Seventy-nine isolates of Candida albicans and 33 of 5 other pathogenic species of Candida were cultured for 3 h at 37°C in 1·5% aqueous solution of 6 peptone media. While all isolates of C. albicans formed germ tubes, the other species did not. Some isolates of C. albicans formed germ tubes in 1·5% trypticase peptone and neopeptone, and all did so in phytone, bactopetone, polypeptone and proteose peptone at the same concentration. Subsequently, 140 isolates of C. albicans were inoculated at the rate of 106 organisms/ml into concentrations of bactopeptone from 0·5% to 2·5%, into distilled water and into undiluted sheep serum. The tendency to germ tube formation was greater in 1% than in 0·5% bactopeptone, and in both of these media it was greater than in other concentrations of bactopeptone or whole sheep serum. Germ tube formation also occurred to a very limited extent in distilled water. The significance of these findings is discussed(Joshi et al., 1973).<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
The colonies of 12 isolates of 3 Candida spp. with variant colony forms were studied by scanning and transmission electron microscopy. Small colonies were formed by 4 isolates each of C. albicans and C. parapsilosis and by 1 of C. tropicalis. These had an abnormally high proportion of degenerate yeast cells with an associated increase in granular cytoplasmic material intercellularly. The increased matrix in these small colonies formed a thick superficial coat over the organisms. Rough colonies were formed by 1 isolate each of C. albicans, C. tropicalis and C. parapsilosis. The convoluted regions of these colonies contained many pseudohyphal cells but few degenerate cells and little granular or fibrillar material in their intercellular matrices. The shape of colonies of Candida spp. may be altered by variations in the viability or the morphology of the organisms Joshi and Gavin<?xml:namespace prefix = v ns = "urn:schemas-microsoft-com:vml" /> (1975).
A simple, relatively inexpensive method for distinguishing Candida albicans from other species of the genus Candida was developed. The organisms were first spread on a solid 2% agar medium which contained 1% bactopeptone, then incubated at 37d`C for three hours and finally examined microscopically. A coverslip placed over the organisms at the time of inoculation increased from 93.5 to 100% the proportion of isolates of C. albicans which formed parallel-sided germ tubes when tested in this way. Five other species of Candida (parapsilosis, krusei, tropicalis. pseudotropicalis and guilliermondii) were also tested but did not form germ tubes. Organisms of C. tropicalis sometimes formed elongated buds but these could be readily distinguished on direct microscopic examination from germ tubes by the constriction at their base (Joshi and Gavin 1973).
Eight isolates of C. albicans were used to determine the frequency with which germ tube formation occurred: on rice extract -Tween 80 agar, on its components, and on 1% bactopeptone agar after three hr at 37 degrees C; in 0.5% aqueous solution of various carbohydrates; in various concentrations of glucose; on 0.5 and 0.1% glucose agar and on various types of agar alone. Subsequently 250 isolates of yeast of the genera Candida, Torulopsis, Trichosporon, Cryptococcus, and Saccharomyces, which were obtained from a clinical laboratory, were spread on rice extract -Tween 80 agar and on 0.1% glucose agar and covered with coverslips. Direct microscopic examination after incubation for three hours at 37 degrees C demonstrated germ tube formation by all 140 isolates of C. albicans, but by none of the other yeasts. The characteristic features of the pseudomycelia of isolates of Candida and Trichosporon were evident on reexamination after a further 45 to 69 hours at room temperature (22 degrees C). These morphological observations suggested the identity of the isolates of Torulopsis, Cryptococcus, and Saccharomyces but identified virtually all (98.2%) of those of the genera which formed pseudomycelia. Of the latter group only four isolates required fermentation and assimilation tests to determine whether they were C. parapsilosis or C. guilliermondii . Joshi et al., (1975)
A chemically defined medium composed of 6 amino acids, biotin, inorganic salts and glucose for the growth of yeast and mycelial phases of Candida albicans at 25°C and 37°C respectively was developed based on the aminopeptidase(s) profile of the fungus. This medium has proved successful in maintaining the growth characteristics of both phases during serial transfers. The relative pathogenicity, virulence, invasiveness and immunogenicity of the yeast and mycelial phases are discussed (Lee et al.,1975)
Joshi, K R D A Bremner, D N Parr, J B Gavin (1975)
The morphological identification of pathogenic yeasts using carbohydrate media. Journal of Clinical Pathology; 28:18-24
Joshi, K.R., J.B. Gavin and D.A. Bremner (((1973)
The formation of germ tubes by Candida albicans in various peptone media
Medical Mycology 11: 259-262.
1975, Vol. 13, No. 3, Pages 274-279
Joshi K.R and J.B. Gavin (1975)
The morphology of colony variants of three species of Candida
Medical Mycology 13: 274-279
Joshi , K. R. and J. B. Gavin (1974)
A simple laboratory method for the rapid identification of candida albicans
Pathology 6 : 231-233
Lee K.L., Helen R. Buckley and Charlotte C. Campbell (1975) An amino acid liquid synthetic medium for the development of mycellal and yeast forms of Candida albicans. Medical mycology 13: 148-153.