The emergence of Staphylococcus strains resistant to methicillin 
   occurred shortly after the introduction of methicillin into clinical use .

   Resistance to methicillin in clinical isolates of Staphylococci has been
   explained by the production of a characteristic penicillin-binding protein
   (PBP) , designated PBP2a, that has a decreased binding affinity for b-lactam
   antibiotics, the gene mec-A encoding PBP2a was cloned and is distributed
   among methicillin- resistant but not methicillin-susceptible populations of S.
   aureus. Recently, high prevalence of methicillin resistance has been noticed
   in the clinical isolates of coagulase-negative Staphylococci (CNS) which,
   besides MRSA( Methicillin- Resistant -Staphylococcus aureus), also have
   been recognized as important nosocomial pathogens .

          Detection of the mec-A using PCR may provide a sensitive method for
   identifying methicillin resistant Staphylococci .

          In this study, overall 268 wound swabs in which 107 cases (40%) were
   Staphylococcus aureus and 10 cases (3.7%) were coagulase negative
   Staphylococcus and the rest of them  were other microorganisms  were
   examined .

       After the extraction of DNA  , PCR was carried out using specific primers.
   The results indicated that the mec-A was present in 24 cases ( 9% ) . In  8
   cases (34%)   Staphylococcus aureus ,3 cases (12%) coagulase negative
   Staphylococci , the others were related to another microorgamisms that
   probably were contaminated by Staphylococcus species.