Oral Candida albicans isolates from nonhospitalized normal carriers, immunocompetent hospitalized patients, and immunocompromised patients with or without acquired immunodeficiency syndrome.

A total of 128 human oral isolates of Candida albicans were collected from asymptomatic healthy carriers (64 isolates); asymptomatic, nonimmunosuppressed, hospitalized patients (25 isolates); immunosuppressed transplant patients (19 isolates); and human immunodeficiency virus-infected patients with symptoms of acquired immunodeficiency syndrome and oral candidiasis (20 isolates). Isolates were serotyped as A or B and tested for reactivity with an agglutinating immunoglobulin M monoclonal antibody (H9). Immunocompetent individuals colonized by oral C. albicans were almost equally likely to carry serotype A as serotype B cells, while immunocompromised individuals were at least twice as likely to be infected by serotype B than serotype A strains. The reactivity of isolates with H9 antibody followed a similar but more distinctive pattern. Approximately half of the strains from immunocompetent individuals reacted strongly with H9, and the remainder reacted weakly. However, up to 75% of the isolates from immunocompromised patients reacted weakly with H9, while the remainder reacted strongly. A correlation between H9 reactivity and the serotypes of these isolates existed (P = 0.16). The correlation between H9 reactivity and immune status was even stronger (P = 0.025). The monoclonal antibody activities described above were determined by agglutination tests during defined phases of C. albicans growth. Expression of antigen at various times during growth of several isolates was confirmed at the cellular level by analysis using fluorescence-activated cell sorting. Despite the correlation between serotype A and H9 reactivity, H9 antigen was not identical to the serotype A antigen because four serotype A strains reacted only weakly with H9 antibody, and one strain reacted strongly with H9 but was serotype B. These data indicate that oral strains of C. albicans from immunocompetent individuals differ as a group from C. albicans isolated from those who are immunosuppressed.