A simple system for the presumptive identification of Candida albicans and differentiation of strains within the species

Abstract

A system of 10 agar plate tests allowed presumptive identification of Candida albicans and differentiation of up to 512 strain types within the species. The yeast isolates were tested for acid and salt tolerance, proteinase production, resistance to 5-fluorocytosine and safranine, and assimilation of urea, sorbose, citrate and glycine. Media were inoculated semiquantitatively with a multiple-pronged device so that 55 yeasts and 5 reference strains could be printed on each plate at once. The results for the 9 strain differentiation tests were arranged in 3 groups to allow simple designation of types by 3-digit numbers. Mouth and vaginal samples from 85 patients and healthy volunteers yielded to 45 different strain types, of which types 153, 157 and 357 were the most prevalent. The reproducibility of the system was good, if attention was paid to the precision which the media were prepared and inoculated. The effect of test variables, including incubation temperature, medium pH and inoculum size, was assessed. Work is presently in progress to extend the system for presumptive identification of other clinically important Candida spp. and differentiation of their strain types.