GLYCOPEPTIDES AND LINEZOLID MIC CHANGES IN STAPHYLOCOCCUS AUREUS AND COAGULASE NEGATIVE STAPHYLOCOCCI ISOLATES FROM 2008-2011 KERAMETTIN Y ANIK 1 , HAVA YILMAZ 2 , YELIZ T ANRIVERDI CAYCI 3 , ADIL KARADAG 1 , SABAN ESEN 2 , MURAT GUNAYDIN 4 1 Department of Medical Microbiology, Faculty of Medicine, OndokuzMayis University, Samsun - 2 Departmet of Infectious Diseases and Clinical Microbiology,Faculty of Medicine, OndokuzMayis University, Samsun - 3 Department of Microbiology, Ankara Occupational Diseases Hospital, Ankara - 4 Istanbul University, Medical Faculty of Cerrahpasa, Department of Medical Microbiology, Istanbul, Turkey Introduction Staphylococcus aureus is an important pathogen both in hospital and community-acquired infections in worldwide (1) . The mortality of S. aureus bacteremia, before the penicillin,was 80%. After the introduction of penicillin in 1940s, prog- nosis of patients with staphylococcal infections improved dramatically but, in 1942, first penicillin resistant isolate was determined. Methicillin is an semisynthetic penicillinase-resistant antimicrobial and was introduced in 1961, however methicillin resistant isolates were rapidly spread in both hospi- tal and community.Methicillin resistant S. aureus (MRSA) is an important clinical problem due to multidrug resistance patterns of MRSA isolates (2,3) . In the recent studies, it has been determined that 60% of the S. aureus were isolated from inten- sive care units (4) . Glycopeptides are effective agents preferred in the treatment of MRSA infections (4) .However in 1990s glycopeptides resistant and heteroresistant isolates were reported (5,6,7,8) . In recent years new antistaphylococcal antibi- otics such as linezolid, the first oxazolidinone, were introduced as a therapeutic option in thetreatment of MRSA infections (9) . Glycopeptide resistant or intermediate isolates are rare among S. aureus clinical samples, but it is an emerging concern that vancomycin therapy failed in patients, with vancomycin MICs at the high end of the Clinical Laboratory and Standarts Institute (CLSI) susceptibility range (10) . In this study we aimed to investigate changes in MICs of vancomycin, teicoplanin and linezolid. Acta Medica Mediterranea, 2014, 30: 995 ABSTRACT Aims: Glycopeptides and linezolid are the antimicrobial agents used for the treatment of methicillin resistant Staphylococcus aureus (MRSA) and methicillin resistant Coagulase negative Staphylococci (MRCoNS) infections. It is emerging concern about an increase minimum inhibitor concentration (MIC) of vacomycin among S. aureus strains. In this study, we aimed to analyse the trends in MICs of vancomycin, teicoplanin and linezolid over 4 years (2008-2011) period. Materials and methods: Identification and MICs of the isolates were tested in Vitek2 Compaktand Phoenix (Becton Dickinson, Diagnostic Systems, USA) automated systems. MIC50 (defined as the minimum concentration at which 50% of the isolates were inhibited), MIC90 (defined as the minimum concentration at which 90% of the isolates were inhibited) and mean MICs were evalua- ted. All calculations were performed for each year. Results and conclusion: No vancomycin, teicoplanin and linezolid resistant isolates were detected. The decreased in the mean MIC of vancomycin in S. aureus isolates over 4 years, was found significant. The increased, in the mean MIC of vancomycin in CoNS isolates among 2008-2009, was significant. Otherwise, the decrease in the mean MIC of teicoplanin and linezolid in S. aureus isola- tes, was significant among 2009-2010. Key words: S. aureus, vancomycin, teicoplanin, linezolid, MIC. Received February 18, 2014; Accepted June 19, 2014