Revealing kinetics of chemical transitions in colorimetric indicators of microorganisms growth based on photometric data from a portable microbiological analyser

Ensemble density-dependent synchronization of mycobacterial growth: BACTEC MGIT 960 fluorescence-based analysis and mathematical modelling of coupled biophysical and chemical processes

“…The respective color change compared to pure resazurin (the control) was determined by applying the automated setup, registering the colour content by the transmitted light intensity. The details of the setup and principle of its operation can be found in the work [28] . The obtained experimental recordings are shown as markers in Figure 7 ; to highlight the interval of interest, the time scale origin is shifted in such a way that t = t 0 corresponds to the beginning of the detectable colour change ≈ 3 days.…”

“…An additional test of the revealed dynamical peculiarities (see Discussion for details) was carried out using the resazurin reduction assay [26] , [27] , and quantitative growth curves were obtained photometrically using a portable colorimetric analyzer [28] .…”

Establishing Compliance between Spectral, Colourimetric and Photometric Indicators in Resazurin Reduction Test

“…For REMA experiments determining the minimal inhibitory concentration (MIC) of the standard first-line anti-tuberculosis drug isoniazid, the standard protocol of the broth microdilution in Middlebrook 7H9 as per the current guidelines of EUCAST [ 42 ] was applied to the reference strain M. tuberculosis H37Rv (ATCC 27294); the microplate was also photographed with the smartphone’s camera. The respective time-dependent photometric curves were obtained with a portable microbiological analyser (patent RU 2 779 840 C1), the construction of the principles of operation of which are described in the work [ 41 ].…”

“…Moreover, the possibility to perform this quantification with single-number intensity results in the further simplification of the registration process by applying yellow-filtered illumination and very cheap semiconductor luxmeters. The latter scheme was tested with the recently developed portable microbiological analyzer [ 41 ] by the case study of the response of the standard strain H37Rv of M. tuberculosis to the serial dilutions of the first-line drug isoniazid. The obtained minimal inhibitory concentration values coincide with the known reference standard, and the response curve is coordinated with the colourimetric curve and, respectively, with the resorufin concentration, indicating the viability of treated bacteria.…”

“…As the first task, we will consider the sequential sets of spectrometric and colour photographic data corresponding to the process of the reduction of resazurin to resorufin by hydrazine hydrate, which is a colourless agent that provides a possibility to establish compliance between the indicators’ concentration changes and changes of intensity in the most appropriate colour space’s channel. During the second stage, we address a more applied problem using the data obtained with the recently developed portable microbiological analyser [ 41 ], which operates with the dynamic registration of the optical density in wells of a microbiological plate illuminated by a colour-filtered light source. Referring to the colourimetric conclusions of the first stage, we aim to explore the possibility of using such a simplified scheme for quantitative determinations of the minimal inhibitory concentration (MIC) by the case study of a drug-affected bacterial culture of Mycobacterium tuberculosis .…”