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Questions and Answers
Ferric __________ production results in a black color on TSI agar.
Sulfide
On Citrate agar, a positive result shows __________ growth with or without a color change.
growth
In the Voges-Proskauer test, a positive result appears as a __________ color.
red
In the Sulfide Indole Motility test, motility is indicated by __________ in the agar.
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The Urease test uses __________'s Urea Agar.
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In the Antibiotic Susceptibility Testing, a positive result is indicated by a __________ of inhibition.
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In the Methyl Red test, a positive result appears as a __________ color.
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On LIA agar, a negative result appears as __________/yellow, indicating Lysine Deamination.
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Enterobacteriaceae are gram ______ bacteria.
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The oxidase test determines the presence of the ______ oxidase system.
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The nitrate reduction test determines whether an organism has the ability to reduce ______ to nitrite.
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Gelatinase activity is detected by the loss of ______ of gelatin.
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In the malonate utilization test, a positive result is indicated by a change in pH, turning the indicator from ______ to blue.
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In the oxidase test, a positive result is indicated by the development of a ______ color.
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MacConkey Agar and Eosin Methylene Blue are types of ______.
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The gelatin liquefaction test is used to detect the presence of ______ enzymes.
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B-galactoside permease and B-galactosidase are possessed by ______ LFs
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The O/F tests are performed using two tubes of ______ OFBM
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The pH indicator used in the O/F tests is ______ blue
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The TSI agar is used to determine the utilization of ______ and lactose or sucrose
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The composition of TSI agar includes 10 parts ______ and 10 parts sucrose
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The reaction on TSI agar should be read within an ______ to 24-hour incubation period
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The presence of H2S production is indicated by a ______ precipitate
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The H2S production requires an ______ environment
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Study Notes
Enzymes and Lactose Fermentation
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In lactose fermentation, the enzyme β-galactosidase breaks down lactose into glucose and galactose, while β-galactoside permease facilitates the transport of lactose into the cell.
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Lactose-fermenting (LF) organisms possess both β-galactosidase and β-galactoside permease, enabling them to efficiently metabolize lactose.
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In contrast, non-lactose-fermenting (NLF) organisms lack both enzymes, making them unable to break down lactose.
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Late-lactose-fermenting (LLF) organisms, however, possess β-galactosidase but lack β-galactoside permease, resulting in delayed lactose fermentation.
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B-galactoside hydrolyzes lactose into glucose and galactose.
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LFs (lactose-fermenting) possess both B-galactoside permease and B-galactosidase.
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NLFs (non-lactose-fermenting) do not possess either enzyme.
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LLFs (late-lactose-fermenting) lack B-galactoside permease but possess B-galactosidase.
Oxidation-Fermentation Tests
- Uses Hugh-Leifson OFBM with Bromthymol blue as pH indicator.
- Two tubes are inoculated: one is overlaid with sterile mineral oil to create an anaerobic environment, and the other tube is left aerobic.
- Oxidation occurs aerobically; fermentation occurs anaerobically.
Triple Sugar Iron (TSI) Agar
- Composition: 10 parts lactose, 10 parts sucrose, 1 part glucose, and peptone.
- pH indicator: phenol red.
- H2S indicator: Ferrous sulfate and sodium thiosulfate.
- Reactions are read within 18-24 hours; otherwise, erroneous results are possible.
Other Biochemical Tests
- Methyl Red/Voges-Proskauer Test: determines acetoin production.
- Citrate Utilization on Simmons Citrate Agar: determines citrate utilization.
- Sulfide Indole Motility (SIM) Test: detects sulfide production, indole production, and motility.
- Lysine Iron Agar (LIA) Test: detects glucose and lysine deamination.
- Urease Test: detects urea hydrolysis.
- Antibiotic Susceptibility Testing: determines susceptibility to antibiotics.
Gelatin Liquefaction
- Detects gelatinase activity, which breaks down gelatin into amino acids.
Malonate Utilization
- Detects the ability to use malonate as a sole carbon source and ammonium sulfate as a nitrogen source.
Nitrate and Nitrite Reduction
- Determines the ability to reduce nitrate to nitrite and nitrite to nitrogen gas.
Oxidase Test
- Determines the presence of the cytochrome oxidase system that oxidizes reduced cytochrome with molecular oxygen.
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Description
This quiz covers the procedure and results of carbohydrate utilization on Triple Sugar Iron Agar (TSI), including methyl red and Voges-Proskauer tests. It involves inoculating colonies, incubating, and observing color changes and gas formation.
