Role of yeasts in the salivary acetaldehyde production from ethanol among risk groups for ethanol-associated oral cavity cancer

Background: Acetaldehyde, the first metabolite of alcohol, has been propose d to be the carcinogenic substance behind ethanol-related oral cancers. Hig h levels of acetaldehyde are formed from ethanol in saliva by the oral nora , but so far the role of certain microbial species responsible for this phe nomenon is not known. Yeasts are common commensals of the oral cavity that have alcohol-oxidizing enzymes, thus providing a potential source of acetal dehyde from ethanol. The aim of this study was to examine the contribution of oral yeasts to the production of ethanol-derived acetaldehyde in the ora l cavity. Methods: Fifty-five saliva samples were divided into Two groups, high and l ow, based on the in vitro salivary acetaldehyde production capacity from et hanol. Yeasts were isolated and identified from these samples, and their ac etaldehyde production capacity was determined gas chromatographically by in cubating intact cells with ethanol at the physiological pH of 7.4. Results: Yeast colonization was found in 78% of the high acetaldehyde-produ cing salivas, compared with 47% in the low acetaldehyde-producing salivas ( p = 0.026). Among carriers, the density of yeasts was higher in the high th an in low acetaldehyde producers (p = 0.025). Candida albicans was the main species isolated (88% of all oral isolates). Moreover, C. albicans strains isolated from the high acetaldehydeproducing salivas formed significantly higher acetaldehyde levels from ethanol than C. albicans strains from low-a cetaldehyde-producing salivas (73.1 nmol ach/10e6 colony-forming units vs. 43.2 nmol ach/10e6 colony-forming units, p = 0.035). Conclusions: This study shows that some C. albicans strains have a marked c apacity to produce toxic and carcinogenic acetaldehyde from ethanol in vitr o. Because the in vitro production of salivary acetaldehyde has been previo usly shown to correlate with in vivo acetaldehyde production, our finding c ould be an important microbial pathogenetic factor underlying cancer of the oral cavity associated with ethanol drinking.