IMPROVED DETECTION OF BACTERIA BY FLOW-CYTOMETRY USING A COMBINATION OF ANTIBODY AND VIABILITY MARKERS

A proprietary fluorogenic marker for cell viability (Chemchrome) was i nvestigated for the detection of bacteria using flow cytometry. This m arker was used in combination with fluorescently labelled monoclonal a ntibodies (against Salmonella typhimurium). Owing to the former's broa d band emission spectrum, it was necessary to use the novel dye RED613 for the antibodies. This combined protocol, being sensitive only to t he live Salm. typhimurium cells, reduced errors due to intrinsic fluor escence and non-specific binding. Detection of the order of 100 cells ml(-1) was achieved in 30 min. This level was achieved even in the pre sence of large numbers of non-target or dead organisms.