A membrane-immunofluorescent-viability staining technique for the detection of Salmonella spp. from fresh and processed meat samples

A direct staining technique was investigated for the detection of viable Salmonella in fresh and processed meats. The technique involved overnight enrichment in BPW, extraction of Salmonella cells onto a polycarbonate membrane, followed by detection of the pathogen using anti-Salmonella monoclonal antibody coupled with an antibody linked-fluorescent stain (Texas Red) and a viability stain (Sytox Green). The technique was applied to the detection of Salm. enteritidis inoculated into broth culture or minced beef and then subjected to a variety of stresses including freezing (- 20 degrees C), heating (2 or 4 min at 56.9 degrees C), low pH (5 or 3.5) or high salt (2 or 4%). The correlation between traditional plate counts and the rapid count varied widely (r2 = 0.98-0.03), depending on the type and level of stress applied to the cells. The reason for the disparity in results obtained, and the potential application of the method as a diagnostic tool, are discussed.