title: Methicillin Resistant Staphylococcus aureus: Inconsistencies in Vancomycin Susceptibility Testing Methods, Limitations and Advantages of each Method.
abstract: BACKGROUND
  Vancomycin may be ineffective against an increasing proportion of methicillin resistant Staphylococcus aureus (MRSA) with minimum inhibitory concentrations (MICs) well within the susceptible range. On the other hand it is common knowledge that determination of vancomycin MICs is method dependent. Therefore, given the apparent variability in vancomycin MIC results obtained with the different methods, the use of the vancomycin MIC to predict the outcome of serious S. aureus infections needs to take into account the method used and the results of studies using that particular method.
  
  
  OBJECTIVE
  Comparative study was carried out to evaluate the MICs obtained by BMD method, E-test, and Vitek 2 method and to detect inconsistencies in these vancomycin for 66 MRSA isolates obtained from various samples of patients attending the OPDs & IPDs within a period of one year.
  
  
  METHODS
  A comparative study was carried out to evaluate the MICs obtained by BMD method, E-test, and Vitek 2 method to detect vancomycin susceptibility in 66 clinical isolates of MRSA obtained from various samples of patients attending the OPDs & IPDs within a period of one year. The study was conducted in Department of Microbiology, Subharti Medical College, Meerut from January to December 2012.
  
  
  RESULTS
  On determination of MICs for vancomycin for the MRSA isolates, all were identified as VSSA by BMD, E-Test & Vitek 2 methods. However, the vancomycin MIC values obtained by E-test correlated better with BMD method (correlation factor= 0.6727) than Vitek 2 (correlation factor=0.5316), indicating E-Test to be a better method for determination of vancomycin MICs as compared to Vitek 2.
  
  
  CONCLUSIONS
  MRSA isolates with higher vancomycin MICs, even within the susceptibility range, are being observed more frequently which result in treatment failures with vancomycin. Because of the discrepancy that exists in vancomycin MIC results from different methods, the prediction of outcome of serious S.aureus infections should take into account the method used & results of studies using that particular method.
authors.affiliation: Post Graduate Resident, Department of Microbiology, Subharti Medical College , Meerut, India .
authors.lastname: Himani
authors.affiliation: Assistant Professor, Department of Microbiology, Subharti Medical College , Meerut, India .
authors.forename: Charu
authors.initials: C
authors.lastname: Agrawal
authors.affiliation: Professor and Head of the Department, Department of Microbiology, Subharti Medical College , Meerut, India .
authors.forename: Molly
authors.initials: M
authors.lastname: Madan
authors.affiliation: Professor, Department of Microbiology, Subharti Medical College , Meerut, India .
authors.forename: Anita
authors.initials: A
authors.lastname: Pandey
authors.affiliation: Associate Professor, Department of Microbiology, SubhartiMedical College , Meerut, India .
authors.forename: Bhaskar
authors.initials: B
authors.lastname: Thakuria
keywords: BMD; E-Test; MRSA; Minimum inhibitory concentration; Vitek 2