Proteolytic activity of clinical Candida albicans isolates in relation to genotype and strain source

Proteolytic activity is regarded as one of the most important virulence factors of Candida albicans. Several authors recently demonstrated that some karyotypes and genotypes harbouring a group I self-splicing intron (CaLSU) located in the gene encoding the large rRNA subunit showed a high level of proteinase production. The aim of this study was to investigate the correlation between the level of proteinase production and the presence of the CaLSU intron in C. albicans isolates originating from the blood and respiratory tracts (sputum/pharyngeal swabs) of patients with and without oropharyngeal candidosis. The results revealed statistically significant differences in genotype distribution and the level of proteinase production between the C. albicans isolates obtained from blood and from the respiratory tract. Genotype A, without the intron, was prevalent in all groups of strains and its prevalence was higher among isolates from blood (75%) and from patients with candidosis (80%) compared with strains from colonisation (as opposed to infection) (57.8%). Isolates from blood produced significantly less proteinase than isolates from the respiratory tract (p<0.02), and this difference should be attributed to lower proteinase production of genotypes B and C from blood compared with genotypes B and C from the respiratory tract (p<0.01). The higher proteinase production of genotype B than of genotype A was found among respiratory tract isolates only. The presented data indicate that the association between proteinase production and the CaLSU intron depends on the strains' population. Further study is needed on well-defined groups of clinical isolates to elucidate whether the observed diversity in proteinase production plays a role in the selection of strains inducing bloodstream infections.