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Biochemical testing for micro
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Questions in this quiz (49)
1Which of the two have the two enzymes that allow them to ferment lactose. Beta-galactoside permease - which serves as a transport enzyme that facilitates entry of lactose molecule across the bacterial plasma membrane and Beta-galactosidase - the enzyme that hydrolyzes lactose into its to components of glucose and galactose.
- ALactose fermenters (LFs)
- BNon Lactose fermenters (NLFs)
2Embden-Meyerhof pathway is also referred to as glycolysis.
- ATrue
- BFalse
3Bacteria that can grow either aerobically or anaerobically are called facultative anaerobes.
- ATrue
- BFalse
4Asaccharolytic are bacteria that do not use carbohydrates but instead use other organic molecules such as amino acids for energy and carbon sources.
- ATrue
- BFalse
5The Oxidation-Fermentation Test is helpful in differentiating members of the; (check all that apply)
- AFamily Enterobacteriaceae
- BGlucose fermenters
- CAerobic pseudomands and similar gram-negative bacteria which are nonfermenters
6The end product of carbohydrate fermentation is acid or acid with gas (O/F test)
- ATrue
- BFalse
7Some bacteria produce primarily a single acid, such as streptococci, which are homolactic acid fermenters, while other bacteria produce several different acids, including lactic acid, propionic acid, and succinic acid. These organisms are referred to as mixed acid fermenters.
- ATrue
- BFalse
8When acid is produced in both tubes, the isolate is an oxidizer and fermenter. The presence of acid in the open tube indicates only that the organism is a fermenter and possible obligate anaerobe, whereas the presence of acid in the open tube indicates an oxidizer. The open tube may or may not show acidity. No acid in production in the open tube may indicate that the organism is a non-oxidizer; many oxidizers produce an alkaline reaction from peptone utilization.
- ATrue
- BFalse
9One tube in a O/F test always contains mineral oil to create an anaerobic area
- ATrue
- BFalse
10Which indicator is used in the O/F testing
- ABromothymol Blue
- BPhenol Red
11For the O/F test uninoculated medium is (1); in an acid environment, the indicator is (2), and it is (3) in an alkaline environment
- A(1) - green, (2) - blue, (3) - yellow
- B(1) - green, (2) - yellow, (3) - blue
- C(1) - yellow, (2) - green, (3) - blue
- D(1) - blue, (2) - green, (3) - yellow
12For O/F testing, if both your tubes are yellow then it is (1), If your oil over-layed tube is green and your open tube is yellow then it is (2), if your oil over-layed tube is green and your open tube is green then it is (3)
- A(1) - oxidizer/nonfermenter, (2) - oxidizer/fermenter, (3) - nonoxidizer/nonfermenter
- B(1) - oxidizer/nonfermenter, (2) - nonoxidizer/nonfermenter, (3) - oxidizer/fermenter
- C(1) - oxidizer/fermenter, (2) - oxidizer/nonfermenter, (3) - nonoxidizer/nonfermenter
- D(1) - nonoxidizer/nonfermenter, (2) - oxidizer/fermenter, (3) - oxidizer/nonfermenter
13The "TSI" agar stands for Triple Sugar Iron and this agar is very similar in composition to KIA. Both of these are useful in the presumptive identification of gram-negative enteric bacteria, particularly in screening for intestinal pathogens
- ATrue
- BFalse
14TSI contains 1% sucrose in addition to 0.1% glucose and 1% lactose while KIA only contains 0.1% glucose and 1% lactose.
- ATrue
- BFalse
15Ferrous sulfate and sodium thiosulfate are not added to detect the production of hydrogen sulfide gas (H2S)
- ATrue
- BFalse
16Phenol red is used as the pH indicator, which is yellow below the pH of 6.8. Uninoculated medium is red because the pH is buffered at 7.4.
- ATrue
- BFalse
17Both TSI agar and KIA are useful in detecting the ability of the microorganism to ferment carbohydrates, glucose and lactose in KIA and glucose, lactose, or sucrose in TSI agar; to produce gas from the fermentation of sugars; and to detect the production of H2S.
- ATrue
- BFalse
18Both TSI agar and KIA are poured on a slant, the slant portion is aerobic and the butt or deep portion is anaerobic.
- ATrue
- BFalse
19To inoculate TSI agar or KIA, the laboratory scientist should pick a well-isolated colony with an inoculating needle and stab the butt almost all the wall to the bottom of the tube. The laboratory scientist then moves the needle back and forth known as fish tailing across the surface of of the slant. Cap is also replaced loosely to allow oxygen to enter the tube, and the medium is incubated in a non-CO2 incubator for 18-24 hours
- ATrue
- BFalse
20No fermentation on slant and butt, would be reported as (1). This would mean that they are unable to ferment either lactose or glucose or sucrose but these organisms can degrade the peptones present in the medium aerobically or anaerobically, resulting in the production of alkaline by-prodcuts in the slant or deep, respectively changing the indicator phenol red to a deep red colour. These reactions are typical of organisms that are not members of the family Enterobacteriaceae.
