ISSN: 0973-7510

E-ISSN: 2581-690X

Research Article | Open Access
Eeshita Dhar1, A. Tejashree1 , M.V.S. Krishna Karthik1 and Pushkal Sinduvadi Ramesh2
1Department of Microbiology, JSS Medical college and Hospital, JSS AHER, Mysore, Karnataka, India.
2Center of Excellence in Molecular Biology and Regenerative Medicine (DST-FIST sponsored center), Department of Biochemistry, JSS Medical College, JSS AHER, Mysore, Karnataka, India.
Article Number: 8435 | © The Author(s). 2023
J Pure Appl Microbiol. 2023;17(3):1509-1515.
Received: 17 January 2023 | Accepted: 28 June 2023 | Published online: 28 July 2023
Issue online: September 2023

Staphylococcus aureus strains that are mecA and PBP2a positive but phenotypically susceptible to oxacillin are becoming more and more abundant, according to research from all around the world. The oxacillin susceptibility of Staphylococcus aureus (OS-MRSA) contributes to consequent treatment-failure due to misidentification by conventional susceptibility tests. Therefore, the objective of the current study was to ascertain the prevalence of OSMRSA in a tertiary care facility located in Mysore, South India. 395 MRSA isolates collected from diverse clinical samples were included in this lab-based prospective investigation. These isolates were tested using an oxacillin 1μg disc phenotypically by standard disc diffusion test, and simultaneously MIC to Oxacillin was determined from Vitek2 systems. Additionally, MRSA specific mecA gene detection was applied to these isolates in order to confirm their MRSA status genotypically. PCR findings demonstrate that 65% of the isolates were MRSA. The vitek2 system detected 4.06% OS-MRSA isolates with an oxacillin MIC of ≤2µg/ml. The disc diffusion method identified a total of 13.75% isolates as oxacillin sensitive and 10% isolates were oxacillin intermediately sensitive. Oxacillin sensitivity was shown for 1.87% of the mecA-positive MRSA isolates using the VITEK2 and disc diffusion techniques. This analysis found isolates with lower oxacillin MICs but relatively reduced OS-MRSA incidence. Using an oxacillin disc for routine laboratory MRSA detection might occasionally produce false negative results, which can result in improper antibiotic administration and treatment failure. In order to distinguish OS-MRSA from MRSA, it is crucial to combine phenotypic and genotypic techniques.


Oxacillin Sensitive-MRSA (OS-MRSA), mecA Gene, PCR, MRSA, Vitek 2 System, MIC

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© The Author(s) 2023. Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License which permits unrestricted use, sharing, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.