Should Solubility and Zone of Inhibition Be the Only Criteria for Selection of Solvent in Antimicrobial Assay?

Effect of different solvents; dimethyl-sulfoxide (DMSO), dimethyl formamide (DMF), methanol, tween 80 and acetone on morphology, cytology and reproduction of Aspergillus flavus, A. parasiticus, A. fumigatus and A. niger was assayed for standardization of a suitable organic solvent for test/antimicrobial compound in antimicrobial assays. Comparison of antimicrobial sensitivity methods was also made. Inhibition of pigmentation, conidia germination and dichotomous branching in conidiophores was observed in all test fungi after treatment with DMSO and DMF. Increased mycelial width, conidia size, conidiophores size was found in presence of tween 80. It was observed that culture was more sensitive to solvents in dilution method as compared to diffusion method. Results showed that standardization of solvents could be achieved through screening their effects on various parameters such as morphology, cytology and reproduction of different organisms preferably prior to assay of antimicrobial properties of a compound.