Background: Methicillin-resistant Staphylococcus aureus  (MRSA) is a major nosocomial pathogen. Various virulence and antiseptic-resistant factors increase the pathogenicity of MRSA strains and allow for increased infection rates.
Purpose: The purpose of this study was to investigate the prevalence and distribution of virulence-associated and antiseptic-resistant genes from epidemic MRSA strains isolated from East China.
Methods: A newly designed multiplex PCR assay was used to assess whether the virulence-associated genes sasX  and pvl  and the chlorhexidine tolerance gene qacA/B  were present in 189 clinical isolates of MRSA. Multilocus sequence typing (MLST) and Staphylococcal protein A (spa ) typing of these isolates were also performed. The frequency of these genes in isolates with epidemic sequence types (STs) was investigated. 
Results: Twenty STs and 36 spa  types with five epidemic clones (ST5-t311, ST59-t437, ST5-t002, ST239-t030, and ST239-t037) were identified. The prevalence of sasX , pvl , and qacA/B  in all isolates was 5.8%, 10.1%, and 20.1%, respectively. The prevalences of these genes in isolates with ST5, ST59, ST239, and other ST genetic backgrounds were all significantly different (P <0.001). Isolates that had the highest frequency of sasX , pvl , or qacA/B  were ST239 (33.3%), ST59 (28.9%), and ST5 (34.1%), respectively. The gene distribution pattern from all of the isolates showed that sasX –pvl –qacA/B +, sasX –pvl +qacA/B –, and sasX +pvl –qacA/B – were closely associated with epidemic clones ST5-t311, ST59-t437, and ST239-t037, respectively.
Conclusion: There are significant differences in the prevalence of virulence-associated and antiseptic-resistant genes in epidemic MRSA strains. Using this information, more effective control and prevention strategies for nosocomial MRSA infections can be developed.
Keywords: MRSA, MLST, virulence genes, sasX , pvl , qacA/B , multiplex PCR