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. 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/oxacillin disc diffusion method, isolates including MRSA were highly susceptible to Tiecoplanin 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.

Molecular Characterization of Methicillin-Resistant Staphylococci from the Dairy Value Chain in Two Indian States

“…Overall, when the results of the disc diffusion test and the E-test were compared with the genotypically confirmed methicillin-resistant staphylococci, our results found the E-test to be more in accordance with the presence of mecA or mecC genes in staphylococci as compared to the disc diffusion test. Our results are similar to the findings of Wu et al and Gupta et al that demonstrated that the E-test is the gold standard method for detecting methicillin resistance [ 69 , 70 ] rather than disc diffusion testing. Our finding also supports the use of both oxacillin and cefoxitin in disc diffusion testing to prevent false negatives and that cefoxitin alone is not reliable in predicting the presence of the mecA/mecC gene, also reported by Wu et al [ 69 ].…”