A microbiologic and ultrastructural investigation of germ-tube formation by oral strains of Candida tropicalis.

Presumptive germ tube-positive and -negative Candida tropicalis strains have been obtained from both normal children and patients who have candidiasis. Examination of these strains by conventional microbiologic tests confirmed them to be C. tropicalis. Ultrastructural examination of the filaments produced by the positive strains revealed two types: true germ tubes and those with basally constricted cytoplasm. A fluctuation analysis of the positive strains showed two subgroups: germ tube-positive and -negative. It is suggested that C. tropicalis strains may be divided into germ tube-positive and -negative strains, and that germ-tube formation must therefore not be used as a sole criterion for identification of C. albicans.