Abstract
BackgroundVancomycin is the primary treatment for infections caused by methicilin-resistant Staphylococcus aureus (MRSA). The association of vancomycin treatment failures with increased vancomycin minimum inhibitory concentration (MIC) is a well-recognized problem. A number of single-centre studies have identified progressive increases in glycopeptide MICs for S. aureus strains over recent years – a phenomenon known as vancomycin MIC creep. It is unknown if this is a worldwide phenomenon or if it is localized to specific centers.MethodsThe aim of this study was to evaluate the trend of vancomycin MIC for isolates of MRSA over a 3-year period in a tertiary university hospital in Portugal. MRSA isolates from samples of patients admitted from January 2007 to December 2009 were assessed. Etest method was used to determine the respective vancomycin MIC. Only one isolate per patient was included in the final analysis.ResultsA total of 93 MRSA isolates were studied. The vancomycin MICs were 0.75, 1, 1.5 and 2 mg/L for 1 (1.1%), 19 (20.4%), 38 (40.9%), 35 (37.6%) isolates, respectively. During the 3 year period, we observed a significant fluctuation in the rate of MRSA with a vancomycin MIC > 1 mg/L (2007: 86.2%; 2008: 93.3%; 2009: 58.8%, p = 0.002). No MRSA isolate presented a MIC > 2 mg/L.ConclusionsWe were unable to find in our institution data compatible to the presence of vancomycin MIC creep during the study period. This phenomenon seems not to be generalized; as a result each institution should systematically monitor MRSA vancomycin MIC over time.
Highlights
Vancomycin is the primary treatment for infections caused by methicilin-resistant Staphylococcus aureus (MRSA)
During the 3 year study period, we observed a significant fluctuation in the rate of MRSA with a vancomycin minimum inhibitory concentration (MIC) > 1 mg/L (2007: 86.2%, 2008: 93.3%, 2009: 58.8%)
The factors involved in the development of reduced susceptibility to vancomycin and subsequent “glycopeptide MIC creep” are not entirely elucidated, but recognition of the phenomenon is important since it may be a precursor to hVISA and VISA [15]
Summary
Vancomycin is the primary treatment for infections caused by methicilin-resistant Staphylococcus aureus (MRSA). A number of single-centre studies have identified progressive increases in glycopeptide MICs for S. aureus strains over recent years – a phenomenon known as vancomycin MIC creep. It is unknown if this is a worldwide phenomenon or if it is localized to specific centers. Vancomycin, a glycopeptide antimicrobial, was initially used to treat infections with penicillin-resistant Staphylococcus aureus before alternative, less-toxic drugs were introduced [5]. This glycopeptide became vital for the treatment of infections with MRSA [5]. Vancomycin treatment failure in MRSA is not uncommon, even when MRSA is susceptible to vancomycin
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
