Germ tube test

Germ tube test is done in mycology laboratories (  microbilogy laboratories that are studying fungi) to determine fungal infection in medical facilities. Germ tube test is a laboratory test which has a purpose to identify a kind of yeast Candida Albicans strains.

Candida Albicans creates a germ tube when they incubated ( waiting in a certain temperature and humidity in a certain time means incubation ) in a liquid media for 3 hours. Other yeast kinds can’t form a germ tube so germ tube test helps us to distinguish  candida albicans  from other yeast.

How the Germ Tube Test is Done ?

germ tube

1- Place 0.5 mL of human serum in a sterile tube

2- A little amount of  24 hour incubated yeast culture sample is inoculated ( adding or spreading culture sample into the culture media) in human serum

3-  Incubate the germ tube culture sample in laboratory oven  at 37° for  3  hours.

4- After 3 hours germ tube test sample will be ready for examination. Take a little drop on a microscope slide and analyse it under the microscope.

Germ Tube Test Results Evaluation

1-  Germ tube must be the half width  and 3-4 times length of yeast cell.

2-  There must not be any constriction at the point of yeast cell’s origin.

3- Germ tube’s edges must be paralel to each other.

4-  Germ tube must not be pieced.

After 3 hours of incubation if these signs are seen we can say that Germ Tube Test is positive (+) and the causative microorganism of  yeast infection is candida albicans. If results are found negative this doesn’t  exactly mean yeast is not candia albicans because % 5 of candia albicans can’t create a germ tube so some other laboratory tests must be done for exact diagnosis.


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