Comparison of Different Phenotypic Methods Including E-test, Cefoxitin and Oxacillin Disk Diffusion for Detection of Methicillin Resistant Staphylococcus aureus

Abstract

Introduction: Methicillin-Resistant Staphylococcus aureus (MRSA) has spread throughout the world as a hospital and communityacquired illness. Although, a variety of strategies have been employed, laboratory identification of MRSA remains a difficulty. Aim: To examine several phenotypic approaches for accuracy results, with an (Epsilometer) E-test based method serving as the gold standard for MRSA identification. Materials and Methods: A prospective observational study was conducted in the Microbiology Department of Santosh Medical College, Ghaziabad, Uttar Pradesh, India, from August 2020 to July 2021. Total of 384 isolates S. aureus were identified by using the required samples including pus, swab, blood, wound and urine, etc., which were collected from the Microbiology department and the comparison was done between E-test serving as the gold standard for MRSA identification with Cefoxitin Disk Diffusion (CDD)/Oxacillin Disk Diffusion method (ODD). The diagnostic kit for using E-test in collected samples was purchased from Himedia Laboratries Pvt., Ltd., Mumbai, India (EM0065). The data was calculated by using MS-Excel. Results: A total of 113 strains were revealed to be MRSA in clinical specimens out of 384 isolated S. aureus according to Cefoxitin (disc diffusion method). The gold standard method was chosen to be the E-test, which had found a high sensitivity of 79.8% and a specificity of 94.2% compared to the cefoxitin/ ODD method. Isolates including MRSA were highly susceptible to teicoplanin and linezolid. Conclusion: The present study concludes that E-test (strip) method is a high sensitivity and highly specific for detecting MRSA in comparison to other disk methods used in this study. Due to less number of sample size and lesser time period more studies are needed to establish this fact.

Keywords

• linezolid
• mueller hinton agar
• oxacillin disc test
• resistant
• teicoplanin