Chapter 09: Biochemical Identification of Gram-Negative Bacteria. All Answers

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MULTIPLE CHOICE 1. Biochemical tests are based on the _____ of microorganisms. a. phenotype b. genotype c. plasmid d. lysogeny A The colony morphology, Gram stain, and biochemical testi ... ng are based on the phenotype of the bacterium. The phenotype is the expressed characteristics in the bacteria. The genotype is the actual nucleic acid sequences present in the bacterium’s DNA. Plasmids can be responsible for antimicrobial resistance, but they do not alter colony morphology or biochemical tests. Lysogeny is infection of the bacteria with a virus. REF: 182 OBJ: Level 1: Recall 2. Nucleic acid assays are based on the _____ of the organism and are believed to be more accurate. a. phenotype b. genotype c. plasmid d. lysogeny B The genotype is the actual nucleic acid sequences present in the bacterium’s DNA. The colony morphology, Gram stain, and biochemical testing are based on the phenotype of the bacterium. The phenotype is the expressed characteristics in the bacterium. Plasmids can be responsible for antimicrobial resistance, but they do not alter colony morphology or biochemical tests. Lysogeny is infection of the bacteria with a virus. REF: 182 OBJ: Level 1: Recall 3. The initial screening of gram-negative rods is done by testing for the use of the carbohydrate: a. glucose. b. sucrose. c. lactose. d. mannitol. C Among bacteria, there is great diversity on the ability to utilize carbohydrates. However, the most important carbohydrate determination test is determining lactose utilization. Lactose degradation has been used to initially differentiate those bacterial species able to ferment lactose (LF) and those that are nonlactose fermenters (NLFs). REF: 182 OBJ: Level 1: Recall 4. Other sugars used to differentiate bacteria include all of the following except: a. raffinose. b. arabinose. c. rhamnose. d. sucralose. D Examples of sugars used to differentiate bacteria include lactose, maltose, rhamnose, sucrose, raffinose, arabinose, adonitol, dulcitol, mannitol, and sorbitol. REF: 183 OBJ: Level 1: Recall 5. Bacteria can use carbohydrates by: a. oxidation. b. synthesis. c. reduction. d. induction. A Oxidation is when the bacteria metabolize the carbohydrate aerobically, through the Embden-Meyerhof pathway. REF: 183 OBJ: Level 1: Recall 6. Some bacteria are asaccharolytic. This means that these bacteria: a. ferment glucose and use the Embden-Meyerhof pathway. b. do not utilize any carbohydrate; instead they use other organic molecules for energy. c. reduce glucose—that is, send it through the Entner-Doudoroff pathway. d. induce glucose into glycolysis, so that it can be oxidized. B Asaccharolytic bacteria do not use carbohydrates for energy. Instead these bacteria use proteins, sulfur, nitrogen, or other organic molecules for energy. By not using carbohydrates, they do not ferment, reduce, or induce glucose, and they do not use the Embden-Meyerhof and Entner-Doudoroff metabolic pathways. REF: 183 OBJ: Level 1: Recall 7. During this process, glucose enters the glycolysis pathway, resulting in the formation of pyruvic acid, which is further oxidized to other acids. What is this process called? a. Oxidation b. Reduction c. Fermentation d. Synthesis C This process is called fermentation. The end product of carbohydrate fermentation is acid or acid with gas. Oxidation also begins by glucose entering the glycolysis pathway; however, the pyruvic acid formed from glycolysis is further oxidized to CO2. Reduction and synthesis do not refer to processes related to carbohydrate utilization. REF: 183 OBJ: Level 2: Interpretation 8. Oxidative/fermentative (O/F) basal medium is a medium that will test the oxidative and fermentative capabilities of a microbe. The pH indicator is: a. sudan IV. b. phenolphthalein. c. bromcresol green. d. bromthymol blue. D Sudan IV is a fat stain. Phenolphthalein and Bromcresol green are other indicators with differing pH ranges than the bromthymol