Volume 46, No. 06, Month DECEMBER, Year 2020, Pages 665 - 670

Evaluation of 3 4 5 dimethyl 2 thiazolyl 2 5 diphenyl tetrazolium bromide method for rapid detection of vancomycin resistant enterococci

Nucharat Panthasri, Prajuab Chaimanee, Suthida Kenprom, Patcharaporn Tippayawat, Nicha Charoensri, Aroonwadee Chanawong, Ratree Tavichakorntrakool, Aroonlug Lulitanond

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Vancomycin-resistant enterococci (VRE) have become a global problem of hospital-associated infections. A rapid VRE detection and early isolation of the positive cases are essential for prevention and control of their transmission in hospitals. The aim of this study was to develop and evaluate a simple and rapid method for detection of VRE by using 3 (4, 5 dimethyl-2-thiazolyl)-2, 5 diphenyl tetrazolium bromide (MTT) colorimetric method compared with standard broth microdilution (BMD) and Epsilometer test (Etest). A total of 85 Enterococcus isolates (75 vancomycinnon-susceptible, 2 vancomycin-intermediate and 8 vancomycin-susceptible) were studied. The minimum inhibitory concentrations (MICs) of vancomycin for all isolates were tested by BMD, MTT and Etest methods. The MTT method gave results within 9 h with good category agreement, essential agreement, very major, major, and minor errors (100, 92.9, 0, 0 and 7.1%, respectively), which were comparable to those of the Etest (97.6, 95.3, 2.4, 0 and 4.7%, respectively). The Cohen?s kappa coefficient (?) of the MTT method compared with the BMD showed perfect agreement (1.000) (p < 0.001). The MTT method is simple and rapid for early VRE detection to support prevention and control the spread of the enterococci in hospitals.


vancomycin resistance, enterococci, Etest, broth microdilution, MTT


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