USE OF A UREASE TEST FOR THE SCREENING AND IDENTIFICATION OF CRYPTOCOCCI

Abstract

The increase in mycological work by diagnostic laboratories has stimulated the development of simple and reliable procedures for routine screening and identification of fungus cultures. The writer has investigated the possibility of applying procedures for the diagnosis of yeasts other than the widely used sugar fermentation and assimilation tests. During earlier investigations it was found that capsulated and red pigment-producing yeasts hydrolyzed urea in Christensen's medium (Christensen, 1946) while candida strains and saccharomycetes did not. Therefore studies were initiated to determine whether urea hydrolysis could be used with advantage in routine mycological work. For this study yeast cultures were procured from several recognized laboratories. The results of the examinations were finally compared with a collection of strains at the Communicable Disease Center. Since the findings at both laboratories were in complete agreement and since the urease test offered improvement for the routine identification of yeasts and some yeast-like organisms, the results are given here. For the sake of completeness this report will also present the results with a number of yeasts from Dr. Wickerham's collection which were tested after the writer's return to Germany. MATERIAL AND METHODS Fungus strains. The number of strains of each species used is presented in table 1. All strains were checked for purity and for typical fermentation reaction in 1.0 per cent peptone-water containing 0.5 per cent sodium chloride, and one per cent of the Seitz-filtered sugar solution and bromthymol blue as indicator. Gas production was read after two and seven days in Durham tubes. I Temporarily assigned to