BACKGROUND: About 60~70% of hospital isolates of staphylococci are resistant to methicillin. The level of resistance varies from low to high depending upon the genetic background of the strains. The purpose of this study was twofold : (i) to understand the relationship between beta-lactamase and methicillin-resistance genes(mecA, mecI, mecR1, femA) and the level of resistance and (ii) to survey the distribution of mec regulator genes(mec I, mecR1) among methicillin-resistant staphylococci. METHODS: Eighty-three isolates of Staphylococus aureus and 29 of coagulase-negative staphylococci(CNS) at Catholic University Hospital were examined. The level of methicillin resistance was studied using disk diffusion test and agar dilution test. MecA, mecI, mecR1, and femA genes detected by polymerase chain reaction. RESULTS: beta-lactamase production was significantly high in S. aureus and CNS isolates with low-level resistance. MecA and mecR1 genes amplification correlated with the level of resistance in S. aureus and CNS isolates. There was no correlation between the level of resistance and mecI and fem A genes amplification in S. aureus and CNS isolates. Methicillin- resistant S. aureus isolates showed more variety in mec regulator region than methicillin-resistant CNS isolates. CONCLUSION: From this study, we conclude that mecR1 gene could be considered as one of the important factors influencing the level of methicillin resistance in staphylococcal strains.
Agar ; beta-Lactamases ; Diffusion ; Genes, vif ; Methicillin Resistance* ; Methicillin* ; Polymerase Chain Reaction