Investigation of activity of tigecycline against methicillin-resistant Staphylococci strains.

Abstract

OBJECTIVE: Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-resistant coagulase negative staphylococci (MRCNS) are important cause of infections worldwide. Vancomycin and other glycopeptide antibiotics are mainstay of therapy for infections caused by MRSA and MRCNS. High prevalence of methicillin resistant staphylococci strains led to increased use of vancomycin. This situation caused to reduction of glycopeptide susceptibility in methicillin-resistant staphylococci. Treatment options of infections due to MRSA with reduced susceptibility to vancomycin are limited. Tigecycline should be take into consideration as an antimicobial therapeutic alternative for infecitons caused by MRSA and/or MRCNS. The aim of this study was to determine in vitro antimicrobial activity of tigecycline against methicillin-resistant staphylococci strains isolated from various clinical specimens. METHODS: Staphylococcus strains isolated at the Microbiology Laboratory of Konya Education and Research Hospital in between January and December in 2010. The isolated strains were identified by using both conventional methods and fully automated bacteria identification and susceptibility system (Phoenix 100, BD, Sparks, USA). Methicillin resistance was determined and evaluated according to Clinical and Laboratory Standards Institute (CLSI) instrucions by using disc diffusion method (oxacillin 1 μg and cefoxitin 30 μg discs) Minimum inhibitory concentration (MIC) values of tigecycline for isolated strains were detected with E-test method (bio-Merieux Marcy l Etoile, France). RESULTS: Of all the eighty five methicillin-resistant staphylococci strains 35 (41%) were identified as Staphylococcus aureus and 50 (59%) coagulase negative staphylococci. MIC values of tigecycline for the 35 MRSA isolates were MIC50: 0.094 μg/ml, MIC90: 0.5 μg/ml) and for the 50 MRCNS isolates were MIC50: 0.047 μg/ml, MIC90: 0.25 μg/ml. All isolates (100%) were found to be sensitive to tigecycline. CONCLUSION: Results of this study showed that tigecycline was effective in vitro antimicrobial activity against both MRSA and MRCNS isolates. Tigecycline may be preferred as a last choice in the treatment of resistant infections due to the MRSA and MRCNS that alternative antibiotics were all resistant.