Oral colonization by Candida albicans

Candida albicans is a commensal yeast normally present in small numbers in the oral flora of a large proportion of humans. Colonization of the oral ca vity by C. albicans involves the acquisition and maintenance of a stable ye ast population. Micro-organisms are continually being removed from the oral cavity by host clearance mechanisms, and so, in order to survive and inhab it this eco-system, C. albicans cells have to adhere and replicate. The ora l cavity presents many niches for C. albicans colonization, and the yeast i s able to adhere to a plethora of ligands. These include epithelial and bac terial cell-surface molecules, extracellular matrix proteins, and dental ac rylic. In addition, saliva molecules, including basic proline-rich proteins , adsorbed to many oral surfaces promote C. albicans adherence. Several adh esins present in the C. albicans cell wall have now been partially characte rized. Adherence involves lectin, protein-protein, and hydrophobic interact ions. As C. albicans cells evade host defenses and colonize new environment s by penetrating tissues, they are exposed to new adherence receptors and r espond by expressing alternative adhesins. The relatively small number of c ommensal Candida cells in the oral flora raises the possibility that strate gies can be devised to prevent oral colonization and infection. However, th e variety of oral niches and the complex adherence mechanisms of the yeast mean that such a goal will remain elusive until more is known about the con tribution of each mechanism to colonization.