Abstract:
Objectives: The aim was to investigate the relationship between groups of bacteria identified by cluster analysis
of the DGGE fingerprints and the amounts and diversity of yeast present.
Methods: Bacterial and yeast populations in saliva samples from 24 adults were analysed using denaturing
gradient gel electrophoresis (DGGE) of the bacteria present and by yeast culture.
Results: Eubacterial DGGE banding patterns showed considerable variation between individuals. Seventy one
different amplicon bands were detected, the band number per saliva sample ranged from 21 to 39
(mean ± SD=29.3 ± 4.9). Cluster and principal component analysis of the bacterial DGGE patterns yielded
three major clusters containing 20 of the samples. Seventeen of the 24 (71%) saliva samples were yeast positive
with concentrations up to 103 cfu/mL. Candida albicans was the predominant species in saliva samples although
six other yeast species, including Candida dubliniensis, Candida tropicalis, Candida krusei, Candida guilliermondii,
Candida rugosa and Saccharomyces cerevisiae, were identified. The presence, concentration, and species of yeast in
samples showed no clear relationship to the bacterial clusters.
Conclusion: Despite indications of in vitro bacteria-yeast interactions, there was a lack of association between the
presence, identity and diversity of yeasts and the bacterial DGGE fingerprint clusters in saliva. This suggests
significant ecological individual-specificity of these associations in highly complex in vivo oral biofilm systems
under normal oral conditions.
