The reductive capacity inherent within viable cells can be conveniently measured using the redox indicator, resazurin [14, 15] . Resazurin is soluble in physiologically buffered formulations and can be added directly to growing cultures in a one-step, homogeneous addition. Unlike the tetrazolium chemistries (2,3-bis(2-methoxy-4-nitro-5-sulphophenyl)-5-carboxanilide-2H-tetrazolium (XTT), (4-[3-4-iodophenyl]-2-(4-nitrophenyl)-2H-5-tetrazolio)-1,3-benzene disulfonate) WST-1, 5-(3-carboxymethoxyphenyl)-2-(4, 5-dimethyl-thiazoly)-3-(4-sulfophenyl) tetrazolium, inner salt (MTS) which measure reductive capacity by colorimetric means, the product of resazurin reduction (resorufin) can also be measured using fluorescence with a fluorometer equipped with 560nm excitation and 590nm emission filter set [16] [17] [18] .