Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology

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pISSN 2288-0585 eISSN 2288-6850

Evaluation of a Colorimetric Broth Microdilution Method for Antimicrobial Susceptibility Testing Using 2,3,5-Triphenyltetrazolium Chloride

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2007 April Volume 10, Issue 1, pages 49-53


https://doi.org/10.5145/ACM.2007.10.1.49

Evaluation of a Colorimetric Broth Microdilution Method for Antimicrobial Susceptibility Testing Using 2,3,5-Triphenyltetrazolium Chloride

Dae Dong Lee1, Eun Yup Lee1, Seok Hoon Jeong2, Chulhun L. Chang1
Department of Laboratory Medicine, 1Pusan National University School of Medicine, 2Kosin University College of Medicine, Busan, Korea

Abstract

Background: The broth microdilution susceptibility testing method is considered a standard for determining minimum inhibitory concentrations, and the addition of the redox indicator 2,3,5-triphenyltetrazolium chloride (TTC) to the broth microdilution method simplifies and increases its objectivity. The current study evaluated the usefulness of a TTC-modified broth microdilution method for antimicrobial susceptibility test of frequently encountered clinical isolates.

Methods: The minimal inhibitory concentrations (MICs) of 10 antimicrobials for 111 clinical isolates of four bacterial species, Staphylococcus aureus, Escherichia coli, Enterobacter cloacae, and Acinetobacter baumannii, were investigated by a modification of the Clinical and Laboratory Standards Institute (CLSI)-recommended broth microdilution method with the addition of 2,3,5-triphenyltetrazolium chloride (TTC). The inhibitory effects of TTC against 192 strains of 22 bacterial species isolated from clinical specimens were also evaluated.

Results: The number of colonies of all 192 strains of 22 bacterial species grown on TTC-containing Mueller- Hinton agar did not differ from those grown on Mueller-Hinton agar only. The MICs with TTC were within 2 dilutions of those obtained by the CLSI method in 569 (97.6%) of 583 organism-antimicrobial agent combinations.

Conclusions: The colorimetric MIC method using TTC may be a useful surrogate of antimicrobial susceptibility testing for most of the frequently isolated bacteria. (Korean J Clin Microbiol 2007;10:49-53)

Keywords

 Susceptibility tests, Colorimetric assay, 2,3,5-triphenyltetrazolium chloride, Escherichia coli, Staphylococcus aureus, Enterobacter cloacae, Acinetobacter baumannii