Germ Tube Test For Candida albicans

image courtesy of: www.openi.nlm.nih.gov

Principle:
Strains of C. albicans produce germ tubes from their yeast cells when placed in a liquid nutrient environment and incubated at 35 degree Celsius for 3 hours (similar to the in vivo state).

Method:
1. Suspend a very small inoculum of yeast cells obtained from an isolated colony in 0.5 ml of sheep serum, human serum or rabbit plasma.
2. Incubate the tubes at 35 to 37 degree Celsius for no longer than 3 hours.
3. After incubation, remove a drop of the suspension and place on a microscope slide. Examine under low- power magnification (LPO)/ high- power magnification (HPO) for the presence of germ tubes. A germ tube is defines as an appendage that is half the width and 3 to 4 times the length of the yeast cells from which it arises. In most instances, there is no point constriction at the origin of the germ tube from the cell. (see image above)

Quality Control:
C. albicans and C. tropicalis are used as positive and negative controls, respectively.

Expected Results:
C. albicans will produce germ tubes, usually within 2 hours, while C. tropicalis will not.