Molecular characterization of linezolid resistance in clinically significant isolates of coagulase negative Staphylococcus species, a hospital based study from Western Uttar Pradesh

Introduction and aim: The emergence of Multidrug-resistant Coagulase-negative Staphylococcus species is a therapeutic problem. Linezolid-resistant CoNS (LRCoNS) are on a significant rise, with a global prevalence of around 2%. The acquisition of cfr (chloramphenicol-florfenicol resistance) gene  is the commonest  mechanism leading to resistance. This study aimed to determine the molecular characterization of linezolid resistance in clinically significant isolates of Coagulase Negative Staphylococci (CoNS).   Material and Methods: The 1061 clinical  isolates of CoNS were identified by standard bacteriological technique. Antibiotic sensitivity test was performed to determine the susceptibility to linezolid and those isolates with zone diameter 20 mm (linezolid screen positive) were further confirmed by the automated Vitek 2 compact system and MIC 8 microgram per mL was resistant . The cfr gene was detected in phenotypically confirmed LRCoNS.   Results: Resistant to Linezolid was seen in 2.5% of clinically important isolates of Coagulase Negative Staphylococci. The resistance was maximum in S.hemolyticus (70%), followed by S.cohnii (22.2%). Among the LRCoNS, the overall cfr gene was detected in 78% of isolates, predominantly in S.hemolyticus and S. cohnii. All the LRCoNs were also MRCoNS (methicillin resistance). However, all isolates were susceptible to glycopeptides.   Conclusion: There has been a surge of CoNS being reported from clinical samples with resistance to many important antimicrobials, including linezolid. The presence of cfr gene is the most common mechanism of resistance to linezolid. Early and correct identification of these isolates and adherence to infection control protocols will help for better clinical outcomes.