Quantitative assay of (1-3)-beta-D-glucan in culture media of Candida albicans using the G-test.

The diagnosis of invasive candidiasis is often difficult. The limulus test, which has been used for the assay of endotoxin in blood, was also found to react with (1-3)-beta-D-glucan, a component of the fungal cell wall. The factor in the limulus test that is activated by glucan, but not by endotoxin, is called factor G. The G-test utilizes the activation pathway starting with factor G, and sensitivity reacts with trace amounts of glucan. In this study, we investigated in vitro proliferation of Candida albicans and changes in the glucan concentration of RPMI-1640 media in the presence and absence of neutrophils and antifungal agents, as a pilot evaluation to possible clinical applications of the G-test. The proliferation of C. albicans and the glucan level measured in the culture media showed parallel changes. The glucan level in the culture media also increased when C. albicans was phagocytosed and digested by neutrophils, but not with administration of amphotericin B. The G-test closely reflected quantitative changes of C. albicans in vitro, and should be considered for future clinical studies in the diagnosis and evaluation of therapeutics in invasive candidiasis.