Oral Candida albicans from patients infected with the human immunodeficiency virus and characterization of a genetically distinct subgroup of Candida albicans

Candida albicans has been shown to vary in its phenotypic expression with the progression of human immunodeficiency virus (HIV) infection. This study was designed to investigate whether in Category IV HIV infected patients (CDC, Atlanta, USA) these phenotypic changes were related to changes in the genetic strain of the organism. Isolates of C. albicans were obtained from 45 patients with HIV infection during the progression of their disease as determined by percentage T4 lymphocyte count. Isolates were strain differentiated using two methods. In 67 per cent of the patients a single strain of C. albicans, as determined by the DNA analysis, was isolated from each individual over the experimental period. The phenotypic expression of the genetically identical strains isolated from each patient varied considerably over the experimental period with the morphotype 754 being predominant. These results showed that the genotype of C. albicans isolated persisted in the majority of HIV infected individuals, but that the phenotypical expression of this strain changed. A finding in this study was that 18 strains of C. albicans had DNA which did not hybridize to the probe used. These strains were analysed for the presence of two other C. albicans specific DNA segments using PCR. The probe 27A hybridizing strains yielded PCR products which differed from the non-hybridizing strains. Five of these genetically atypical C. albicans strains and 98 of the C. albicans strains were then analysed for purported virulence factors. The genetically atypical C. albicans strains, by comparison with typical C. albicans strains, produced greater amounts of extracellular proteinase (p = 0.038, Student's t test), adhered to a greater degree to buccal epithelial cells (p = 0.018, Student's nest) and were less susceptible to the anti-fungal drug flucytosine (p = 0.0003, Mann-Whitney test). Analysis of these strains with other common antifungal drugs showed no statistically significant variation in susceptibility. The results of this study indicated that these genetically atypical C. albicans strains possess increased virulence by comparison with typical C. albicans strains.