Impact of vancomycin MIC creep on patients with methicillin-resistant Staphylococcus aureus bacteremia

• Published in: Journal of microbiology, immunology and infection immunology and infection, 2012-06, Vol.45 (3), p.214-220
• Main Authors: Yeh, Yen-Cheng, Yeh, Kuo-Ming, Lin, Te-Yu, Chiu, Sheng-Kang, Yang, Ya-Sung, Wang, Yung-Chih, Lin, Jung-Chung
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Analysis of Variance; Anti-Bacterial Agents - pharmacology; Anti-Bacterial Agents - therapeutic use; Bacteremia; Bacteremia - drug therapy; Bacteremia - epidemiology; Bacteremia - microbiology; Chi-Square Distribution; Data processing; Demography; Drug resistance; Drug Resistance, Bacterial; Etest; Female; Humans; Infection; Infectious Disease; Male; Medical Education; Methicillin-resistant Staphylococcus aureus; Methicillin-Resistant Staphylococcus aureus - drug effects; Methicillin-Resistant Staphylococcus aureus - isolation & purification; Microbial Sensitivity Tests; Middle Aged; Minimum inhibitory concentration; Mortality; Retrospective Studies; Standard deviation; Staphylococcal Infections - drug therapy; Staphylococcal Infections - epidemiology; Staphylococcal Infections - microbiology; Staphylococcus aureus; Taiwan - epidemiology; Vancomycin; Vancomycin - pharmacology; Vancomycin - therapeutic use; Vancomycin creep
• ISSN: 1684-1182; 1995-9133
• DOI: 10.1016/j.jmii.2011.11.006

Background/Purpose To date, vancomycin is still the standard treatment for methicillin-resistant Staphylococcus aureus (MRSA) infections, but minimum inhibitory concentration (MIC) creep is becoming a major concern. The aims of this study were to investigate trends in vancomycin use and MIC values over the last decade at our institute and to evaluate the outcomes of bacteremic patients infected with MRSA isolates with reduced vancomycin susceptibility. Methods Vancomycin use and density were evaluated using the defined daily doses (DDD) method. Patients with MRSA bacteremia were enrolled retrospectively. Patient demographic data and clinical outcomes were analyzed. The first isolate from each patient was collected for E-testing in order to determine vancomycin MIC. MIC trends were assessed as MIC50 , MIC90 , and the geometric mean. Results Vancomycin use has increased over the last decade. One hundred and forty patients were enrolled and their respective isolates were retrieved, including isolates from 45 patients in 2001, 46 patients in 2005, and 49 patients in 2009. The geometric mean (± standard deviation) of the vancomycin MIC for MRSA isolates obtained in 2009 was 1.39 ± 0.30 μg/mL, which is significantly higher than the mean vancomycin MIC obtained in 2001 (1.19 ± 0.34 μg/mL, p