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Oxidase Test
- The oxidase test identifies organisms that produce the enzyme cytochrome oxidase.
- If the test organism produces cytochrome oxidase, the oxidase reagent will turn blue or purple within 15 seconds.
- E.coli : -
- Pseudomonas : +
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Catalase Test
- Identify organism that produce Catalase.
- Enzyme that breaks hydrogen peroxide H2O2 -> H2O & O2 (Bubble : +)
- Staphylococcus aureus : +
- Enterococcus : -
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Nitrate Reduction Test
- used to determine the ability of an organism to reduce nitrate -> nitrite using enzyme nitrate reductase.
- NO3 -NitrateReductase-> NO2
- E.Coli : +
- Bacillus : +
- Pseudomonas : +
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Phenol Red Broth
- used to differentiate gram negative enteric bacteria.
- Phenol red is a pH indicator which turns
- yellow < pH 6.8 and fuchsia > pH 7.4
- E.Coli : +
- Proteus : -
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Methyl Red (MR) and Veges-Proskauer (VP)
- If the organism uses the mixed acid fermentation pathway and produces stable acidic end-products.
- The MR and VP tests are particularly useful in the identification of the Enterobacteriaceae.
- E.coli : + Red
- Enterobacter : - No change(yellow)
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Starch Hydrolysis
- To identify the organism to produce amylase that hydrolyze starch.
- Bacillus : +
-
Citrate Test
- To tests the ability of organisms to utilize citrate as a carbon source (Green : -, Blue : +)
- E.Coli : -
- Enterobacter : +
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Sulfur Reduction
- If an organism can reduce sulfur to hydrogen sulfide, the hydrogen sulfide will combine with the iron to form ferric sulfide, which is a black precipitate. If there is any blackening of the medium, it indicates the reduction of sulfur and is a positive result.
- Black : +
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Indole
- Ability of organism to produce Indole using enzyme tryptophanase.
- The Kovac’s reagent is added to the SIM medium to test for indole
- Pink Ring : + (E.coli)
- Clear Ring : -
- Enterobacter : -
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Motility Test
- The preferred way to determine motility is to use the semi-solid medium
- If the growth around the stab line has radiated outwards in all directions or if the entire tube has turned pink, your organism is motile.
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Gelatinase Test
- To tests the ability of an organism to produce an enzyme called gelatinase, that hydrolyzes gelatin.
- Liquid : +
- Staphyloccus Aureus : +
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Urease Test
- To test the ability of an organism to produce an enzyme, called urease that hydrolyzes urea to ammonia & carbon dioxide.
- Pink : + (Proteus)
- Yellow : - (E.coli)
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