Methicillin Resistant Staphylococcus aureus: Inconsistencies in Vancomycin Susceptibility Testing Methods, Limitations and Advantages of each Method
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 met...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
JCDR Research and Publications Private Limited
2015-10-01
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| Series: | Journal of Clinical and Diagnostic Research |
| Subjects: | |
| Online Access: | https://jcdr.net/articles/PDF/6625/10072_CE[Ra1]_F(AK)_PF1(PAK)_PFA(AK)_PF2(PAG).pdf |
| Summary: | 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.
Aim: 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.
Materials and 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.
Conclusion: 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. |
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| ISSN: | 2249-782X 0973-709X |