Linezolid resistance and antimicrobial susceptibility in Staphylococci isolated from clinical specimens

Abstract

Introduction-Purpose: Having detected linezolid resistance in a number of staphylococcal strains isolated from clinical specimens in our hospital, in this study, we aimed to investigate the resistance profile of staphylococci to linezolid and other antimicrobial drugs. Materials and Methods: A total of 883 staphylococcal strains isolated in the Clinical Microbiology Laboratory taken from various clinical specimens from hospitalized patients in Kartal Dr. Lutfi Kirdar Training and Research Hospital from 1 January 2014 to 31 March 2015 were included in our study. Antimicrobial susceptibilities of these isolates were tested by VITEK2 Automatized System (bioMérieux, France) in addition to conventional methods. The detection of the strains identified as linezolid-resistant was confirmed by Antibiotic Gradient Test (E-Test, bioMérieux, France). Results: Out of the 883 staphylococcal isolates, 183 (20.7%) and 700 (79.3%) were identified as S.aureus and coagulase-negative staphylococci (CNS), respectively. Among them, 14.1% were isolated from intensive care unit (ICU) patients, 79.9% were isolated from blood specimens. Thirty-four per cent of 183 S.aureus isolates and 79% of 700 CNS isolates were found to be methicillin-resistant. Among 125 CNS blood isolates from ICU patients, three (2.4%) isolates were resistant to linezolid. While two of these isolates were methicillin-resistant S.epidermidis, the third isolate was methicillin-resistant S. hominis. Conclusion: Although the rate of resistance to linezolid, an antibiotic used clinically in our country since 2005, appears to be low, it has a potential to increase. Therefore, investigation into resistance is suggested, particularly in case of long-term linezolid use and unresponsiveness to treatment.