Method of determining a viable count using a hydrophobic membrane

A method for obtaining a viable cell count of a sample solution, comprising the steps of:

• (a) filtering the sample solution through a hydrophobic polycarbonate membrane filter, thereby entrapping any microorganisms in the sample solution on an outer surface of said hydrophobic polycarbonate membrane filter;
• (b) applying a solution of a volatilizable alcohol in a fine spray onto said hydrophobic polycarbonate membrane filter, thereby forming droplets at the outer surface, whereby each droplet that contacts a microorganism releases adenosine triphosphate from said microorganism, said droplets subsequently volatilizing to thereby form at least one localized deposit of the released adenosine triphosphate corresponding to each droplet contacting a microorganism on said hydrophobic membrane;
• (c) applying a luciferin-luciferase solution onto said membrane filter as a spray to induce luminescence of each localized deposit of adenosine triphosphate, thereby forming a luminescent spot at each localized deposit;
• and
• (d) identifying each luminescent spot, thereby obtaining a viable cell count of the sample solution.