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We determined differences in the expression of certain virulence factors between oral Candida dubliniensis and Candida albicans species. In addition, clonal differences were sought among C. albicans isolates recovered from patients with and without compromised immune system. The material comprised 93 clinical yeast isolates originated in 40 subjects (1-5 isolates per subject). All 26 C. dubliniensis isolates and 46 C. albicans isolates originated from healthy routine dental clinic patients. Additionally, 21 C. albicans isolates were collected from patients with autoimmune polyendocrinopathy-candidosis-ectodermal dystrophy (APECED), who have chronic candidosis as one manifestation of their immunocompromising disease. Polymerase chain reaction amplification using the random sequence primer OPE-03 enabled grouping of the C. dubliniensis isolates in 2 genotypes (I and II) and C. albicans isolates in 15 genotypes (I-XV). No significant difference was found in the distribution of genotypes between the patients with APECED and the healthy subjects. C. dubliniensis isolates exhibited high-frequency phenotypic switching significantly more frequently than did C. albicans isolates, and vice versa regarding phospholipase and proteinase production. Proteinase production was significantly more frequent among C. albicans genotype V than genotype IX isolates. No significant difference was found in expression of virulence factors of C. albicans isolates between the patients with APECED and the healthy subjects.

A total of 4-22 isolates of oral yeasts per subjects from 48 yeast-positive Finnish and American subjects (25 females and 23 males) were phenotyped and genotyped to determine the frequency of simultaneous oral carriage of multiple yeast taxa. An oral sample from either periodontal pockets, oral mucosa or saliva was obtained. All subjects yielded Candida albicans and 3 subjects an additional yeast species (Candida krusei, Candida glabrata or Saccharomyces cerevisiae). The API 20C Aux kit distinguished 9 different carbohydrate assimilation profiles among the C. albicans isolates. Thirty-eight of 46 C. albicans biotype I isolates were categorized in a single numerical profile. PCR analysis, using a random primer OPA-03 and a repetitive primer (GACA)4, detected 2 major genotypic groups among the C. albicans isolates; 44 subjects showing isolates with a "typical" PCR-profile and 4 subjects isolates with an "atypical" PCR-profile. The "atypical" PCR-profile was similar to that of Candida dubliniensis. All C. albicans isolates assimilated xylose, except 5, including the 4 with an "atypical" PCR-profile. No difference was found in distribution of oral yeast species, and of C. albicans phenotypes and genotypes between Finnish and American subjects. The present PCR method may offer a rapid and easy means of distinguishing oral Candida species.

Clonal diversity of subgingival yeast strains was determined in relation to geographical location and coexistence of selected periodontal pathogenic bacteria. A total of 60 dental patients from Finland, the United States and Turkey each contributed five Candida albicans isolates. C. albicans isolates were serotyped using slide agglutination and genotyped using polymerase chain reaction (PCR) amplification and a random sequence primer. In general, each study subject yielded C. albicans isolates belonging to the same serotype and genotype. C. albicans serotype A occurred more frequently in subjects from Finland and Turkey than in subjects from the United States. A total of 27 PCR-based C. albicans genotypes were identified. One C. albicans genotype occurred with particularly high frequency in subjects from Turkey and another genotype in subjects from the United States. Relationships were identified between C. albicans serotypes and genotypes. Further studies are needed to determine environmental factors of importance for subgingival colonization and persistence of C. albicans.

The occurrence and stability of colonization of oral yeast species and strains was determined from 40 healthy children during a 22-month follow-up at the ages 2, 6, 12, 18 and 24 months. In addition, salivary samples were obtained from the mothers at baseline (2 months) to study the role of the mother as the source of yeasts for the child. Yeasts were recovered at least once from 17/40 (43%) children by the age of 2 years. Of the 40 children, 11 (28%) were yeast-positive at multiple sampling occasions. No significant differences were found in recovery frequency of yeasts at different ages. Candida parapsilosis was isolated in 18/33 (55%) yeast-positive samples, and it predominated (share of positive findings 76%) at ages 12 to 24 months. The same yeast species was rarely detected in successive follow-up samples and thus on species level yeasts were transient colonizers in the developing oral flora of the children. Of the mothers 20/40 (50%) harbored yeasts. Candida albicans was recovered from 19/20 (95%) of the yeast-positive mothers and C. parapsilosis from none. Only 7/20 (35%) of the mothers with a yeast-positive finding had a yeast-positive child. In 5/7 (71%) of these mother-child pairs, both harbored the same yeast species (C. albicans) and in 3/5 (60%) of the pairs the AP-PCR profiles of the yeast isolates were identical suggesting possible transmission. In children, significant relationships (Fisher's exact-test, P < 0.05) were found between recovery of yeasts and use of pacifier at age over 12 months, eruption of first teeth at age over 6 months, mother cooling the child's food by blowing and mother cleaning the child's pacifier in her own mouth. In mothers, a significant relationship existed between recovery of yeasts and use of antibiotics.

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