The Disc diffusion Vancomycin resistant isolates should be retested using vancomycin Etests and the MICs should be reported. Which one is golden standard method for conforming VRSA?
Dear Saravanan
I think , firstly You must use Disk diffusion test and the MIC according to CLSI guide to determine the resistance and sensitive isolates and the VISA
Never forget to use the control strain for disk diffusion and MIC method.
MIC as per CLSI would be a confirmatory method.
E_test only can confirm résistance go vancomycin or other ATB
Be carreful with type of discs
Etest and MIC methods are good,MIC by Vitek 2 and Micro scan Systems are better.VRSA low resistance(MIC 8-16 mg/L)high resistance MMIC._>32mg/L).
In addition to the disc diffusion tests, you should go ahead and test for the presence of genes that code for resistance to Vancomycin, using polymerase chain reaction (PCR). The commonest is the VanA gene cluster consisting several other genes.
This article might help http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3586877/#B7
According to CLSI, 2015, MIC tests should be performed to determine the susceptibility of all isolates of staphylococci to vancomycin. The disk test does not differentiate vancomycin-susceptible isolates of S. aureus from vancomycin-intermediate isolates, nor does the test differentiate among vancomycin-susceptible, -intermediate, and -resistant isolates of CoNS, all of which will give similar size zones of inhibition.
Can anyone suggest to me a less laborious and fast method to determine MIC? Any other method other than Agar screen test or Broth microdilution?
The gold standard to confirm vancomycin resistance in S.aureus is to determine the MIC (not by E-test) as it can differentiate between Vancomycin Intermediate Resistant S.aureus (VISA) and VRSA
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