For the early diagnosis of systemic candidiasis which has been increasing in recent years, we developed an enzyme-linked immunosorbent assay with avidin-biotin system (A-B ELISA) to detect serum Candida antigen. A-B ELISA was evaluated in murine systemic candidiasis.
A-B ELISA detected purified C. albicans mannan with a sensitivity of 1.2 ng/ml inpooled human sera, and 0.25 ng/ml in PBS. Except for C. tropicalis C. guilliermondii and C. stellatoidea, no cross reactivities were seen with a variety of other fungal and bacterial antigen preparations. Anti C. albicans antibody which was used in this method was shown a specific binding to purified Candida mannan by ELISA inhibition technique.
In experimental systemic candidiasis of mice, serum Candida antigen was positive in 14 of 26 mice, but blood culutre was negative except for one. There was a relationship between serum antigen concentration and an area of abscesses in renal cortex and total organs of infected mouse. On the other hand, even if the foci had developed in large area, Candida antigen was not detected when the lesion had been transformed from abscess to granuloma. Therefore it is important for the diagnosis of systemic candidasis when the sample should be taken.
These results suggest that A-B ELISA to detect Candida mannan antigen is an useful method for diagnosis of systemic candidiasis because of its simple and timesaving feature and high sensitivity.