blue. REF: 183 OBJ: Level 1: Recall 9. When performing the oxidative/fermentative (O/F) test, one tube is covered with mineral oil and one tube is left uncovered. Why is one tube covered with mineral oil? a. To create an anaerobic (fermentative) environment b. To create an aerobic (oxidative) environment c. To create a reductive environment d. To create an asaccharolytic environment A When O/F tests are performed, two tubes of OFBM are inoculated; one is overlayed with sterile mineral oil to create an anaerobic environment (closed), and the other tube is left aerobic (open), without mineral oil overlay. This allows the bacteria the opportunity to oxidize or ferment the carbohydrates present in this media. The O/F tests do not create reductive or asaccharolytic environments. REF: 183 OBJ: Level 2: Interpretation 10. A technician is reading the biochemical tests for identifying a particular gram-negative rod. The organism has produced acid, indicated by a color change, in the closed tube only. This indicates that the organism is: a. an oxidizer. b. a fermenter. c. both an oxidizer and a fermenter. d. a reducer. B Bacteria that utilize carbohydrates in an anaerobic environment are called fermenters. Bacteria that utilize carbohydrates in an aerobic environment are called oxidizers; this would cause a color change in the open tube. If color changes occurred in both the anaerobic and aerobic tubes, the bacteria would be considered an oxidizer and a fermenter. Reducers will not cause color changes in this media. REF: 183 OBJ: Level 2: Interpretation 11. What are the sugars present in triple sugar iron (TSI)? a. Sucrose, glucose, lactose b. Mannitol, lactose, arabinose c. Sucrose, glucose, rhamnose d. Lactose, sucrose, raffinose A TSI contains sucrose in addition to glucose and lactose. REF: 183 OBJ: Level 1: Recall 12. What chemicals are added to triple sugar iron (TSI) to detect the production of hydrogen sulfide gas? a. Phenol red and ferrous sulfate b. Bromthymol blue and sodium thiosulfate c. Ferrous sulfate and sodium thiosulfate d. Copper sulfate and ferrous sulfate C Ferrous sulfate and sodium thiosulfate are added to TSI to detect the production of hydrogen sulfide gas. REF: 183 OBJ: Level 1: Recall 13. To inoculate triple sugar iron (TSI) agar or Kligler’s iron agar (KIA), the laboratory scientist should pick a well-isolated colony with an inoculating needle and: a. touch the bottom of the needle to the bottom of the slant portion of the agar and move the needle back and forth across the surface of the slant all the way to the top of the tube. b. touch the bottom of the needle to the top of the slant portion of the agar and move the needle back and forth across the surface of the slant all the way to the bottom of the tube. c. touch the bottom of the needle to the bottom of the slant portion of the agar and move the needle up the slant in a straight line all the way to the top of the tube. d. stab the butt almost all the way to the bottom of the tube, then move the needle back and forth over the surface of the slant all the way to the top of the tube. D You need to stab the butt of the tube to allow the bacteria to be in an anaerobic environment for fermentation to take place. The bacteria need to be spread over the slant portion of the TSI so that the bacteria can have an aerobic environment for oxidization. REF: 184 OBJ: Level 2: Interpretation 14. These bacteria are unable to ferment either lactose or glucose, but they can degrade the peptones present in the triple sugar iron (TSI) agar or Kligler’s iron agar (KIA) aerobically or anaerobically, resulting in the production of alkaline by-products in the slant or deep, respectively, changing the indicator to a deep red color. What kind of bacteria cannot ferment lactose or glucose? a. Nonenteric bacilli b. Anaerobic bacilli c. Gram-positive cocci d. Gram-positive rods A The nonenteric bacteria are unable to ferment either lactose or glucose, but they can degrade peptones in the slants, resulting in the production of alkaline by-products, changing