Oral Yeast Carriage and Salivary Protein Profiles in Xerostomia Subjects and in Age- and Gender-Matched Controls

Abstract

Aims: To investigate if there is a significant association between increased oral colonisation by yeast species, such as C. albicans, and a sensation of dry mouth, and if there is a difference in the saliva proteins detected in xerostomia subjects from those in age- and gender-matched controls.

Methods: This was a cross-sectional study (ethical approval: LRS/10/09/034) in which oral yeast carriage and saliva proteins were investigated in saliva rinse samples. Mouth rinses (10 ml bottled water for 30 s) were obtained from 20 individuals attending Oral Medicine clinics; inclusion criteria included self-reported dry mouth. Samples were also obtained from 20 age- and gender-matched controls. Study participants completed a medical questionnaire. Yeast numbers and species were presumptively identified using chromogenic agar plates (CHROMagarTM Candida). Saliva samples were subjected to SDS-PAGE analysis of protein content. Salivary proteins were visualized by two staining techniques; a Coomassie Blue-based commercial stain (EZBlueTM) and the more sensitive silver stain. Protein profiles were analyzed and compared both by visual comparison to an internal standard and by using an automated image analysis system (Gel DocTM EZ).

Results: Examination of the patient data revealed that there were several possible causes of the self-reported dry mouth including use of medications linked to xerostomia and denture wearing. Sixteen of the 20 dry mouth patient had a salivary flow rate ≤ 0.1 ml/min. Five patients met the criteria for Sjögren’s syndrome.

The prevalence of yeasts in saliva samples from individuals reporting a dry mouth was significantly greater (p < 0.05) than in control samples. There was also a greater number of yeast species and a greater total number of yeast cells in the xerostomia saliva samples. Interestingly, although 18/20 xerostomia subjects were colonised by yeast presumptively identified as C. albicans six of these subjects were also colonised by a yeast presumptive identification as Candida glabrata. C. glabrata is an emerging opportunistic pathogen, which shows inherent resistance to the azole class of antifungal drugs. There was a weak negative correlation between the number of yeast present in the rinse sample and the saliva flow rate for xerostomia subjects.

Protein profile analysis confirmed the utility of an automated image analysis system. Although the system allowed rapid comparison of gels and determination of the molecular weights of individual proteins, it had less sensitivity than use of a non-automatic digital camera and visual analysis of images. However, neither method revealed any consistent differences between the salivary protein profiles of the two subject groups.

Conclusions: The study showed that oral colonisation by yeasts in individuals with xerostomia occurred at a greater frequency than in healthy individuals and thus individuals with xerostomia may be more susceptible to oral yeast infections. No significant differences in the salivary protein profiles of xerostomia subjects and healthy controls were observed, and therefore it was not possible to determine whether salivary protein changes could be responsible for the increased prevalence of oral yeast colonisation in individuals with xerostomia. However, the study showed that factors other than low saliva flow may contribute to increased oral yeast colonisation in such individuals.

This project was supported by a University of Otago Faculty of Dentistry Fuller scholarship.