Molecular typing and drug resistance of methicillin-resistant Staphylococcus aureus in Zhejiang province / 中华临床感染病杂志

ABSTRACT

Objective To investigate molecular types and drug resistance of methicillin-resistant Staphylococcus aureus (MRSA) in Zhejiang province.Methods One hundred and fourty-seven clinical MRSA isolates were collected from 11 grade A tertiary hospitals during January 2009 and December 2010 in Zhejiang province.Minimal inhibitory concentrations (MICs) of 13 antimicrobial agents were determined by agar dilution.Multilocus sequence typing (MLST),staphylococcal cassette chromosome mec (SCCmec) typing and spa typing were used to examine the homology of the strains,and drug resistance patterns were compared among different molecular types.Simpson index was used to determine the discriminatory power of three typing methods.Results Fourteen STs were identified in 147 MRSA isolates,of which ST239 (75 isolates),ST5 (24 isolates) and ST59 (23 isolates) were the most prevalent clones.Four SCCmec types (types Ⅱ to Ⅴ) were identified in 141 isolates,and 6 isolates were not typed.SCCmec type Ⅲ was the predominant type (76 isolates),which was followed by type Ⅳ (32 isolates),type Ⅱ (24 isolates) and type Ⅴ (9 isolates).All MRSA isolates yielded 23 spa types,in which t030 (57 strains),t437 (17 strains),t002 (15 strains) and t037 (12 strains) were the predominant spa types.MRSA strains were sensitive to linezolid,teicoplanin,vancomycin and norvancomycin,but were highly resistant to other antibacterial agents,especially in strains carrying clone ST239 or of SCCmec type Ⅲ.The discriminatory power of MLST,SCCmec and spa typing were 0.6885,0.6577 and 0.8165,respectively.Conclusion The predominant clone of MRSA strains in Zhejiang province was ST239-SCCmec Ⅲ-t030-MRSA,and these strains are highly resistant to most antibacterial agents,so that the surveillance of MRSA in hospital should be strengthened.