the indicator to a deep red color. REF: 184 OBJ: Level 2: Interpretation 15. If an organism fermented glucose only and utilized peptones, what would the triple sugar iron (TSI) reaction be? a. Acid/acid b. Alkaline/acid c. Alkaline/alkaline d. Acid/alkaline B The acid produced from this concentration of glucose is enough to initially change the indicator to yellow throughout the medium. After 12 hours, the glucose will be consumed and the bacteria on the slant will utilize the peptones aerobically, producing an alkaline reaction, changing the indicator to a deep red color. REF: 184 OBJ: Level 2: Interpretation 16. If a bacterium utilizes lactose or sucrose, what will the triple sugar iron (TSI) reaction look like? a. Alkaline/acid b. Alkaline/alkaline c. Acid/acid d. Acid/alkaline C Glucose fermenters will attack the simple sugar glucose first and then the lactose or sucrose. The acid production from the fermentation of the additional sugar(s) is sufficient to keep both the slant and the butt acid (yellow) when examined at 18 to 24 hours. REF: 184 OBJ: Level 2: Interpretation 17. If a bacterium utilizes lactose or sucrose and produces H2S, what will the triple sugar iron (TSI) reaction look like? a. Acid/acid, black butt b. Acid/alkaline, black butt c. Alkaline/alkaline, black slant d. Alkaline/acid, black slant A Because the bacteria utilize lactose, sucrose, or both, the slant and the butt should be black. The visualization of H2S is a two-step process. In the first step, H2S is formed from sodium thiosulfate. Because H2S is a colorless gas, the second indicator, ferrous sulfate, is necessary to visually detect its production. In some cases, the butt of the tube will be completely black, obscuring the yellow color from carbohydrate fermentation. Because H2S production requires an acid environment, even if the yellow color cannot be seen, it is safe to assume glucose fermentation. REF: 184 OBJ: Level 2: Interpretation 18. Which test determines if an organism is a delayed lactose-fermenter? a. -Galactosidase b. Dihydroxylase c. Nitrate d. Ortho-nitrophenyl--D-galactopyranoside (ONPG) test D The ONPG test determines whether the organism is a delay lactose-fermenter (one that lacks the enzyme -galactoside permease but possesses -galactosidase) or a true nonlactose-fermenter. REF: 185 OBJ: Level 1: Recall 19. The chemical reaction for the Ortho-nitrophenyl--D-galactopyranoside (ONPG) test is: a. -galactosidase hydrolyzes lactose into glucose and galactose. b. glucose  pyruvic acid  acetoin. c. -galactosidase hydrolyzes o-nitrophenyl--D-galactopyranoside into galactose and o-nitrophenol (a yellow compound). d. O-nitrophenyl--D-galactopyranoside is oxidized into acetoin and glucose. C ONPG is structurally similar to lactose, but it is more easily transported through the bacterial cell wall and does not require -galactoside permease. -Galactosidase hydrolyzes ONPG, a colorless compound, into galactose and o-nitrophenol, a yellow compound. ONPG remains colorless if the organism is a nonlactose fermenter. REF: 185 OBJ: Level 1: Recall 20. The methyl red test detects metabolic by-products from what pathway? a. Mixed acid fermentation pathway b. Butylene glycol pathway c. Citrate pathway d. Clark and Lubs pathway A Glucose is metabolized via the Embden-Meyerhof pathway, producing several intermediate by-products, including pyruvic acid. Further degradation of pyruvic acid can produce mixed acids as final end products. However, enterics take two separate pathways: the mixed acid fermentation pathway or the butylene glycol pathway. The methyl red test detects the end products from the mixed acid pathway. REF: 185 OBJ: Level 1: Recall 21. The biochemical pathway that the methyl red test confirms is: a. glucose  pyruvic acid  mixed acid fermentation. b. pyruvic acid  glucose mixed acid fermentation. c. glucose pyruvic acid  acetoin diacetyl KOH. d. butylene  pyruvic acid  diacetyl KOH. A Bacteria are incubated in a media containing glucose. The bacteria utilize the glucose via the Embden-Meyerhof