Correlation of Minimum Inhibitory ConcentrationBreakpoints and Methicillin Resistance GeneCarriage in Clinical Isolates of Staphylococcus epidermidis

Staphylococcus epidermidis is the most important member ofcoagulase negative staphylococci responsible for communityand hospital acquired infections. most clinical isolates of s.epidermidis are resistant to methicillin making these infectionsdifficult to treat. in this study, correlation of methicillin resistancephenotype was compared with methicillin resistance(meca) gene carriage in 55 clinical isolates of s. epidermidis.susceptibility was measured by disc diffusion using methicillindiscs, and minimum inhibitory concentrations (mic) weremeasured using broth microdilution. methicillin resistancegene (meca gene) carriage was detected by specific primersand pcr. disc susceptibility results showed 90.9% resistanceto methicillin. considering a mic of 4 ìg/ml, 78.1% of theisolates were methicillin resistant, 76.36% of which carriedthe meca gene. on the other hand, when a breakpoint of 0.5ìg/ml was used, 89.09% were methicillin resistant, of which93.75% were meca positive. there was a better correlationbetween mic of 0.5 ìg/ml with disc diffusion results and mecagene carriage. the findings suggest that despite the usefulnessof molecular methods for rapid diagnosis of virulencegenes, gene carriage does not necessarily account for virulencephenotype. ultimately, gene expression, which is controlledby the environment, would determine the outcome