Podcast
Questions and Answers
What is the purpose of the citrate test?
What is the purpose of the citrate test?
- To distinguish bacteria capable of growth in a citrate medium (correct)
- To determine the ability of an organism to hydrolyze DNA
- To differentiate organisms based on the production of deoxyribonuclease
- To determine the growth of bacteria in a medium
What happens to the pH of the medium when bacteria grow in it?
What happens to the pH of the medium when bacteria grow in it?
- It becomes alkaline (correct)
- It changes randomly
- It becomes acidic
- It remains neutral
What is the function of the bromthymol blue indicator?
What is the function of the bromthymol blue indicator?
- To determine the pH of the medium (correct)
- To differentiate organisms based on the production of deoxyribonuclease
- To determine the growth of bacteria in a medium
- To determine the ability of an organism to hydrolyze DNA
What is the purpose of the DNA hydrolysis test?
What is the purpose of the DNA hydrolysis test?
What is the color of the DNA-methyl green complex?
What is the color of the DNA-methyl green complex?
What happens to the color of the medium if an organism can hydrolyze DNA?
What happens to the color of the medium if an organism can hydrolyze DNA?
What is the primary purpose of the test described?
What is the primary purpose of the test described?
What is the role of the MR indicator in the test?
What is the role of the MR indicator in the test?
What is the color of the MR indicator at pH 4.4?
What is the color of the MR indicator at pH 4.4?
What does a clear red result indicate?
What does a clear red result indicate?
What does the VP test detect?
What does the VP test detect?
What is the purpose of the VP test?
What is the purpose of the VP test?
What type of fermentation is detected by the MR indicator?
What type of fermentation is detected by the MR indicator?
What is the result of a yellow MR indicator?
What is the result of a yellow MR indicator?
What is a characteristic of E. coli O157:H7?
What is a characteristic of E. coli O157:H7?
What is the primary reservoir of Edwardsiella tarda?
What is the primary reservoir of Edwardsiella tarda?
What is a common source of Salmonella transmission?
What is a common source of Salmonella transmission?
What is a characteristic of Shigella?
What is a characteristic of Shigella?
What is a common location for Shigella infection?
What is a common location for Shigella infection?
What is a characteristic of Citrobacter freundii?
What is a characteristic of Citrobacter freundii?
What is a characteristic of Salmonella typhi?
What is a characteristic of Salmonella typhi?
What is a way to differentiate Edwardsiella tarda from Salmonella?
What is a way to differentiate Edwardsiella tarda from Salmonella?
What is the characteristic of Salmonella in the citrate test?
What is the characteristic of Salmonella in the citrate test?
Which of the following bacteria is a Rapid Lactose Fermenter?
Which of the following bacteria is a Rapid Lactose Fermenter?
What is the characteristic of Enterobacter in the citrate test?
What is the characteristic of Enterobacter in the citrate test?
Which of the following bacteria is a Late Lactose Fermenter?
Which of the following bacteria is a Late Lactose Fermenter?
What is the characteristic of Serratia in the citrate test?
What is the characteristic of Serratia in the citrate test?
Which of the following bacteria is a Non-Lactose Fermenter?
Which of the following bacteria is a Non-Lactose Fermenter?
What is the characteristic of Proteus in the citrate test?
What is the characteristic of Proteus in the citrate test?
Which of the following bacteria is aerogenic?
Which of the following bacteria is aerogenic?
What is the primary function of the test that determines an organism's ability to hydrolyze tryptophan?
What is the primary function of the test that determines an organism's ability to hydrolyze tryptophan?
What is the reaction between Kovac's reagent and indole?
What is the reaction between Kovac's reagent and indole?
What is the expected result of a positive test?
What is the expected result of a positive test?
What is the purpose of the Lysine Iron Agar (LIA) test?
What is the purpose of the Lysine Iron Agar (LIA) test?
What is the role of ferric ammonium citrate in Lysine Iron Agar?
What is the role of ferric ammonium citrate in Lysine Iron Agar?
What happens to the butt of the Lysine Iron Agar medium when glucose is fermented?
What happens to the butt of the Lysine Iron Agar medium when glucose is fermented?
What is the function of sodium thiosulfate in Lysine Iron Agar?
What is the function of sodium thiosulfate in Lysine Iron Agar?
What is the composition of the medium in Lysine Iron Agar?
What is the composition of the medium in Lysine Iron Agar?
Study Notes
Microbiology Laboratory Tests
- Pyruvate can enter the organism's metabolic cycle for energy production
- Bacteria capable of growth in citrate medium convert ammonium phosphate to ammonia and ammonium hydroxide, creating an alkaline pH
- Bromthymol blue indicator turns from green to blue in the presence of alkaline pH
DNA Hydrolysis (Dnase Test Agar)
- Purpose: differentiate organisms based on deoxyribonuclease production
- Principle: determines an organism's ability to hydrolyze DNA
- Expected result: pink to wine-colored ring after adding Kovac's reagent
Tryptophanase Test
- Purpose: determines an organism's ability to hydrolyze tryptophan to form indole
- Principle: tryptophanase-producing bacteria hydrolyze tryptophan to pyruvate, ammonia, and indole
- Expected result: pink to wine-colored ring after adding Kovac's reagent
Lysine Iron Agar (LIA)
- Purpose: differentiates gram-negative bacilli based on decarboxylation or deamination of lysine and H2S formation
- Principle: lysine iron agar contains lysine, peptones, glucose, ferric ammonium citrate, and sodium thiosulfate
- Expected result: acid production (yellow) in the butt of the medium
Methyl Red (MR) and Voges-Proskauer (VP) Tests
- Purpose: determines the ability to produce and maintain stable acid end products from glucose fermentation
- Principle: methyl red detects mixed acid fermentation, and VP detects the ability to convert acid products to acetoin and 2,3-butanediol
- Expected result: clear red (positive), yellow (negative), or shades of orange (inconclusive)
Bacterial Identification
- Shigella: causes dysentery, found in crowded or substandard conditions
- Edwardsiella tarda: opportunistic, found in reptiles and fresh water fish
- Salmonella: causes typhoid fever, bacteremia, and enterocolitis, found in poultry
- Citrobacter freundii: causes nosocomial infections
- Klebsiella: causes pneumonia, found in humans and the environment
- Enterobacter: causes opportunistic infections
- Serratia: causes opportunistic infections
- Proteus: causes urinary tract infections
- Morganella: causes opportunistic infections
- Providencia: causes opportunistic infections
- Yersinia: causes plague and gastrointestinal infections
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Description
A quiz on microbiology tests, including citrate test and DNA hydrolysis, to identify bacterial growth and hydrolysis of DNA.
