The adherence of Candida albicans to a fibrin-platelet matrix formed in vitro was studied. Platelet-rich plasma obtained from rabbits was incubated with thrombin and CaCl2 to form a clot in tissue culture dishes. Such clots were then infected with 3 x 107 C. albicans cells per 0.3 ml prelabeled with [U"4C]-glucose, and the percent adherence was measured after 30 min of incubation by counting the radioactivity in saline washes of the clot as well as a streptokinase-streptodornase digest of the corresponding clot. Heatand formaldehyde-killed cells did not adhere as well as viable cells. Pretreatment of C. albicans with trypsin, chymotrypsin, and pronase reduced adherence to the clots. Normal rabbit serum and anti-Candida antiserum also inhibited adherence 40 and 100%, respectively. Diethylaminoethyl-purified anti-Candida gamma globulin (1:8) completely inhibited adherence, whereas purified normal serum gamma globulin did not. Several Candida spp. and Saccharomyces cerevisiae showed differences in their ability to adhere to clots. C. albicans and C. stellatoidea presented the highest adherence, whereas C. krusei, C. guilliermondii, and S. cerevisiae adhered less readily. Other species were intermediate in their ability to adhere.

An alkali-soluble extract from a cell wall preparation of Candida albicans was conjugated to sheep erythrocytes (SRBC) by using periodate oxidation or concanavalin A. Conjugated SRBC readily attached to a fibrin-platelet matrix, whereas nonconjugated SRBC did not. To determine the active component which promoted attachment of SRBC, the alkali-soluble fraction was treated with alpha-mannosidase, pronase, or glusulase or chemically degraded by acetolysis. The treated extract was then reconjugated with SRBC, and attachment was measured. When treated with alpha-mannosidase or degraded by acetolysis, the alkali-soluble extract failed to promote the adherence of SRBC to the fibrin-platelet matrix. Pronase- or glusulase-digested extract promoted attachment equally as well as untreated controls. In addition, when preabsorbed with antiserum to whole cells of C. albicans, the alkali extract abrogated the inhibition of adherence by antiserum, thus indicating its antigenicity. The extract consisted primarily of polysaccharide (72%) and contained a small amount of protein (less than 1%). Mannose and glucose (ratio, 3:1) were detected by gas-liquid chromatography. These data indicate that cell surface mannan may play an important role in the adherence of C. albicans to the fibrin-platelet matrices which form in vivo on the endocardium of heart valves.