Changes in antimicrobial resistance of Enterococcus spp. Over a few years.

In this study, we aimed to review the resistance rates of high-level aminoglycosides compared to the resistance rates of other antimicrobials and review the trends in minimum inhibitory concentration (MIC) for 4 years in enterococci isolates. In the study, 2898 enterococci isolates from clinical specimens in the microbiology laboratory from 2008-2011 were evaluated retrospectively. The identification and antimicrobial susceptibility of the isolates were studied in Phoenix (BD, USA) automated system. MIC50 and MIC90 of the isolates were determined. The distribution of specimens were as follows; 60.6% urine, 18.8% blood, 11.7% wound, 5.7% sterile body fluids, and 3% catheter tips. The resistance rates were for ampicillin, vancomycin, teicoplanin, linezolid, high level gentamicin (HLG) and high level streptomycin (HLS) were determined as: 46%, 14.4%, 15.1%, 1.3%, 44.7%, and 56.5% respectively. MIC50 of the linezolid was determined as 2 μg/ml for four years and MIC90 was determined as 4 μg/ml for 2008, 2009, 2010 and 2 μg/ml for 2011. MIC50 of the ampicillin was determined as 4 μg/ml for 2008 and 2011 and 2μg/ml for 2009 and 2011; MIC90 was determined as 16 μg/ml for four years. MIC50 value of vancomycin was not changed for four years and determined as 1 μg/ml; MIC90 was determined as 32 μg/ml for 2008, 2010, 2011 and 8 μg/ml for 2009. MIC50 value for teicoplanin was determined as 1 μg/ ml for four years; MIC90 was determined as 2 μg/ml for 20096 and 32 μg/ml for other years. In the MIC values of vancomycin significance decrease was seen in 2009 (p<0.001) but after this year a significant increase (p<0.001) was determined. In the MIC values of linezolid a significant increase was determined in 2009 and 2010. A significant decrease, however, was seen in 2011.