A method for characterizing the presence or absence of a microorganism in a biological medium

The present invention relates to a method for detecting the presence or absence of a microorganism, said method comprising the steps of 1) providing an enclosure containing a liquid or semi-solid phase formed of an organic medium which may contain a living form of said microorganism, nutrient, and an enzyme substrate specific for said microorganism and metabolizable in at least one VOC metabolite, and a gas phase contiguous with said liquid or semi-solid phase, 2) exposing at least said liquid phase or semi-solid at the conditions for the metabolization of said enzyme substrate with said microorganism, in one molecule of said metabolite VOC and 3) reveal optical transduction, the presence or absence of said VOC metabolite characterized in that it interacts with a nanoporous matrix, and in that the detection optical transducing a change in the optical properties of said matrix is indicative of an interaction of said matrix with said metabolite.