Oxidation-Fermentation Test (OF Test 1)
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The purpose of this test is to determine whether an organism attacks sugars (in this case glucose is used) by fermentation or oxidation. Two tubes of Hugh & Leifon's medium are used. In one tube the medium is covered with vaseline. If the organism is an oxidizer it will produce acid only in the open tube (without vaseline), if it is a fermenter it will produce acid in the vaseline-covered tube and in the open tube. Some aerobic bacteria may use the peptone in the medium, producing ammonia, with resulting alkalinity (blue) in the top part of the open tube. The indicator used is bromthymol blue.
1. Uninoculated medium.
2 + 3. Fermentative reaction with gas-production in the closed tube: Escherichia coli.
4 + 5. Fermentative reaction with gas-production in the closed tube: Klebsiella.
Sometimes the Hugh and Leifson's medium can be used to determine whether an organism is motile. Motile bacteria will show diffuse growth away from the stab line. Non-motile bacteria will only show growth confined to the stab line. In the examples given here E. coli is motile and Klebsiella is non-motile.
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© Department of Veterinary Disease Biology 2011
Faculty of Health and Medical Sciences - University of Copenhagen
Denmark |
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