pathway. The end product of this pathway is pyruvic acid. Bacteria continue to oxidize the pyruvic acid into a variety of other acids. An indicator is added to the broth that will turn deep red if it is at a low pH. REF: 185 OBJ: Level 2: Interpretation 22. The two reagents used in the Voges-Proskauer test are: a. methyl red and acetoin. b. 40% KOH and methyl red. c. o-nitrophenol and -naphthol. d. 40% KOH and -naphthol. D After incubating the broth containing the bacteria and glucose, -naphthol is added as a catalyst or color intensifier. Next, 40% KOH is added, and the tube is gently shaken to increase oxygenation. Under these conditions, acetoin is oxidized to diacetyl, which forms a red complex. REF: 186 OBJ: Level 1: Recall 23. In the Voges-Proskauer test, you are testing for the metabolic by-products of which pathway? a. Glucose  formic acid formaldehyde b. Glucose pyruvic acid mixed acid fermentation c. Lactose  glucose 2,3 butanediol d. Glucose pyruvic acid acetoin diacetyl KOH D In some bacteria, acids formed during fermentation can be further metabolized to 2,3-butanediol through the intermediate acetoin. After incubating the broth containing the bacteria and glucose, -naphthol is added as a catalyst or color intensifier. Next, 40% KOH is added, and the tube is gently shaken to increase oxygenation. Under these conditions, acetoin is oxidized to diacetyl, which forms a red complex. REF: 186 OBJ: Level 2: Interpretation 24. The decarboxylase tests determine: a. whether the bacteria possess enzymes capable of removing the carboxyl group of specific amino acids in the test medium. b. whether the bacteria can further metabolize the acids formed during fermentation to 2,3 butanediol. c. if bacteria can maintain an acid pH if only sucrose is present in the media. d. to see if -naphthol can be broken down into its constituent parts: acetoin and diacetyl KOH. A Some bacteria use amino acids as energy and carbon sources. This test determines what specific amino acids the bacteria are capable of decarboxylating. REF: 187 OBJ: Level 2: Interpretation 25. Decarboxylase tests exist for all the following amino acids except: a. lysine. b. tyrosine. c. ornithine. d. arginine. B The products of decarboxylation are amine or diamine molecules and carbon dioxide, with resulting alkalinity. These are the only amino acids for which decarboxylase is measured. REF: 187 OBJ: Level 1: Recall 26. The medium used in the decarboxylase test is called _____ decarboxylase base medium. a. Clark’s b. Voges’ c. Moeller’s d. OF C Moeller’s decarboxylase base medium is a broth containing glucose, peptones, bromcresol purple, cresol red, and the specific amino acid to be tested. REF: 187 OBJ: Level 1: Recall 27. Why does the Moeller decarboxylase base medium contain glucose if it is testing the decarboxylation of amino acids? a. The decarboxylation of the amino acids takes place during the glucose metabolic pathway. Once glucose is broken down into pyruvic acid, then the amino acid is modified. b. To get the energy needed to take the carboxyl group off the amino acid, the bacteria must have glucose. c. When glucose is fermented, one of the by-products is acetoin. This acetoin is part of the mechanism that cleaves the carboxyl group from the specific amino acid. d. Decarboxylases are inducible enzymes produced in an acid pH. D For decarboxylation to take place, two conditions must be met: an acid PH and an anaerobic environment. A control tube containing the base medium without the amino acid is tested along with the test organism to determine the viability of the organism. The control tube also determines whether sufficient acid is produced. Decarboxylation does not take place during glucose metabolism because glucose metabolism is utilizing carbohydrates. Decarboxylation takes place when using proteins for energy instead of carbohydrates. The bacteria do need energy, but when they are unable to use glucose as an energy source, then proteins are used for energy. Acetoin does not cleave carboxyl groups from amino acids. Acetoin