Detection of Methicillin Resistant Staphylococcus aureus with Reduced Susceptibility to Vancomycin

Abstract

As there is no molecular-based assays available for the detection of hVISA and VISA. However, increasing amounts of data support a number of methods for the screening and confirmation of hVISA and VISA infection. According to CLSI, broth microdilution is considered the gold standard to determine vancomycin MIC. However, because it is time consuming, a considerable number of clinical laboratories do not use it as routine methodology. Other techniques have been widely used, with variable sensitivity and specificity, such as E-test and automated systems. The only CLSI vancomycin screen agar method in place for clinical isolates for the detection of vancomycin resistant S. aureus (VRSA) and possibly VISA is BHI agar containing 6 mg/liter vancomycin (BHIA6V), a method originally established for detection of vancomycin resistance in enterococci , however this method have a very low sensitivity for the detection of h-VISA. The CDC recommends a supplemental test for VISA detection, with the caveat that strains with vancomycin MICs of 4 ug/ml will not be reliably