Antimicrobial Susceptibility Studies with Varioskan®

Kari Kreander (M.Sc., microbiol.), Laura Riihimäki (M.Sc., pharm.) and Pia Vuorela (Ph.D., pharm.), Viikki Drug Discovery Technology Center, Faculty of Pharmacy, University of Helsinki, Finland

Abstract

Successful discovery of novel natural product antimicrobials has necessitated the development of new bioassay techniques and protocols that allow the detection of small amounts of biologically active chemicals, which should be selective enough to determine optimum target pathogens (Ranta et al., 2000, Ojala et al., 2000, Fyhrquist et al., 2002). For fast screening of new active compounds, microplate method has shown to be the best technique (e.g. Eloff 1998).

In 96 well cell based method the antimicrobial effect of studied compound can be measured as function of time using optical density measurements (Skyttä and Mattila-Sandholm, 1991). However, condensation of water onto the microplate lid has caused difficulties in continuous measurements. This article shows that when Thermo Varioskan is used, it is possible to make long time measurements as the instrument heat the lid to the slightly higher temperature than the other parts of the plate thus avoiding condensation.