Rapid separation and quantitation of mixed microorganisms by filtration and bioluminescence

A membrane filtration/bioluminescence system was developed for the differentiation and quantitation of mixed populations of microorganisms. Samples containing microorganisms were filtered through two membrane filters of descending pore size. The microorganisms retained on the filter contain ATP that can be extracted and measured on the filter via the firefly luciferase-luciferin bioluminescence assay. Results, obtained in less than 20 min, show a good correlation (r greater than or equal to 0.95) between the light produced and the number of organisms in the sample. Using these techniques, Escherichia coli can be separated from yeast or mold and measured in samples containing both microorganisms. When lysostaphin is used to selectively lyse Staphylococci on the filter, the specific quantification of these bacteria among other microorganisms can also be accomplished. The filtration/bioluminescence technique offers the potential of being a rapid and sensitive method to differentiate and detect microorganisms, by selective sizing or lysing, in a variety of samples.