Measurement of fungi by an indirect conductimetric assay

Abstract

Aims: To investigate the growth of fungi using an indirect conductimetric assay and derive, experimentally and theoretically, the relationship between microbial concentration and electrical conductivity change. Methods and Results: The indirect assay, in which change in electrical conductivity of an alkaline solution (NaOH) is produced by absorption of CO2 from microbial metabolism, was conducted with the Bactometer (bioMerieux, Marcy-l'Etoile, France) for the enumeration of fungi. A linear relationship was obtained between detection time and logarithmic initial microbial concentration. This indirect assay used growth media, which could not be used in the direct conductimetric assay, to monitor fungal growth. Conclusions: The indirect assay does not depend on the growth media and the turbidity of sample and could offer a simple and rapid assay for the measurement of fungal growth under various conditions. Significance and Impact of the Study: The indirect assay is applicable for rapid detection of fungi, estimation of the growth rate and evaluation of antifungal activity.