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Application of methylene
blue dye reduction test (MBRT) to determine growth and death
rates of microorganisms
Subir Kumar Nandy and K. V. Venkatesh*
Department
of Chemical Engineering, Indian Institute of Technology,
Bombay, Powai, Mumbai - 400 076, India.
*Corresponding author: E-mail:
venks@che.iitb.ac.in.
Fax: +91-22-2572 6895 / 2572 3480.
Accepted
29 October, 2009 |
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An efficacy
of a compound for antimicrobial characteristics is typically
evaluated through experiments to obtain the minimum
inhibitory concentration (MIC). Similarly, a minimum
activating concentration (MAC) can be obtained for a
compound necessary for growth. We report a protocol for the
determination of MIC and MAC for antibiotic and exhibition
assays, respectively using methylene blue reduction test.
The assay has been demonstrated on the growth of
Escherichia coli on the antibiotic kanamycin, as an
inhibitor, and on vitamin B12, as an activator. The slope of
discoloration of methylene blue was used to determine the
growth and death rates of the organism. The use of the rate
constants to determine MIC/MAC values established a rational
basis for determination of these relevant constants. The
methodology presented here is general and can be easily
adapted to other systems. The dose-response curves for
extent of death / growth can be used to establish the MIC90
or MAC90 for an inhibitor or an activator, respectively. The
methodology presented here rationalizes and standardizes the
antibiotic and exhibition assays. The main advantage of the
reported assay is the rapid and easy determination of the
MIC and MAC values.
Key words:
Escherichia coli,
vitamin B12, kanamycin, minimum inhibitory concentration
(MIC), minimum activating concentration (MAC). |
