The tetrazolium salt-based method is widely used to measure living cells in
planktonic microbial cultures (Kuhn, Balkis et al. 2003, Cerca, Martins et al.
2005)(5-6) and to measure growth in bacterial (Johansen, Falholt et al. 1997, Xu,
McFeters et al. 2000, Shakeri, Kermanshahi et al. 2007, Rändler, Matthes et al. 2010,
Nett, Cain et al. 2011)(7-8-9-10-11) and Yeast biofilms (Ramage, Vande Walle et
al. 2001, Tsukatani, Higuchi et al. 2009, Taff, Nett et al. 2012)(12-13-14). To date,
the most widely used tetrazolium among colorimetric assays is to test the
antimicrobial susceptibility of bacteria and fungi with XTT salt, which, after
reduction, produces a water-soluble derivative that can be easily measured (Honraet,
Goetghebeur et al. 2005)(15). Despite the popularity of this compound, XTT is
expensive and problems with intraspecific and interspecific changes have been
reported (Minnikin, Alshamaony et al. 1975, Cerca, Martins et al. 2005)(6-16).

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