Tetrazolium salts (TTZ), such as tetrazolium violet (TV), have been widely used for microbiological
studies. The formation of the colored formazan product due to bacterial reduction of the uncolored
reagent is extensively exploited to stain cells or colonies in agar or on filters. But an important toxic effect
of tetrazolium salts on bacteria exists that limits their use at high concentrations, impairing the efficient
staining of the colonies. This is especially the case for Salmonella spp. where we observed, using a classic
photometric approach and mathematical modeling of the growth, an important impact of tetrazolium
violet on the apparent growth rate below the inhibitory concentration. In this study, we demonstrate that
adding magnesium to the medium in the presence of TV leads to a significant increase in the apparent
growth rate. Moreover, when higher TV concentrations are used which lead to total inhibition of Salmonella
strains, magnesium addition to the culture media allows growth and TV reduction. This effect of
magnesium may allow the use of higher TTZ concentrations in liquid growth media and enhance bacteria
detection capabilities