Study of the virulence genes and molecular characteristics of Staphylococcus aureus strains / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the molecular characteristics and virulence genes of 488 Staphylococcus aureus ( S.aureus) strains isolated from the People′s Hospital of Huangzhou District in Hubei Province during 2009 to 2013.Methods The minimum inhibitory concentrations (MICs) of Oxacillin and Cefoxitin to S.aureus were determined by agar dilution method .PCR analysis was used for the detection of staphylococcal cassette chromosome mec ( SCCmec ) and multilocus-sequence typing ( MLST ) .Multiplex PCR analysis was performed to detect the 31 common virulence genes .Results A total of 227 methicillin-resistant S.aureus ( MRSA) strains were identified from 488 S.aureus strains with a prevalence rate of 46.5%.The SCCmec Ⅲtype was the prevalent genotype accounting for 81.5% of the 227 MRSA strains, followed by Ⅳtype which accounted for 10.1%.The predominant clonal complex ( CC) of MRSA strains was CC8 accounting for 81.1%, followed by CC59 (4.8%) and CC5 (3.1%).CC1 was the predominant clonal complex of methicillin-sensitive S.aureus (MSSA) strains, accounting for 34.1% of the 261 MSSA strains, followed by CC398 (21.8%), CC121 (14.9%) and CC59 (13.0%).The number of MSSA iso-lates carrying no less than 15 test virulence genes was 109 ( 48 .2%) , which was significantly higher than that of MRSA isolates (28.2%) (P=0.002).A close relationship between the enterotoxins genes (sed, sej and ser) and the CCs of CC8 and CC5 was identified.Exfoliatin genes (eta and etb) and lukED gene were detected only in strains that belonged to CC 1.Strains that belonged to CC 1 and CC59 clones showed higher rates of pvl gene as compared with those belonging to other CCs (P<0.05).Conclusion The prevalence rate of MRSA strains was 46.5%in Huangzhou District, Hubei Province, which was consistent with the na-tional average rate .The predominant genotype of MRSA strains was ST 239-MRSA-SCCmecIII , accounting for 79.3%.Effective measures should be taken by Health sectors to control the spread of MRSA strains .The MSSA isolates carried more virulence genes than MRSA strains .The spectrums of virulence genes were var-ied in strains belong to different CCs clones , indicating the close relationship between virulence genes and genetic backgrounds .