Rapid enumeration of viable micro-organisms by staining and direct microscopy

Abstract

A rapid method is described that uses the tetrazolium salt 2-(p-iodophenyl-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (INT) to stain viable micro-organisms retained on a filter membrane. Good correlation exists between numbers of INT stained cells and aerobic plate counts of single strain cultures of bacteria and yeasts. A pre-treatment step allows the technique to be used for pasteurized milk.