Cfr Gene-based Detection of Linezolid-Resistant Staphylococcus Aureus in a Tertiary Care Hospital in Western Uttar Pradesh, India

Abstract

Objective Linezolid is an important antimicrobial agent which is active against multidrug-resistant Gram-positive cocci. Methicillin-resistant Staphylococcus aureus (MRSA) cause life-threatening infection, with narrow therapeutic options including linezolid and vancomycin. The presence of cfr (chloramphenicol–florfenicol resistance) and optrA (oxazolidinone phenicol resistance) gene plays a crucial role in linezolid resistance. Materials and Methods A total of 199 clinical isolates were confirmed as S. aureus using GP ID p628 card, followed by antibiotic susceptibility testing using GPAST cards in the Vitek 2 compact system (Biomerieux, France) to determine minimum inhibitory concentration (MIC) of linezolid. An MIC value of ≥8 μg/ml was taken as resistant for linezolid. Furthermore, the presence of cfr and optrA gene was looked for in the clinical isolates of linezolid resistant S. aureus (LRSA). Results LRSA was isolated in 2.5% of clinical samples. All LRSA were also MRSA, and all of them were recovered from indoor samples. The LRSA were 100% susceptible to vancomycin. cfr gene could be detected in 40% of the isolates. However, all our isolates of LRSA were negative for optrA gene. Conclusions Emergence of linezolid resistance in clinical isolates of S. aureus is a matter of therapeutic concern which alerts toward judicious use of linezolid in clinical practice. The presence of cfr gene is the most common mechanism of resistance to linezolid.

Keywords

• cfr gene
• linezolid resistance
• optra gene
• staphylococcus aureus