ABSTRACT
Objective To reversing methicillin-resistant Staphylococcus(MRS) to methicillin-susceptible Staphylococcus(MSS) by changing nutritional conditions and continuous transfer of culture .Methods MRS trains separating from clinical specimens were cultured in different conditions ,continuous cultural transfer ,and drug sensitive test were proceeded periodically to observe the phe-notypic and chemical reaction change of MRS .The mecA gene were detected of the original and mutant strains by polymerase chain reaction(PCR) ,then the gene sequenced and compared .Results 53 MRS strains were studied .6 strains were phenotype successful-ly converted to MSS in different cultural conditions ,among them mecA gene was undetected in 2 strains ,and down expressed in 4 strains .Conclusion The MRS strains separated from clinical specimens may revert to MSS by culture under different nutritional conditions .The mecA gene of MRS may be lost or lower expressed and the MRS and mutant strains may be different in genomics .