Phenotypic and Molecular Characterization of Linezolid Resistance in Enterococci Clinical Isolates: Across-sectional Study

Background: Enterococci have emerged as significant nosocomial pathogens. The clinical management of enterococcal infections has become increasingly challenging due to the rise in multidrug resistant strains. Linezolid is considered a last resort therapeutic option. Objective: Determination the prevalence of linezolid resistant enterococci (LRE) in ICU infected patients, their antibiotic susceptibility pattern and the associated resistance genes. Methodology: Enterococci were identified by colonial morphology, Gram stain and biochemical reactions. VITEK®2 compact system was used for species identification. Antibiotic susceptibility testing by disc diffusion method was done for Enterococci. Linezolid resistance was confirmed by measuring minimal inhibitory concentration (MIC) using E-test strips (0.016-256 μg/ml). Conventional PCR was utilized to explore linezolid resistance genes (optr A and poxt A). Results: Sixty-five enterococcal isolates (51 E.faecalis & 14 E. faecium) were recovered from 270 different clinical samples. More than half of the isolated enterococci (61.5 %) were MDR. Among 65 enterococcal isolates ,22 (33.8%) were resistant to linezolid, eleven of which harbored optr A gene while poxt-A gene was detected in 5 isolates. Conclusion: LRE were increasingly reported. Detection of optr A & poxt A genes in LRE is considered an alarm for resistance to the last resort therapeutic option for MDR Enterococci.