Fractional inhibitory concentration

Fractional inhibitory concentration (FIC) values were calculated to determine whether a synergistic or additive effect was exhibited as a result of a combination of fragrances that showed antibacterial or antifungal activities. FIC values were calculated with the equations described below [21].

After the FIC values were calculated, the fractional inhibitory concentration index (FIC_Index) was calculated as follows:

Since FIC_Index is calculated based on the MIC of each fragrance in the mixture. A FIC_Index <1.0, 1.0 or >1.0 was defined as the synergistic, additive or antagonistic effect of the fragrance combinations, respectively [22].