Method for the detection and enumeration of viable microorganisms. A liquid that comprises one or more markers incorporated in a liquid sol-gel precursor, is provided. A transparent slide is coated with a thin uniform layer of the liquid sol-gel precursor composition. The microorganisms are separated from liquid sample to be analyzed by passing the sample through a filter, and then bringing the filter into close contact with the sol-gel coated slide. The filter is co-incubated with the sol-gel coated slide for a period of time and at a temperature suitable to promote uptake of the markers by the microorganisms. The gel-coated slide irradiated with an external energy source, so as to generate detectable signals emitted from the markers uptaken by the microorganisms. Image of the detectable signals emitted from the microorganisms are acquired, and analyzed using a computer system, in order to provide the identification and enumeration of the microorganisms.