A novel procedure for the quantification of antifungal activity against filamentous fungi, mycelial invasion distance (MID) method

A novel method for the quantification of antifungal activity of fungicides and painted surfaces, mycelial invasion distance (MID) method, was developed and applied to the quantification of activities of parabens and an antifungal paint. In this method, the MID of aerial mycelia on a test paper or a panel placed on a nutrient agar plate was measured with a stereoscopic microscope and a micro -ruler. The antifungal activities of the parabens and painted surfaces were expressed as the MID. The higher the hydrophobicity of parabens, the longer the MID, that is the lower the antifungal activity, were observed. Conversely, relatively polar parabens, such as methyl and ethyl parabens, exhibited stronger antifungal activity, that is shorter MID. The most hydrophobic paraben, benzyl paraben, showed the weakest antifungal activity. Furthermore, it was confirmed that the MID method was effective for the evaluation of the painted surfaces.