Determination of In Vitro Activity of Linezolid in Resistance Gram-positive Bacteria by E-Test Method

Özet

Introduction: The incidence of infections caused by multidrug-resistant Gram-positive bacteria is increasing in the past years. The pathogens such as glycopeptid-resistant enterococci, methicillin-resistant Staphylococcus aureus (MRSA), and coagulase-negative staphylococci (CoNS) have emerged widely and they contribute an increase. The treatment of the patients infected with the multidrug-resistant pathogens is extremely difficult. The aim of this study was to determine in vitro susceptibility of vancomycin-resistant enterococci (VRE) and staphylococci against linezolid that may provide new alternative to treat. Methods: A total of 80 isolates of staphylococci (30 MRSA, 30 MSSA, and 20 Methicillin-resistant coagulase-negative staphylococci [MRCoNS]) obtained from various clinical specimens and 20 VRE isolates recovered from blood and rectal swab specimens were sent to our microbiology laboratory. Linezolid susceptibility was determined by disc diffusion methods and E-test for all isolates. In addition, for all isolates, sensitivity to other antibacterials was detected by Kirby–Bauer disc diffusion method according to guidelines established by the Clinical and Laboratory Standards Institute. Results: The results showed that all strains were fully susceptible to linezolid (minimal inhibitory concentration [MIC] ≤2 μG/ml). The linezolid effectiveness is not different between the MRSA and MSSA strains. MICs were changed for MRSA from 0.018 to 2 μg/ml, MSSA from 0.25 to 1.5 μg/ml, and MRCoNS from 0.19 to 1 μg/ml. MICs were changed from 0.38 to 2 μg/ ml for VRE strains. Discussion and Conclusion: As a result of the present study, it was decided that linezolid appears to be a good alternative in the treatment of infections caused by Gram-positive bacteria, especially those resistant to glycopeptides or with reduced sensitivity.