ABSTRACT
Objective To investigate the genetic polymorphism of mec Ⅰ in the clinical isolates of methicillin-resistant Staphylococcus anreus(MRSA).Methods 40 isolates(MRSA)carrying mecA gene were selected randomly from the clinical isolates of Staphylococcus anreus from Jan,2005 to Aug,2006 in our hospital.The mec Ⅰ gene was detected by PCR followed with sequencing.Staphylococcal cassette chromosome mec(SCCmec)in MRSA were detected by multiplex-PCR.Agar dilution method was used for determining the MICs of oxacillin against MRSA.Results 35 of 40(87.5%)MRSA carried mec Ⅰ gene.All isolates carrying mec Ⅰ gene have mecI 202C→T substitution,which resulted in Gln at 68 aminophenol position replaced by stop condon.32 isolates carried single point mutation.3 isolates carried double-point mutation,including additonal A at 3 positon,A→C at 41 position and C→T at 142 position beside C→T at 202 position,respectively.Among 35 isolates carrying mec Ⅰ gene,there were 27 isolates of SCCmec Ⅲ, 7 isolates of SCCmec Ⅲ A and 1 isolate of SCCmec Ⅱ.Among 5 isolates with deletion of mec Ⅰ gene,there were 3 isolates of SCCmecⅣ,1 isolate of SCCmec Ⅰ and 1 isolate of non-known SCCmec tpye.The MICs of oxacillin were 256-512 ?g/ml,≥512 ?g/ml and 8-256 ?g/ml in 31 isolates with single point mutation at 202 position in mec Ⅰ gene,3 isolates with double-point mutation in mecI gene and 5 isolates with deletion of mec Ⅰ gene,respectively.1 isolate with single point mutation in mec Ⅰ gene had contrary result(MIC
ABSTRACT
Objective To investigate the infections caused by Staphylococcus aureus carrying Panton-Valentine leukocidin(PVL)genes.Methods 26 isolates of Staphylococcus aureus carrying Panton- Valentine leukocidin(PVL)genes were determined by multiplex PCR.Multilocus sequence typing(MLST) was used to determine the STs of the isolates.The genotypes of SCCmec were also determined by another multiplex PCR in the isolates of methicillin-resistant Staphylococcus aureus(MRSA).Results Among 26 isolates,there were 6 isolates of ST88 MRSA,7 isolates of ST88 methicillin-susceptible Staphylococcus aureus (MSSA),5 isolates of ST239 MRSA,5 isolates of ST398 MRSA,1 isolate of ST25 MRSA,1 isolate of ST30 MRSA and 1 isolate of ST59 MRSA.20 isolates were hospital-acquired(HA)which mainly caused pulmonary infection and post-operative pyogenic infection.6 isolates were community-acquired(CA)which mainly caused soft tissue necrosis.Among 19 isolates of MRSA,ST88-SCCmec Ⅲ A,ST239-SCCmec Ⅲ,ST398- SCCmec Ⅳ and ST398-SCCmec Ⅲ were main types.26 isolates were isolated from 14 wards.ST88-SCCmec Ⅲ A-MRSA caused clone spread in maternity department in our hospital.Conclusion ST88,ST239 and ST 398 are main STs in Staphylococcus aureus carrying PVL in our hospital.The isolates not only cause nosocomial infections but also cause community infection.