is an intermediate product in glucose fermentation. REF: 187 OBJ: Level 2: Interpretation 28. Using Moeller’s decarboxylase base medium, what color is a positive reaction and what causes this color to be produced? a. Purple; alkaline environment produced b. Yellow; acid environment produced c. Purple; acid environment produced d. Yellow; alkaline environment produced A Bromcresol purple, the indicator, turns purple when an alkaline environment is produced after the carboxyl group is cleaved. Yellow is produced in an acid environment, but the resulting environment in the tube is alkaline. REF: 187 OBJ: Level 2: Interpretation 29. Bacteria demonstrating weak decarboxylase activity: a. will have a false-negative test. b. may take up to 4 days to be positive. c. require extra reagents to show the positive reaction. d. will have a false-positive test. B Results can usually be recorded in 24 hours, but bacteria with weak decarboxylase activity may take up to 4 days to be positive. The enzymes are inducible in an acid environment, so until the acid environment is sufficient, the enzymes will not be produced and the reaction will not occur. REF: 187 OBJ: Level 2: Interpretation 30. Amino acids can be metabolized by these substances that remove an amine group. What is this substance? a. Amino acidase b. Amylase c. Deaminase d. Decarboxylase C Deaminases are enzymes that take an amine group off the amino acid—de, amin, ase: take away, amine, enzyme. Decarboxylase is an enzyme that removes a carboxyl group. Amylase is an enzyme that breaks down starch. REF: 187 OBJ: Level 1: Recall 31. What test is useful in the initial differentiation of Proteus, Morganella, and Providencia species from the rest of the Enterobacteriaceae? a. Oxidation-fermentation b. Methyl red c. Amino acid decarboxylase d. Phenylalanine deaminase D The phenylalanine deaminase test determines whether an organism possesses the enzyme that deaminates phenylalanine to phenylpyruvic acid. This helps differentiate Proteus, Morganella, and Providencia species from other Enterobacteriaceae. Oxidation-fermentation is used to determine the oxidative and fermentative capabilities of an organism. Methyl red determines if bacteria further metabolize pyruvic to mixed acids. REF: 187 OBJ: Level 2: Interpretation 32. What reagent is used to demonstrate a positive phenylalanine deaminase test? a. 10% Ferric chloride b. Methyl red c. -Naphthol d. 40% Sodium hydroxide A The addition of 10% ferric chloride results in a green color if phenylpyruvic acid is present. Methyl red is an indicator found in the methyl red test broth. Both -naphthol and 40% sodium hydroxide are used in the Voges-Proskauer test. REF: 187 OBJ: Level 1: Recall 33. The principle of the citrate test includes all the following except: a. bacteria able to use citrate will use the ammonium salts releasing ammonia. b. the alkaline pH that results from use of the ammonium salts changes the pH indicator. c. the pH indicator changes from red to bright yellow. d. the pH indicator changes from green to blue. C The indicator in Simmons citrate is bromthymol blue, which changes from green to blue in an alkaline pH. REF: 187 OBJ: Level 2: Interpretation 34. A bacterial DNase is a(n): a. oligonucleotide formed from a native DNA. b. oligonucleotide formed from a native RNA. c. proteolytic enzyme that forms extracellular DNA in the bacterial cell. d. endonuclease that cleaves internal phosphodiester bonds, resulting in smaller subunits of DNA. D A DNase is an enzyme (endonuclease) that cleaves DNA. A proteolytic enzyme is one that cleaves proteins. The oligonucleotides are formed by the action of the DNase. REF: 188 OBJ: Level 1: Recall 35. Extracellular DNase can be produced by: a. Staphylococcus aureus. b. Streptococcus agalactiae. c. Micrococcus luteus. d. Haemophilus influenzae. A S. aureus and S. marcescens are two different bacteria that can produce extracellular DNase. REF: 188 OBJ: Level 2: Interpretation 36. Some bacteria produce these enzymes that break down gelatin into amino acids. These