Iranian Journal of Medical Sciences

Correlation of Minimum Inhibitory Concentration Breakpoints and Methicillin Resistance Gene Carriage in Clinical Isolates of Staphylococcus epidermidis

Document Type : Brief Report(s)

Authors

Department of Microbiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, Iran

Abstract
Staphylococcus epidermidis is the most important member of coagulase negative staphylococci responsible for community and hospital acquired infections. Most clinical isolates of S. epidermidis are resistant to methicillin making these infections difficult to treat. In this study, correlation of methicillin resistance phenotype was compared with methicillin resistance (mecA) gene carriage in 55 clinical isolates of S. epidermidis. Susceptibility was measured by disc diffusion using methicillin discs, and minimum inhibitory concentrations (MIC) were measured using broth microdilution. Methicillin resistance gene (MecA gene) carriage was detected by specific primers and PCR. Disc susceptibility results showed 90.9% resistance to methicillin. Considering a MIC of 4 µg/ml, 78.1% of the isolates were methicillin resistant, 76.36% of which carried the mecA gene. On the other hand, when a breakpoint of 0.5 µg/ml was used, 89.09% were methicillin resistant, of which 93.75% were mecA positive. There was a better correlation between MIC of 0.5 µg/ml with disc diffusion results and mecA gene carriage. The findings suggest that despite the usefulness of molecular methods for rapid diagnosis of virulence genes, gene carriage does not necessarily account for virulence phenotype. Ultimately, gene expression, which is controlled by the environment, would determine the outcome.

Keywords


Volume 36, Issue 3 - Serial Number 3
17
September 2011
Pages 213-216

  • Received 27 April 2014
  • Revised 24 August 2020
  • Accepted 24 December 2018