The inhibitory effect of serum on the growth of Torulopsis glabrata

Normal human plasma and serum were found to inhibit the growth of Torulopsis glabrata and, to a lesser extent, other yeasts. The factor responsible for the inhibition of T. glabrata was not dialysable, was heat stable at 56 degrees C for up to 4 h and could be partly removed by absorption with viable T. glabrata but not Candida albicans. It was fungistatic at low concentrations and fungicidal at high concentrations, stable up to 4 years between -20 degrees C and -70 degrees C, but for only a few weeks at 4 degrees C. Studies with Cohn fractions of serum showed that the inhibitory components were in either the alpha or beta globulin fraction or both. The combined effects of transferrin and IgM accounted for about 70% of the total inhibition observed. We were unable to identify the component responsible for the residual inhibition of growth. The inhibitory effect was totally neutralised by tetracyclines, quinolones, sulphamethoxazole and by very low concentrations of polyenes, imidazoles and 5-fluorocytosine.