A simplified immunofluorescence technique for detection of viable cells of Vibrio cholerae O1 and O139

A direct fluorescent monoclonal antibody staining method has been developed for rapid detection of viable cells of Vibrio cholerae O1 and O139. Microcosm samples containing V. cholerae O1 or O139 serogroup were incubated with yeast extract in the presence of nalidixic acid, after which the viable, substrate-responsive cells became enlarged and elongated. These cells could be readily detected by staining with fluorescein-labeled, serogroup-specific monoclonal antibody. When this procedure is used, viable cells of V. cholerae O1 or O139, depending on the monoclonal antibody employed, appear as elongated rods, with a green fluorescing periphery under the epifluorescent microscope. The method is readily adapted for other gram-negative bacterial species, for which fluorescein-labeled, specific monoclonal antibodies are available.