DETECTION OF MECA, FEMA, AND FEMB GENES IN CLINICAL STRAINS OF STAPHYLOCOCCI USING POLYMERASE CHAIN-REACTION

MecA, a structural gene located on the chromosome of Staphylococcus au reus, characterizes methicillin-resistant S. aureus (MRSA), and femA a nd femB(fem) genes encode proteins which influence the level of methic illin resistance of S. aureus. In order to examine effectiveness of de tecting mecA and fern genes in identification of MRSA, the presence of these genes in 237 clinically isolated strains of staphylococci was i nvestigated by polymerase chain reaction (PCR). An amplified mecA DNA fragment of 533 base pairs (bp) was detected in 100% of oxacillin-resi stant S. aureus, in 16.7% of oxacillin-sensitive S. aureus, in 81.5% o f S. epidermidis, and in 58.3% of other coagulase-negative staphylococ ci (CNS). While the PCR product of femA (509 bp) or femB (651 bp) was obtained from almost all the S. aureus strains except for five oxacill in-resistant strains (2.5%), neither of these genes were detected in C NS. Therefore, the detection of femA and femB together with mecA by PC R was considered to be a more reliable indicator to identify MRSA by d ifferentiating it from mecA-positive CNS than single detection of mecA .