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118 Cards in this Set
- Front
- Back
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What differences are biochemical tests based on?
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metabolic, bacterial differences in enzymes
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What are the metabolic differences?
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oxygen requirement, glucose fermentation, ethanol production, acid toleration
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What is an important intermediate in glucose fermentation?
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pyurvate
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What may be pyruvate be fermented to?
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acetoin
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What test can glucose fermentation may be directly related to?
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VP Test
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What can ethanol that is produced as a byproduct of fermentation be used for?
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commercial use
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When can species produce and tolerate acid?
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after fermenting glucose
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How can production of acid be determined?
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low pH in a methyl red test
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What tests are done to test for metabolic intermediates of end products?
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methyl red, VP
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What tests are done for the presence of specific enzymes?
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catalase, oxidase, indole, urea hydrolysis, cysteine desulfurase
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What can cysteine desulfurase be detected as?
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hydrogen sulfide
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What is cysteine desulfurase released from?
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amino acid metabolism
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What are tests done in micro labs used to identify any new bacterial species from?
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patient, water, other environment
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What are the nutrient requirement tests?
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sugar fermentation, citrate test
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What is the medium for the sugar fermentation test?
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glucose, sucrose, lactose, or mannitol broth
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What are the reagents of the sugar fermentation test?
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bromothymol blue that is already in the media
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What are the interpetations of the sugar fermentation test?
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Positive: yellow, Negative: green
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What is the medium for the citrate test?
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Simmons citrate agar
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What are the reagents for the citrate test?
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Bromothymol blue (already in the media)
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What are the interpretations of the citrate test?
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Positive: blue, Negative: green
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What is the medium of the Methyl Red test?
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MR-VP broth
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What are the reagents of the methyl red test?
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3 drops of Methyl red
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What are the interpretations of the methyl red test?
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Positive: red, Negative: beige-yellow
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What is the medium for the VP test?
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MR-VP broth
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What are the reagents of the VP test?
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15 drop Barritt's A and B
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What are the interpretations of the VP test?
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Positive: pink within 20 minutes
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What is the medium of the catalase test?
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TSA
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What are the reagents of the catalase test?
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3 % H202
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What are the interpretations of the catalase test?
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positive: effervescence
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What is the medium for the oxdiase test?
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TSA
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What are the reagents of the oxidase test?
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Oxidase reagent
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What are the interpretations of the oxidase test?
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Positive: blue-black
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What is the medium of the indole test?
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tryptone broth
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What are the reagents of the indole test?
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Kovac's reagent, 5 drops
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What are the interpretations of the indole test?
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positive: red layer at top, negative: beige-yellow
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What is the medium for Urea hydrolysis?
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urea broth
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What are the reagents for urea hydrolysis?
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phenol red indicator already included
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What are the interpretations of the urea hydrolysis test?
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positive: bright-pink, negative: red-orange
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What is the medium of the H2S production test?
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Kligler's Iron Agar
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What are the reagents of the H2S production test?
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Ferrous sulfate included
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What are the interpretations of the H2S production?
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positive: black precipitate
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What does the indole test test for?
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production of indole from tryptophan (an amino acid)
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What does tryptophanase break down tryptophan into?
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indole, pyruvic acid, and ammonia
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What does the presence of indole implicate the presence of?
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tryptophanse
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What is the presence of indole in tryptophan visualized by?
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adding Kovac's reagent
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What forms when Kovac's reagent reacts with indole to give?
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a red complex
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What are the bacteria that were used in the indole test?
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E coli and E aerogenes or E. cloacae
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What does the methyl-red test test for?
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strong acid production from fermentation
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When does the methyl red turn red in the methyl red test?
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when the pH is at or below 4.4
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What produces acids during prolonged incubation and are called methyl red positive organism?
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Enterobacteriaceae
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What does enterobacteriaceae produce large amounts of?
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lactic, succinic, and acetic acid
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What kind of pH does enterobacteriaceae produce?
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very low
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How much ethanol do enterobacteriaceae produce?
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a small amount
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What does the small amount of ethanol that enterobacteriaceae produce result in?
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a large acid: alcohol ratio
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What kind of pH does a large acid:alcohol ratio result in?
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a very low one
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What happens if the organisms have formic hydrogenase?
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then equal amounts of CO2 and H2 are produced
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Why is gas not always produced
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some organisms do not contain the formic hydrogenase enzyme
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What is the MR test used to distinguish?
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enteric (intestinal) E. Coli, or soil organism (E. aerogenes)
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Why can some enteric or soil organisms be distinguished by the methyl-red test?
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they produce large amounts of acid when they ferment glucose
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What are the bacteria that were used in the MR test?
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E coli, E. aeroges, or E. cloacae
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When does the MR test turn red?
