Oral candida carriage and the antifungal activity of parotid secretion

Abstract

When local or general predisposing factors are present, Candida, an oral opportunistic pathogen, may cause acute or chronic oral infections. It is well known that healthy individuals differ with respect to the carrier status of Candida a/bicans. The aim of this project was to determine Candida carriage among healthy individuals, and to investigate the spectrum of antifungal activity of parotid secretion. To determine the oral Candida carrier status, masticatory stimulated whole saliva (WS) was collected from thirteen healthy subjects, every 2 to 3 days, during a 2 week time interval. The cell sediment from 1 ml WS was suspended in 100 μI phosphate buffered saline (PBS, pH 7.0) and plated on Sabouraud dextrose agar or on Chromagar to determine the number and type of fungi present in WS, respectively. Gustatory stimulated parotid secretions (PS) were collected from four of the thirteen subjects, two being low and two being high Candida carriers. The fungistatic activity of the collected PS secretions was evaluated in growth media assaying 15 medically important fungi including 6 strains of C. albicans. Four of the 13 subjects were found to be non-Candida carriers in WS (zero colonies on all sampling occasions), five were low carriers (zero to a few colonies cultured per occasion) and four were high carriers (never zero colonies, mostly double digit counts). The total number of C. albicans in the carriers showed considerable fluctuation, which was established to be due to the sampling occasion. However, noncarriers maintained their non-carrier status during the entire interval of examination. PS collected from four of the thirteen subjects exhibited a surprising trend of being fungistatic toward many fungal species, as evidenced from the low IC50 values, while being 20-50 fold less active against the six evaluated strains of C. albicans. This was true for PS samples collected from low or high Candida carriers. Considering the fact that PS is a major contributor to oral fluid, this observation would suggest a lower overall antifungal activity in the oral cavity toward C. albicans in particular. It is hypothesized that this may be a contributing factor to the successful oral colonization of C. albicans.