The effect of temperature, pH and medium in a surface adhesion immunofluorescent technique for detection of Listeria monocytogenes.

A rapid surface adhesion-based immunofluorescence technique was used to detect Listeria monocytogenes from inoculated culture systems. The effect of culture type (pure, mixed and meat), pH (7.00, 6.40, 4.76 and 3.13), acids (citric and HCl) and temperature (25 degrees, 30 degrees and 37 degrees C) on the adhesion of Listeria to the polycarbonate membrane used in this technique was determined. It was found that pH had a significant effect (P < 0.05) with higher numbers of Listeria adhering at low pH values (4.76). Culture type was also important with significantly higher numbers of Listeria (P < 0.05) adhering to membranes immersed in meat cultures than in pure or mixed cultures. This effect was seen at 30 degrees C but not at 25 degrees or 37 degrees C. The total viable count (TVC) on the membrane was unaffected by pH but temperature had an influence with optimum adhesion occurring at 25 degrees C. The reasons for observed differences and their implications for the surface adhesion immunofluorescent rapid method are discussed.