Correlation between oxacillin MIC values with those of linezolid against clinical isolates of MRSA

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Original Article

Author Details : Arulkavi Arumugam*, Sandhya Bhat, Reba Kanungo

Volume : 10, Issue : 4, Year : 2023

Article Page : 216-221

https://doi.org/10.18231/j.ijmr.2023.038

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Abstract

Background: Infection by methicillin-resistant Staphylococcus aureus (MRSA) is a great threat to medical care facilities and also in communities, due to its multidrug resistance to commonly used antimicrobial agents. The overuse of glycopeptide antibiotics, such as vancomycin and linezolid, has led to the emergence of reduced susceptibility to these anti-MRSA agents, which in turn may lead to therapeutic failure. This study has been conducted to explore the correlation if any, of MIC of oxacillin to the MIC of linezolid in clinically significant isolates of MRSA in a tertiary care hospital.
Materials and Methods: The study was carried out over the period of two months after obtaining a waiver of consent from the Institute Ethics Committee. Seventy-five clinically significant MRSA isolates were included in the study. All MRSA isolates were subjected to cefoxitin and linezolid antibiotic disk susceptibility testing. Minimum inhibitory concentration (MIC) to oxacillin and linezolid was performed by the agar dilution method. The MIC and MIC were also recorded both for oxacillin and linezolid MIC among these MRSA isolates. Correlation between oxacillin MIC and linezolid MIC was estimated using the Pearson correlation coefficient, r.
Themajority of MRSA isolates (41%) were isolated from skin and soft tissue infections (SSTIs) (40%). MIC values for oxacillin ranged from 4 ?g/mL to >32?g/mL and MIC values for linezolid ranged from ? 0.25µg/mL to 4 µg/mL. The majority of these isolates (40%) had linezolid MIC of ? 0.25µg/mL. All the isolates were uniformly susceptible to linezolid. Pearson correlation coefficient, r was 0.41, between oxacillin MICs and linezolid MICs, which indicated poor correlation.
Conclusion: Although we did not observe any resistance to linezolid among the MRSA isolates, we should monitor carefully the antibiotic selection pressure and creeping MIC, to aid in the early detection of the emergence of resistance.
 

Keywords: MRSA, MIC creep, Linezolid, Oxacillin, Antimicrobial susceptibility testing.

How to cite : Arumugam A, Bhat S, Kanungo R, Correlation between oxacillin MIC values with those of linezolid against clinical isolates of MRSA. Indian J Microbiol Res 2023;10(4):216-221

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