Effect of pH and Iron Concentration on Growth of Candida albicans in Human Serum

The in-vitro growth of Candida albicans in serum is markedly inhibited compared with its growth in Sabouraud's broth. The effect of pH and concentration of iron on the ability of C. albicans to grow on these two media was studied. The growth of C. albicans in human sera is inversely proportional to the pH and directly related to the percentage of iron saturation in the serum. A possible mechanism for the observed linear growth rate of Candida in serum with reduction in pH is a concomitant change in the ability of the transferrin molecule to bind iron. The growth-promoting capacity of human serum can be made commensurate with that of Sabouraud's broth by lowering the pH to 6.3 or by adding iron in excess of the total capacity to bind iron. Thus, it is imperative to evaluate the pH and percentage of iron saturation when studying growth of Candida in serum.