance patterns of methicillin-resistant Staphylococcus aureus (MRSA) recovered in Italy during the 1990s

A large number (272) of methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered from Italian hospitals during the early and late 1990s were characterized for multidrug resistance pattern and clonal type using a combination of genotyping methods, including pulsed-field gel electrophoresis (PFGE), spaA typing, multilocus sequence typing (MLST), determination of SCC mec type, and hybridization pattern with Tn 554. The majority of MRSA belonged to four genetic lineages: the pandemic Iberian and Brazilian clones, and two unique clonal types-the "Italian" and "Rome" clones of MRSA. The Italian clone carried the SCC mec type I in the genetic background of ST228, which is a double-locus variant of the sequence type of the multidrug-resistant New York/Japanese clone (ST5). The properties of the Rome clone showed several striking similarities to those of the Archaic clone of MRSA that was dominant among MRSA isolates in the mid-1960s to 1970s, but has not been detected since then in recent global surveillance studies.