An Improved Method for the Screening of Fungal Growth Inhibition

Suzanna J. C. M. Oomes, Stanley Brul

Microbiology and Preservation Unit, Unilever Research, Vlaardingen Laboratory, Olivier van Noortlaan 120, 3133 AT Vlaardingen, the Netherlands

Article history:
Received September 10, 1997
Accepted January 15, 1998

Key words:
antifungal substances, plate reader, screening method, fungi

Summary:
There are different ways to determine the antifungal activity of substances. This can be done by means of the disk method, which is a visual method. There are also automatic systems available. In this paper we describe a method which is based on measuring growth in the form of changes in optical density during the incubation time. The optical density measurements zuere performed with a Mulliskan MCC/340 (Labsystems, Helsinki, Finland). We used 0.375% agar in 20 g/L Malt Extract Broth as end concentration. The wells were filled in total with 225 µL, 75 µL test substance, 75 µL medium with fungal spores, and 75 µL paraffin on lop. If a plate with 96 ivells is filled under the above-mentioned conditions, and placed in the Multiskan MCC/340 with stacker, the test can continue with a maximum of 20 plates without any handling for the duration of the experiment. The data were collected and stored in a computer file which was processed using SAS. The computer software (developed on site) has an option to check the optical density in the form of a graph during the experiment, which allows one to see on-line if a test substance has antifungal activity. The system can also be used as preliminary screening for mode of action experiments.