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for a pH less that 5
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What happens when the organism ferment glucose and produces acid in the MR test?
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the pH is lowered
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What does the VP test test for?
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the presence of acetoin
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What is acetoin the precursor of?
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2,3 butanediol
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What is one of the pathways of glucose degradation called?
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nuetral fermentation
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What is nuetral fermentation done via?
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pyruvic acid
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What does nuetral fermentation involve the production of?
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acetoin
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What do some organisms produce instead of mixed acids during fermentation?
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2,3- butanediol and EtOH
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What happens when some organisms produce 2,3-butanediol and EtOH instead of mixed acids during fermentation? (3 things)
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pH is not lowered as much, it is out of range of the methyl red test, and the methyl red test cannot be used
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Since the methyl red test is out of range for detecting 2,3 butanediol and EtOH, how is the presence of acetoin detected?
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VP test
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What does a positive VP test mean?
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a negative methyl red test
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Whart are the Bacteria used in the VP test?
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E.coli (plate), E. aerogenes, and E cloaecae
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What tests test for nutrient requirements?
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Sugar fermentation, citrate test
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What tests test for metabolic intermediates of end products?
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Methyl Red, VP
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What tests test for the presence of specific enzymes?
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catalase, oxidase, indole, urea hydrolysis, H2S production
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In the VP test, how are alcohols produced in terms of acid?
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larger amounts than acids
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What kind of acid:alcohol ratio is produced in the VP test?
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small
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What kind of pH is in the VP test?
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high
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What is produced in the VP test?
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a large amount of gas
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What is the proportion of CO2 compared to H2?
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greater
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How is the oxidase test done?
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quadrant streak
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What is the oxidase test used to detect the presence of?
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cytochrome c of the respiratory chain
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What are cytochromes?
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hemoproteins that transfer electrons to electron acceptors such as O2 in the electron transport system of the respiration pathway
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What is the dye that the oxidase test utilizes as an artificial electron donor?
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p-phenylenediamine dihydrochloride
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What happens to the dye in the presence of cytochrome C oxidase?
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it is oxidized
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What forms when the dye is oxidized?
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indophenol blue
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What bacteria are utilized in the catalase test?
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S. aureus, S. lactis
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What do most aerobes and facultatives that utilized oxygen generate?
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a superoxide radical that combines with a hydrogen ion to form hydrogen peroxie, catalyzed by superoxide dismutase
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What kind of metabolite is hydrogen peroxide?
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a toxic one
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How is the survival in the presence of hydrogen peroxide possible?
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because they produce an enzyme called catalase
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What does catalase convert hydrogen peroxide into?
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2H20 + O2
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What is the death of strict anaerobes in the presence of oxygen due to?
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the suicidal act of hydrogen peroxide production in the absence of catalase production
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What are the bacteria that were used in the catalase test?
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s. aureus, s. lactis
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What does hydrolysis of urea by urease lead to production of?
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ammonia
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What does ammonia form into in Stuart Medium?
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ammonium carbonate
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WHat does the production of ammonium carbonate result in?
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a pH increase
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What bacteria are used in the Urease test?
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E. coli, P. vulgaris
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What does the cysteine desulfurase test detect?
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hydrogen sulfide
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What is used to detect H2S in the cysteine desulfurase test?
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Kligler's Iron Agar
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What does the medium in the cysteine desulfurase test contain?
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ferrous sulfate
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What does ferrous sulfate from when it reacts with H2S?
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a dark precipitate of iron sulfide
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What does the cysteine desulfurase test also contain?
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glucose, lactose, and phenol red
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When KIA is used in slants, what is it also excellent for detecting?
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glucose and lactose fermentation
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What does a yellow color in the cysteine desulfurase test mean?
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a positive fermentation
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WHat is the sole source of carbon in the citrate test?
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sodium citrate
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What is the source of nitrogen in the citrate test?
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ammonium salts
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What does organism growth mean in the citrate test?
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alkalinity and an increased pH
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What does the citrate test detect?
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if a microogranism uses citrate as the sole source of carbon
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What is sugar fermentation done in?
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Durham tubes
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What does fermentation prove in the sugar fermentation test?
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acid production
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What happens to pH when acid is produced in the sugar fermentation test?
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it is lowered
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What does urease test determine?
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the ability of an organism to hydrolyze urea
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What does urease convert into?
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ammonia
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What happens to pH when urease converts into ammonia?
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pH increases
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What is the urea reaction?
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2 NH2s convert into C double bod o, and in the presents of urease and water convert into 2 NH4+ and CO2
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What does Kligler's Iron Agar contain?
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ferrous sulfate
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ferrous sulfate + H2S =
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iron sulfide (dark precipitate)
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What does KIA also contain?
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sugars and phenol red (which can indicate sugar fermentation)
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