The Multi-Drug Resistance CFR Gene : An Evolving Mechanism for Linezolid Resistance in Staphylococcus Aureus

Background: The emergence of linezolid resistance conveyed by the cfr (chloramphenicol-florfenicol resistance) gene in Staphylococcus aureus possess an utmost importance attributable to its ease of spread. Objectives: This study was undertaken for (1) evaluation of the susceptibility of S. aureus clinical isolates from Mansoura University Hospital (MUH), Mansoura, Egypt to linezolid, (2) detection of the risk factors associated with the emergence of linezolid-resistant S. aureus (LRSA) isolates, and (3) detection of the cfr gene encoding for linezolid resistance. Methodology: During the study period, clinical samples were collected from patients admitted to MUH. Antimicrobial susceptibility was assessed by the Kirby-Bauer's disc diffusion method. The minimum inhibitory concentrations (MICs) of linezolid were determined by agar dilution (AD) method. Polymerase chain reaction (PCR) was used for detection of the cfr gene encoding for linezolid resistance. Results: Out of 197 S. aureus isolates, an overall linezolid resistance of 8.1% was perceived by AD method. Among the risk factors associated with acquisition of LRSA, only hospital stay > 2 weeks retained significance in the logistic regression model (P = 0.002). The cfr gene was detected in 37.5% of LRSA isolates by PCR. Conclusion: The existent study disclosed that the presence of cfr gene is a leading mechanism conferring linezolid resistance in S. aureus. Thereby, prudent consumption of linezolid and ongoing surveillance of cfr-positive strains are crucial to prevent the dissemination of cfr-harboring strains in healthcare-settings.