The use of epifluorescence microscopy to determine surface hygiene

Abstract

Within the food industry a need has been established for rapid techniques to assess the microbial contamination on food contact surfaces. A method was developed, by adapting the DEFT technique, to stain and enumerate microorganisms by direct epifluorescent microscopy. The method was evaluated by developing biofilms of various organism on a range of food grade surfaces, and in factory environments using test sampling plates. Cleaning trials were undertaken to examine the ability of the method to detect low levels of surface contamination. The method was shown to enumerate surface organisms rapidly (⩽15 min) within the range 3 × 10 3−5 × 10 7 colonies/cm 2. No difficulties were experienced in evaluating different organisms nor the majority of food grade surfaces. The technique may prove useful in allowing a real-time control for the assessment of surface hygiene.