- A(1) - A/ALK
- B( 1) - A/A
- C(1) - ALK/A
- D(1) - ALK/ALK
21Glucose fermentation only, no lactose (or sucrose in TSI) would result in which reporting (1). If glucose is only utilized and knowing that their are peptones within the media what will happen to the Slant and Butt regions and how would they be reported. Explanation is listed if you look for it at the end of the quiz.
- A(1) - A/A
- B(1) - ALK/A
- C(1) - A/ALK
- D(1) - ALk/ALK
22If Lactose (or Sucrose or both) fermentation occurs how would you report this (1)? (Explanation is also found for this, can be checked at the end of the quiz)
- A(1) - ALK/ALK
- B(1) - ALK/A
- C(1) - A/A
- D(1) - A/ALK
23H2S production can occur with an alkaline slant/acid butt with H2S in butt reported as (1) or acid slant/ acid butt with H2S in butt reported as (2).
- A(1) - ALK/A H2S , (2) - A/A H2S
- B(1) - A/A H2S H2S , (2) - ALK/ALK H2S
24H2S production is a two-step process with the first step, H2S is formed from sodium thiosulfate. Because H2S is a colourless gas, the indicator, ferrous sulfate, is necessary to detect its production visually. In some cases, the butt of the tube is completely black, obscuring the yellow colour from carbohydrate fermentation. Because H2S production requires an aicd environment, even if the yellow colour cannot be seen, it is safe to assume glucose fermentation.
A. Bacterium (acid environment) + Sodium thiosulfate --> H2S gas
B. H2S + ferric ions --> ferrous sulfide (black precipitate)- ATrue
- BFalse
25ONPG stands for ortho-nitrophenyl-Beta-D-galactopyranoside and PNPG stands for p-nitrophenyl-Beta-D-galactopyranoside
- ATrue
- BFalse
26ONPG and PNGP test determine whether the organism is a dLF (One that lacks the enzyme (1) but posses (2)) or a true NLF.
- A(1) - beta galactoside permease, (2) - beta galactosidase
- B(1) - beta galactosidase, (2) - beta galactoside permease
27ONPG is structurally similar to lactose, but ONPG is more readily transported through the bacterial plasma membrane and does not require beta-galactoside permease. Beta- galactosidase hydrolyzes ONPG, a colourless compound, into galactose and o-nitrophenol a yellow compound. ONPG remains colourless if the organism is an NLF.
- ATrue
- BFalse
28The suspension is incubated at 35oC and positive results can generally be seen within 6 hours. Beta-galactosidase is an inducible enzyme, the gene is expressed only if lactose or a similar substrate is present; therefore bacteria should be taken from lactose-containing media for testing. Bacteria producing yellow pigment should not be tested because of a risk of a false-positive result
- ATrue
- BFalse
29Positive for an ONPG is (1) and a negative is (2)
- A(1) - red, (2) - blue
- B(1) - yellow, (2) - red
- C(1) - colourless, (2) - yellow
- D(1) - yellow, (2) - colourless
30The purpose of the Methyl Red test is in the identification and differentiation of the Enterobacteriaceae family by determining the organism's ability to produce and maintain stable acid by-products from glucose fermentation.
- ATrue
- BFalse
31When methyl red indicator is added to the broth, a red colour shows the presence of acid. The indicator turns yellow in a neutral pH. Initially all members of the Enterobacteriaceae family would yield a positive methyl red test. As incubation is extended to 2 days or longer, methyl red-positive organisms continue to produce acids, this acidic build-up is enough to counteract the phosphate buffering system leading to the true methyl red-positive endpoint. Methyl red-negative organisms readily decarboxylate the amino acid products formed during fermentation, which results in an increase in alkalinity and an alkaline pH shift - becoming yellow again
- ATrue
- BFalse
32Place the procedure in order from start to finish. For MR
- A1. Transfer inoculum from an 18-24 hour pure growth to below the surface of the medium. 2. Incubate the broth for 48 hours at 35oC aerobically. 3. Add 3 drops of methyl red indicator to the 0.5 mL aliquot; interpret the colour immediately
- B1. Incubate the broth for 48 hours at 35oC aerobically. 2. Transfer inoculum from an 18-24 hour pure growth to below the surface of the medium. 3. Add 3 drops of methyl red indicator to the 0.5 mL aliquot; interpret the colour immediately
- C1. Add 3 drops of methyl red indicator to the 0.5 mL aliquot; interpret the colour immediately. 2. Transfer inoculum from an 18-24 hour pure growth to below the surface of the medium. 3. Incubate the broth for 48 hours at 35oC aerobically.
33Positive MR is a distinct, stable, bright red colour at the surface of the broth while a Negative is a yellow colour at the surface of the broth
- ATrue
- BFalse
34If MR is positive, which organisms would this be indicative of? check all that apply
- AEscherichia coli
- BYersinia spp.
- CEnterobacter aergenes
- DEnterobacter cloacae
35If the MR is negative, which organisms would this be indicative of? check all that apply
- AEscherichia coli
- BYersinia spp.
