title: Enhanced tetrazolium violet reduction of Salmonella spp. by magnesium addition to the culture media.
abstract: 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.
authors.affiliation: Université Lyon 1, CNRS, UMR5558, Laboratoire de Biométrie et Biologie Evolutive, F-69622 Villeurbanne, France; CNRS, UMR5558, Laboratoire de Biométrie et Biologie Evolutive, F-69622 Villeurbanne, France; bioMerieux SA département Microbiologie industrielle, Chemin de l'Orme, 69280 Marcy l'Etoile, France. Electronic address: junillon.thomas@hotmail.fr.
authors.forename: Thomas
authors.initials: T
authors.lastname: Junillon
authors.affiliation: bioMerieux SA département Microbiologie industrielle, Chemin de l'Orme, 69280 Marcy l'Etoile, France. Electronic address: luciemorand2@gmail.com.
authors.forename: Lucie
authors.initials: L
authors.lastname: Morand
authors.affiliation: Université Lyon 1, CNRS, UMR5558, Laboratoire de Biométrie et Biologie Evolutive, F-69622 Villeurbanne, France; CNRS, UMR5558, Laboratoire de Biométrie et Biologie Evolutive, F-69622 Villeurbanne, France. Electronic address: jean-pierre.flandrois@univ-lyon1.fr.
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Flandrois
mesh_terms: D003470:Culture Media / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D012475:Salmonella / Q000254:growth & development / Q000378:metabolism*; D013778:Tetrazolium Salts / Q000378:metabolism*
chemical_list: D003470:Culture Media; D013778:Tetrazolium Salts; C531352:tetrazolium violet; D008274:Magnesium
keywords: Growth parameters; Magnesium; Salmonella spp.; Tetrazolium violet