A comparison of the activity of mepartricin and amphotericin B against yeasts.

An in-vitro comparison was made of the activity of mepartricin and amphotericin B against yeasts both in the presence and absence of pooled human plasma. The methods used included minimum inhibitory concentrations (MICs), liquid cultures and scanning electron microscopy (SEM). Mepartricin was found to be consistently more active than amphotericin B and to exhibit a partial inhibitory action over a wider range of concentrations below the MIC. In the presence of plasma, amphotericin B had increased activity but there was a slight reduction for mepartricin. By electron microscopy both drugs exhibited a rapid effect on Candida albicans and the cell membrane was found to be their primary target. Mepartricin was found to have the additional effect of causing a delayed separation of dividing cells and damage on both sides of the septum between mother and daughter cells. This suggests interference with the enzymatic mechanism of septum formation or chitin synthesis.