Patent ID: 8148081

Claim:
Method for counting and/or identifying on a membrane gram-negative bacteria initially present in a liquid or gaseous medium, comprising the following steps: (a) filtering said liquid or gaseous medium through a membrane so as to retain on or within the membrane the bacteria present in this medium; (b) contacting said membrane and said bacteria with a permeabilizing composition comprising polyethyleneimine and ethanol; (c) fixing said bacteria to the membrane by means of a crosslinking agent; (d) contacting said bacteria with one or more macromolecules capable of crossing the bacterial walls of gram-negative bacteria fixed to the membrane in step (c), said macromolecules being labeled with a member selected from the group consisting of an enzyme that allows the emission of a light signal and a fluorescent molecule; (e) hybridizing said one or more macromolecules with the nucleic acids of said gram-negative bacteria; (f) detecting the one or more macromolecules having penetrated into said gram-negative bacteria by causing a light signal or fluorescence signal to be generated and detecting said signal; and (g) counting and/or identifying the gram-negative bacteria initially present in said liquid or gaseous medium.