Along traditional culture based methods more rapid methods for detection of viability of microbes are needed. Several fluorescent stains are on the market e.g. for indication of metabolic activity and viability of microbes or for the measurement of integrity of cell membranes. Applications include assessment of viability of beneficial microbes as well as revealing the mode of action of antimicrobial agents against harmful bacteria. Fluorescence of the fluorochromes can be detected with various methods, e.g. epifluorescence microscope, flow cytometer or fluorescence microplate reader.