Comparison of polymerase chain reaction and conventional methods in detecting methicillin-resistant Staphylococcus aureus

Yasar Nakipoglu,Zeynep Ceren Karahan,Riza Adaleti,Cihan Tasdemir,Fatma Kaya

doi:10.3855/jidc.321

Abstract

Accurate and rapid detection of methicillin-resistant Staphylococcus aureus is very important in a clinical laboratory setting to avoid treatment failure. Conventional methods were compared against the gold standard polymerase chain reaction (PCR) technique to determine the best combination of the routine procedures. Methicillin resistance was investigated in 416 clinical Staphylococcus aureus isolates by PCR, oxacillin agar screening (OAS), oxacillin disk diffusion (ODD) and cefoxitin disk diffusion (CDD) methods. Two hundred and ten (51%) out of 416 S. aureus strains were found to be mecA-positive by PCR. Sensitivity and specificity of the ODD, CDD and OAS methods were detected as follows: 100% and 89%, 99.50% and 100%, and 99.50% and 100%, respectively. Combining the ODD and CDD methods could be a good choice for detecting methicillin resistance in S. aureus strains where mecA PCR cannot be performed.

Highlights

Since first reported in 1961, methicillinresistant Staphylococcus aureus (MRSA) have become a major nosocomial pathogen worldwide [1]
Methicillin resistance in S. aureus strains in our department is routinely demonstrated by oxacillin disk diffusion (ODD) method for clinical S. aureus isolates and oxacillin agar screening (OAS) method is used in case of screening for nasal carriers of MRSA
Accurate and early determination of methicillin resistance is of key importance in the prognosis of infections caused by S. aureus

Summary

Introduction

Since first reported in 1961, methicillinresistant Staphylococcus aureus (MRSA) have become a major nosocomial pathogen worldwide [1]. Genotypic tests involving detection of mecA gene by polymerase chain reaction (PCR) are the preferred methods [5,6], but they are not practical for routine use in many clinical laboratories. Accepted phenotypic methods used for detecting MRSA strains include oxacillin disk diffusion (ODD), oxacillin agar screening (OAS) methods, and determination of minimal inhibition concentration (MIC) of oxacillin by broth dilution or E-test method. Methodology: Methicillin resistance was investigated in 416 clinical Staphylococcus aureus isolates by PCR, oxacillin agar screening (OAS), oxacillin disk diffusion (ODD) and cefoxitin disk diffusion (CDD) methods. Conclusion: Combining the ODD and CDD methods could be a good choice for detecting methicillin resistance in S. aureus strains where mecA PCR cannot be performed.

Methods

Results

Conclusion