Comparison of the fluorescent redox dye 5‐cyano‐2,3‐ditolyltetrazolium chloride with p‐iodonitrotetrazolium violet to detect metabolic activity in heat‐stressed Listeria monocytogenes cells

Abstract

The fluorogenic redox indicator 5-cyano-2,3-ditolyltetrazolium chloride (CTC) was compared with the chromogenic p-iodonitrotetrazolium violet (INT) and conventional methods to assess cellular viability. Mild heat treatment was used as well-controlled method for producing non-viable and sub-lethally injured cells. CTC gave an underestimation of the viability of Listeria monocytogenes cells when compared with classical plating methods whereas INT gave an overestimation. However, CTC proved to be a sensitive indicator of uninjured cells. The difference between the total count and the CTC count was equivalent to the injured cell population. The fluorescent formazan formed on reduction of CTC was readily detected with a charge coupled device and cells enumerated automatically using image analysis.

The impact of metabolic state on Cd adsorption onto bacterial cells

“…Therefore, respiration was also measured in treated cultures using a Clark‐type oxygen electrode (YSI 5000) calibrated with air‐saturated water. INT staining was performed following the method of Bovill et al . (1994) where cells treated with a tetrazolium dye were harvested, washed, resuspended in buffer, and examined microscopically for refractile spots diagnostic of metabolic activity.…”

Construction of a simple biocatalyst using psychrophilic bacterial cells and its application for efficient 3-hydroxypropionaldehyde production from glycerol

“…We carried out the CTC staining of cells treated for 5, 10, 15, and 30 min at 45°C to determine heat treatment time for the inactivation of basic metabolism in Ac10-Rif r cells. CTC was converted to the insoluble fluorescent dye CTC-formazan when CTC was reduced as an artificial redox partner instead of the final electron acceptor oxygen by respiring bacteria (Bovill et al 1994). After CTC-staining, the 5-min heat-treated cells showed fluorescence with half intensity compared with that of non-treated reference cells (Figure 2).…”

A study of bacterial culturability during bioaerosol challenge test using a test chamber

“…CTC is reduced by reductases in bacterial metabolic pathways and this reaction generates a red fluorescence by 450-nm excitation (Bovill, Shallcross, & Mackey, 1994;Rodriguez, Phipps, Ishiguro, & Ridgway, 1992). Scheme of bacterial challenge test using a chamber.…”