enzymes are called: a. DNase. b. gelatinase. c. proteolytic. d. malonate. B The enzyme that breaks down gelatin into amino acids is called gelatinase. DNase breaks down DNA into smaller pieces called oligonucleotides. Proteolytic refers to a class of enzymes that break down proteins in general. REF: 188 OBJ: Level 1: Recall 37. What amino acid is the substrate in indole test broth? a. Ornithine b. Arginine c. Tryptophan d. Leucine C Indole is one of the degradation products of the amino acid tryptophan. Organisms that possess the enzyme tryptophanase are capable of deaminating tryptophan, with the formation of the intermediate degradation products of indole, pyruvic acid, and ammonia. REF: 188 OBJ: Level 1: Recall 38. What two reagents can be used to visualize indole in the broth? a. Indole and xylene b. 40% Sodium hydroxide and -naphthol c. 10% Ferric chloride d. Ehrlich’s and Kovac’s D Ehrlich’s and Kovac’s reagents both contain the indicator paradimethylaminobenzaldehyde that turns red in the presence of indole. Indole is the by-product that is of interest. Forty percent sodium hydroxide and -naphthol are used in the Voges-Proskauer test. Ten percent ferric chloride is used in the phenylalanine deaminase test. REF: 188 OBJ: Level 1: Recall 39. What type of medium is used in the motility test? a. Semisolid b. Cornmeal c. Sabouraud dextrose d. Peptone gel A Motility is determined by observing growth in a semisolid medium. The motility test media have agar concentrations of 0.4% or less, to allow for free spread of organisms. Cornmeal and Sabouraud dextrose are two media used for fungal cultures. REF: 189 OBJ: Level 1: Recall 40. A positive test for motility: a. turns the motility media blue. b. shows hazy appearance throughout or movement away from a stab. c. appears as a scum on the top of the media. d. will turn blue after the addition of the indicator bromthymol blue. B Motile organisms will move away from the stab line or will move throughout the media. Motility media do not have indicators added to them. The bacteria do not form a scum on the top of the media; they stay in the media and spread out there. REF: 189 OBJ: Level 2: Interpretation 41. What two reagents are needed to visualize nitrite in the nitrate reduction test? a. Sulfanilic acid and 40% sodium hydroxide b. Sulfuric acid and -naphthol c. N,N-dimethyl--naphthylamine and sulfanilic acid d. N,N-dimethyl--naphthylamine and sulfuric acid C The organism is inoculated into a nutrient broth containing a nitrogen source. After 24 hours of incubation, N,N-dimethyl--naphthylamine and sulfanilic acid are added. A red color indicates the presence of nitrite. REF: 189 OBJ: Level 1: Recall 42. What does the oxidase test determine? a. If the bacteria have the enzyme, oxidase, to reduce oxygen to carbon dioxide b. If the bacteria have oxidase, which will allow for the oxidation of carbohydrates c. If the bacteria can hydrolyze urea to ammonia and carbon dioxide d. The presence of the cytochrome oxidase system that oxidizes reduced cytochrome with molecular oxygen D The oxidase test is helpful in differentiating between the Enterobacteriaceae, oxidase negative, and the pseudomonads. When a 1% aqueous solution of tetramethyl-p-phenylenediamine dihydrochloride is added, the development of a lavender color is positive. REF: 189 OBJ: Level 2: Interpretation 43. What medium is used in the urease test? a. Christensen’s media b. Loeffler’s media c. Moeller’s oxidative broth d. Kovac’s reagent A Christensen’s urea agar is generally preferred. It contains urea and phenol red as the indicator. A positive test turns a bright pink test. Kovac’s reagent is used for the indole test. REF: 190 OBJ: Level 1: Recall 44. What does a lysine iron agar (LIA) slant contain? a. Ornithine, glucose, ferric ammonium chloride, and urea b. Lysine, glucose, ferric ammonium citrate, and sodium thiosulfate c. Acetoin, pyruvic acid, nitrate, and sulfanilic acid d. Arginine, lactose, ferric chloride, sodium hydroxide, and urea B The components of this slant include