1999

Wirtanen, Gun; Salo, Satu; Mattila-Sandholm, Tiina

Cleaning procedures with or without disinfectant treatment for both open and closed systems were used in developing an assessment system based on various microbial methods for detection of residual surface-attached microbes and soil on surfaces after sanitation. The microbial methods tested were cultivation, microscopy using image analysis after staining with acridine orange, viability staining, impedance measurements, viable counts with TTC agar and ATP measurements. Conventional cultivation, combined with impedance measurements and image analysis of surfaces stained with acridine orange gave results that were comparable and complementary. Combination of these methods enabled a total evaluation of both the removal of biofilm and the killing of bacterial cells. Some of the cleaning procedures tested neither removed all of the bacterial cells from the surfaces nor killed the bacteria. The above-mentioned testing protocol can also be used for evaluating the sensitivity of microbial testing methods for use in certain industrial premises.