Abstract
Background Staphylococcus aureus causes a variety of severe infections such as bacteremia and sepsis. At present, 60–80% of S. aureus isolates from Taiwan are methicillin resistant (MRSA). It has been shown that certain MRSA clones circulate worldwide. The goals of this study were to identify MRSA clones in Taiwan and to correlate the molecular types of isolates with their phenotypes.MethodsA total of 157 MRSA isolates from bacteremic patients were collected from nine medical centers. They were typed based on polymorphisms in agr, SCCmec, MLST, spa, and dru. Phenotypes characterized included Panton-Valentine leucocidin (pvl), inducible macrolide-lincosamide-streptogramin B resistance (MLSBi), vancomycin (VA) and daptomycin (DAP) minimal inhibitory concentrations (MIC), and superantigenic toxin gene profiles. Difference between two consecutive samples was determined by Mann-Whitney-U test, and difference between two categorical variables was determined by Fisher's exact test.ResultsFour major MRSA clone complexes CC1, CC5, CC8, and CC59 were found, including 4 CC1, 9 CC5, 111 CC8, and 28 CC59 isolates. These clones had the following molecular types: CC1: SCCmecIV and ST573; CC5: SCCmecII and ST5; CC8: SCCmecIII, ST239, and ST241, and CC59: SCCmecIV, SCCmecVT, ST59, and ST338. The toxin gene profiles of these clones were CC1: sec-seg-(sei)-sell-selm-(seln)-selo; CC5: sec-seg-sei-sell-selm-(seln)-selp-tst1; CC8: sea-selk-selq, and CC59: seb-selk-selq. Most isolates with SCCmecVT, ST59, spat437, and dru11 types were pvl + (13 isolates), while multidrug resistance (≥4 antimicrobials) were associated with SCCmecIII, ST239, spa t037, agrI, and dru14 (119 isolates) (p<0.001). One hundred and twenty four isolates with the following molecular types had higher VA MIC: SCCmecII and SCCmecIII; ST5, ST239, and ST241; spa t002, t037, and t421; dru4, dru10, dru12, dru13, and dru14 (p<0.05). No particular molecular types were found to be associated with MLSBi phenotype.ConclusionsFour major MRSA clone complexes were found in Taiwan. Further studies are needed to delineate the evolution of MRSA isolates.
Highlights
Staphylococcus aureus is one of the most common pathogens in both community- and hospital-associated infections [1,2,3]
We found strains with particular molecular types such as ST573 and ST900 were exclusively recovered from one university-affiliated teaching hospital in northern Taiwan (N1), and the ratios of molecularly CA-methicillin resistant (MRSA) stains (ST59, SCCmecIV and VT, and spa t421) were higher than those recovered from other hospitals (Table S2)
These findings showed that the molecular types of MRSA blood isolates were not distributed in the island and the prevalence CA-MRSA might increase in some hospitals, which was compatible with the previous reports [39,40]
Summary
Staphylococcus aureus is one of the most common pathogens in both community- and hospital-associated infections [1,2,3]. Several molecular methods have been developed to type MRSA isolates, including pulsed-field gel electrophoresis (PFGE) [13], multilocus sequence typing (MLST) [14], and typing based on polymorphisms of the following genetic loci: the staphylococcal cassette chromosome mecA (SCCmec) [15], the X region encoding protein A (spa) [16], the mec-associated hypervariable region (dru) [17], and the accessory gene regulator (agr) [18] With these typing methods, some MRSA isolates including the New York/Japan (SCCmecII-ST5-agrII), Hungarian (SCCmecIII-ST239-agrI), and USA 300 (SCCmecIV-ST8-agrI) clones have been identified worldwide [19,20]. The goals of this study were to identify MRSA clones in Taiwan and to correlate the molecular types of isolates with their phenotypes
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