Antibodies against antigens of Candida albicans in patients with fungaemia and bacteraemia, studied by ELISA, precipitation, passive haemagglutination and immunofluorescence techniques.

Antibodies against commercially available antigens of Candida albicans were assayed in 54 sera from 24 patients with fungaemia and in 66 sera from 33 patients with bacteraemia. In patients with persistent fungaemia, antibody was found during the week after the fungus was first cultured from the blood, but peak titres did not usually occur until the end of the second week. A significant rise in titre in C. albicans infection was observed in 50% of paired sera tested by passive haemagglutination (PHA), indirect immunofluorescence (IF) and Ouchterlony immunodiffusion (ID). The same percentage was obtained by counterimmunoelectrophoresis (CIE) against candida metabolic antigens, whereas it was increased to 88% when somatic antigens were used. Enzyme-linked immunosorbent assay (ELISA) demonstrated a rise of titre in 25, 75 and 50% of sera in IgM, IgG and IgA assays, respectively. Sera from patients with transient fungaemia demonstrated persistent antibody titres. In paired sera from patients with bacteraemia, ID and CIE titres were low (greater than or equal to 4). There was an increase of candida antibodies in 0-9% of patients by ELISA, ID or CIE and in 18-21% by PHA or IF. Clinically significant fungaemia was most reliably differentiated serologically from bacteraemia by CIE S-antigen and ELISA IgG assays.