lysine, glucose, ferric ammonium citrate, and sodium thiosulfate. LIA is used primarily to determine whether the bacterial species decarboxylates or deaminates lysine. Hydrogen sulfide production is also detected in this medium. REF: 190 OBJ: Level 1: Recall 45. The lysine iron agar (LIA) slant is also useful in differentiating: a. Acinetobacter and Alcaligenes. b. Klebsiella and Enterobacteriaceae. c. Proteus, Morganella, and Providencia. d. Escherichia, Salmonella, and Campylobacter. C This group of enterics deaminates (attacks the NH2 group instead of the carboxyl group) amino acids. In the LIA slant, deamination of lysine turns the original light purple color slant to a plum or reddish purple color; the butt turns yellow because of glucose fermentation. REF: 190 OBJ: Level 2: Interpretation 46. Commercial identification systems fall into all of the following categories except: a. pH-based reactions. b. enzyme-based reactions. c. visual detection of bacterial growth. d. use of nitrogen and sulfur sources. D Commercial identification systems fall into one of five categories or a combination thereof: pH-based reactions, enzyme-based reactions, utilization of carbon sources, visual detection of bacterial growth, or detection of volatile or nonvolatile fatty acids by gas chromatography. REF: 190 OBJ: Level 1: Recall 47. How are organisms identified with commercial identification kits? a. Numeric codes b. Color codes c. Alphabetic codes d. Alphanumeric codes A These numeric codes are generated based on the metabolic profiles of each organism. Each metabolic reaction, or phenotype, is translated into one of two responses: + or –. These plus/minus sequences are cataloged as binary numbers and stored in a computer database. REF: 190 OBJ: Level 1: Recall 48. This identification system for Enterobacteriaceae has a series of 20 cupules attached to a plastic strip. Inside the cupules are lyophilized pH-based substrates. What is the name of this system? a. ID Tri-Panel b. API 20E c. Microbact d. Enterotube II B The Analytical Profile Index (API 20E) has a series of 20 cupules attached to a plastic strip with lyophilized pH-based substrates inside the cupules. The principles of the tests are similar to those performed in the test tubes. REF: 191 OBJ: Level 1: Recall 49. Rapid identification of clinical isolates often involves commercially packaged identification kits and fully automated instruments. What do these kits use to assess the preformed bacterial enzymes? a. Extraction kits b. Volatile benzenes c. Chromogenic or fluorogenic substrates d. Chemiluminescent substrates C The chromogenic substrates are colorless; when cleaved by a microbial enzyme, a colored compound is produced. Fluorogenic substrates are nonfluorescent until cleaved by microbial enzymes. Reaction endpoints may be reached after 2 to 6 hours of incubation. REF: 192 OBJ: Level 1: Recall 50. What advantage do the methods based on enzyme substrates have over conventional methods? a. They use filter paper as the structure to hold the bacteria. b. They reduce the amount of substrate needed for the reactions. c. They use fluorogenic substrates. d. They do not require growth of the organism in the system. D Because enzymatic methods involve preformed enzymes, they do not require multiplication of the organism (growth independent). Therefore, endpoints are reached in minutes to a few hours. REF: 192 OBJ: Level 1: Recall 51. The Vitek AutoMicrobic System is manufactured by: a. Abbott. b. bioMérieux. c. Dade Behring. d. Becton Dickinson. B bioMérieux makes the Vitek AutoMicrobic System. REF: 195 OBJ: Level 1: Recall 52. Which system provides rapid identification of gram-negative bacteria through the use of cards? a. MicroScan b. BD Phoenix 100 c. Vitek AutoMicrobic system d. Sherlock Microbial Identification system C MicroScan and BD Phoenix use microtiter panels. The Sherlock Microbial Identification system uses a gas chromatograph to identify bacteria. REF: 195 OBJ: Level 1: Recall [Show More]

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