- CEnterobacter aergenes
- DEnterobacter cloacae
- EOther gram-negative, non-enteric bacilli
36Voges Proskauer is a test used in the identification of the Enterobacteriaceae. It is primarily used to differentiate E. coli from the Klebsiella/Enterobacter group. It determines the organism's ability to produce acetoin from glucose fermentation.
- ATrue
- BFalse
37Some organisms break down glucose into 2,3 butanediol, which accumulates as acetoin (acetyle methyl carbinol) under aerobic conditions. when alpha-naphthol is added to a broth culture of the organism, the acetoin is converted to diacetyl, which combines with the alpha-naphthol and turns red. When potassium hydroxide (KOH) is added to acetoin in the presenceof oxygen, more acetoin is converted to diacetyl. The KOH must be added after the alpha-naphthol- if added before the alpha-naphthol, it may tuen the broth a faint pink. KOH aids in the absorption of CO2. If acetoin is present, a red colour develops over 10 mintues. The reaction is enhanced if the contents are mixed periodically to expose the contents of the tube to oxygen - this promotes the conversion of acetoin to diacetyl.
- ATrue
- BFalse
38For the procedure of VP testing what is the correct order of steps. (The inoculation procedure is the same as outlined for the MR test. Incubation is at 35oC for 18 to 24 hours in ambient air.)
- A1. Aseptically remove a 0.5 mL aliquot of broth and transfer to a test tube, label tube "VP". 2. Allow the tube to stand for 10-15 minutes before making an interpretation. 3. Gently shake the tube for 30 seconds to expose the suspension to oxygen. [This step oxidizes acetoin and emits a colour reaction. 4. First add 6 drops of 5% alpha-naphthol and gently shake; second, add 2 drops of 40% potassium hydroxide (KOH).
- B1. Aseptically remove a 0.5 mL aliquot of broth and transfer to a test tube, label tube "VP". 2. First add 6 drops of 5% alpha-naphthol and gently shake; second, add 2 drops of 40% potassium hydroxide (KOH). 3. Gently shake the tube for 30 seconds to expose the suspension to oxygen. [This step oxidizes acetoin and emits a colour reaction. 4. Allow the tube to stand for 10-15 minutes before making an interpretation.
39A positive VP is a pinkish red colour at the surface of the broth. reaction can be immediate for some organisms. A negative VP is a yellow to copper colour at the surface of the broth due to the reagents.
- ATrue
- BFalse
40For a positive VP which organisms would it be indicative of? check all that apply
- AKlebsiella pneumoniae
- BEnterobacter species
- CEscherichia coli
- DStaphylococcus species (usually +)
41A negative result for VP is indicative of which organisms. check all that apply.
- AStaphylococcus species (usually +)
- BEscherichia coli
- CMicrococcus species
- DKlebsiella pneumoniae
42Decarboxylase/Dihydrolase for Lysine, Ornithine and Arginine is to determine if an organism is able to decarboxylate or hydrolyze specified amino acids. This is useful in the differentiation of fermentative gram-negative bacilli, especially members of the family Enterobacteriaceae.
- ATrue
- BFalse
43Decarboxylation is a process in which the carboxyl group on an amino acid is removed leading to the formation of an amine or diamine plus CO2. Decarboxylation is an anaerobic reaction. Early in the decarboxylase or dihydrolase test, glucose is fermented creating an acid environment, which lowers the pH and causes production of a yellow colour. This acid condition can stimulate the production of decarboxylase or dihydrolase enzymes in certain organisms. Decarboxylase will work on lysine or ornithine producing diamines. The amines formed as the products of amino acid breakdown shift the pH to the alkaline range, causing the medium to change from yellow to purple.
- ATrue
- BFalse
44Steps for performing the procedure - 1. Inoculate a tube of decarboxylase media with the specific amino acid to be tested for each organism and a control tube (basal medium without amino acids); the inoculum must be light. 2. Overlay all tubes (including the control) with sterile mineral oil to a depth of at least 1.0 cm. 3. Incubate tubes at 35oC for 24 hours up to 4 days; examine daily
- ATrue
- BFalse
45For the control tube - Yellow colour indicating that the basal medium is functioning and the organism is viable. If purple, the test is invalid and the findings for all four should not be interpreted.
- ATrue
- BFalse
46Positive Test - Turbid grey/purple to faded out yellow-purple colour (purple) and a negative test is bright clear yellow indicating only glucose was fermented.
- ATrue
- BFalse
47Lysine indications for a positive test reaction are organisms Salmonella and E.coli and Negative test reaction are organisms Citrobacter spp and Shigella spp
- ATrue
- BFalse
48Ornithine indications for a positive test reaction are organisms Enterobacter (V, usually +) and Morganella morganii and Negative test reaction are organisms Klebsiella spp and Providencia spp
- ATrue
- BFalse
49Arginine indications for a positive test reaction are organisms Pseudomonas aeruginosa, Pseudomonas fluorescens, and Pseudomonas putida group and Negative test reaction are organisms Pseudomonas stutzeri
- ATrue
- BFalse
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- Quiz on Biochemical testing for micro, created by persha.hossaini on 03/02/2015.
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