Activity of antimicrobial peptide fractions of human serum and saliva against clinically important yeasts

Every human bioliquid contains substances possessing direct antimicrobial activity. These substances include complement system proteins of serum, immunoglobulins of serum and epithelial secretions, and antimicrobial peptides/proteins (AMP) with low molecular masses, which are present at all sites and liquids of human body. The aim of this study is to estimate the AMP fraction activity of serum and saliva towards different clinically important yeasts. Specimens of serum and saliva were obtained from 10 healthy volunteers 5 women and 5 men, 20-26 years old. Strains of yeasts Candida albicans, Rhodotorula mucilaginosa, Malassezia furfur, Cryptococcus neoformans, Geotrichum candidum, Trichosporon cutaneum and Saccharomyces cerevisiae were used in the experiments. Native (total) liquids and their AMP fractions obtained by filtration through a membrane of 100 kDa were used in the process of antimicrobial activity estimation carried out by the spectrophotometric method. The AMP activities were 2.3-13.5 fold lower than the corresponding total ones, the yeasts most susceptible to serum AMP were C. albicans and Cr. neoformans. Total salivary antifungal activities were 3.6-5.2 fold lower than the corresponding total serum activities. Total activity of saliva was significantly higher towards R. mucilaginosa, while that of the other ones were almost the same. AMP activities of saliva were 1.1-3.8 fold lower than the total ones. R. mucilaginosa and T. cutaneum were the most sensitive to AMP fraction of saliva. Gender difference with regard to the activity of the studied bioliquids was also observed: the most significant ratio was obtained for the sensitivity of C. albicans to women/men salivary AMP. Based on the above data one can conclude that among the studied yeast genera/species show specificity to AMP. It is expressed in terms of the varying sensitivity of the yeasts to the AMP fraction in serum and saliva.