Abstract
Objective: The overall objective of this project was to investigate oral Candida carriage and antifungal susceptibility of Candida albicans isolates in patients receiving antipsychotic medications. Specific objectives were: to determine the level of colonisation with Candida of the oral mucosa in individuals taking antipsychotic medications relative to healthy controls and to xerostomic individuals not prescribed with antipsychotics; to determine the Candida species present; to measure the azole resistance of these isolates; and to determine whether the antipsychotic medication fluphenazine affected azole resistance of C. albicans isolates.
Methods: Nine participants aged between 20 and 70, who were currently on antipsychotic medications were recruited into this study with informed consent. Xerostomia symptoms were determined from the Xerostomia Inventory (XI) and clinical examinations. Saliva rinses were collected by asking each participant to rinse their mouth with 10 mL water for 30 s and then expectorated into specimen bottles. Smears were taken from the buccal mucosa (both sides), tongue, and any other mucosal site with signs of infection. Smears were sent to Medlab for Candida hyphae and yeast identification. Saliva samples were diluted and cultured on CHROMagar Candida™ plates. The colony-forming units (CFU) and species (presumptively assigned from the colony colour) were recorded. The susceptibility of the C. albicans isolates to fluconazole was measured using the E-test and liquid microdilution assay. The interaction between fluconazole and fluphenazine was investigated using a disc diffusion assay and checkerboard liquid microdilution assay.
Results: The majority of the participants (78%) presented with dry mouth. However, the degree of dry mouth symptoms they experienced was not severe based on their XI scores. Four of nine participants (44%) were diagnosed with oral candidosis. The infection coincided with antipsychotic medication intake, although may not have been caused by the antipsychotic because three of the four participants were on other medications as well. Higher numbers of participants were colonised with Candida spp. (7 of 9) compared to an age-matched group of healthy individuals (2 of 9). The numbers of yeast detected per participant was also significantly higher than for the control group. The Candida species most frequently presumptively identified by colony colour on CHROMagar Candida™ was C. albicans. Fluphenazine showed low antifungal activity. However, fluphenazine was found to produce antagonistic effects towards fluconazole, both in disc diffusion assays and the more quantitative checkerboard MIC assays.
Conclusion: Many antipsychotic medications are known to cause xerostomia and predispose to Candida infections. Investigating C. albicans infections and their resistance to fluconazole will potentially lead to more appropriate treatment. The discovery that antagonism between the antipsychotic fluphenazine and fluconazole occurs with C. albicans clinical isolates indicates that careful consideration is necessary when prescribing fluconazole to patients currently taking fluphenazine or medications of a similar class. Other antifungal agents such as nystatin lozenges (not readily available in New Zealand) and amphotericin B lozenges might be better for individuals on such antipsychotic medications.