Model system for the in vitro testing of a synthetic histidine peptide against Candida species grown directly on the denture surface of patients with denture stomatitis.

The denture surface provides a nidus for the growth of microbial species that act to initiate, aggravate, and maintain clinical disease. The present investigation describes the development of a model system for the testing of the effectiveness of agents against these microbial species inhabiting the denture surface. It was observed through in vitro growth patterns that the model permitted the testing of representative samples of the microbial flora. Poly-L-histidine was observed to inhibit both Candida albicans and C. glabrata from growing from the denture surface into nutrient broth. Scanning electron microscopy of control and treated denture disks revealed that poly-L-histidine had either eliminated most microbial flora from the denture surface or had effected a noticeable distortion of those Candida blastospores still present on the surface. From microbiologic studies, it appeared that poly-L-histidine had inflicted direct but not lethal damage to the still-attached distorted blastospores because the latter were still able to promote growth in agent-free broth. The antifungal effects of poly-L-histidine were observed to be dependent on the concentration of the polypeptide. The data obtained were consistent for all of the patients regardless of their denture stomatitis classification.