Lancefield Grouping & Hemolysis Testing Quiz
24 Questions
2 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the purpose of the methyl red test in microbiology?

  • To detect bacteria producing stable acidic end products from glucose (correct)
  • To identify bacteria that can utilize citrate as a carbon source
  • To differentiate between bacteria based on their ability to hydrolyze tryptophan
  • To identify bacteria based on their fermentation of lactose

Which differential medium is used in the Voges-Proskauer test?

  • Simmon’s citrate agar
  • MAcConkey agar
  • Tryptone broth
  • MR-VP broth (correct)

What pH indicator is used in the citrate hydrolysis test, and what does it change to indicate a positive result?

  • Bromthymol blue, turns blue (correct)
  • Methyl red, turns yellow
  • Phenol red, turns pink
  • Litmus, turns purple

Which product is detected in the indole test after adding Kovac’s reagent?

<p>Indole (C)</p> Signup and view all the answers

Which of the following fermentation pathways does the methyl red test assess?

<p>Mixed acid fermentation pathway (B)</p> Signup and view all the answers

In the citrate hydrolysis test, what do the alkaline products produced signify?

<p>The bacteria successfully utilized citrate as a carbon source (B)</p> Signup and view all the answers

What may cause a false negative result in carbohydrate fermentation tests?

<p>Testing a sample that has been stored for over 24 hours (D)</p> Signup and view all the answers

What is the primary substrate for the Voges-Proskauer test?

<p>Glucose (B)</p> Signup and view all the answers

What is the differential medium that distinguishes Proteus species based on urease production?

<p>Urea broth (D)</p> Signup and view all the answers

What is a common detectable product in the methyl red test?

<p>Acetic acid (B)</p> Signup and view all the answers

Which substrate is tested in urea broth to determine urease activity?

<p>Urea (C)</p> Signup and view all the answers

What color indicates a positive result for urease activity in urea broth?

<p>Bright pink (D)</p> Signup and view all the answers

What is the role of ammonia produced during the urea hydrolysis process?

<p>To increase the pH, making it more alkaline (A)</p> Signup and view all the answers

Which of the following mistakes could lead to a false result in a urease test?

<p>Contamination of the test sample (A)</p> Signup and view all the answers

What is the primary role of lactose in MacConkey agar?

<p>To differentiate bacteria based on their ability to ferment lactose (D)</p> Signup and view all the answers

What color indicates lactose fermentation in MacConkey agar?

<p>Pink/red colonies (A)</p> Signup and view all the answers

Which test series is used to differentiate members of the Family Enterobacteriaceae?

<p>IMViC series of tests (B)</p> Signup and view all the answers

Which of the following describes a potential mistake that could lead to false results on MacConkey agar?

<p>Incubating the agar for over 24 hours (D)</p> Signup and view all the answers

What is the pH indicator used in urea broth to demonstrate urease activity?

<p>Phenol red (D)</p> Signup and view all the answers

What is the purpose of triple sugar iron agar?

<p>To differentiate members of the Enterobacteriaceae family (D)</p> Signup and view all the answers

Which sugar in triple sugar iron agar is used to detect hydrogen sulfide production?

<p>Glucose (B)</p> Signup and view all the answers

How does the pH indicator neutral red function in MacConkey agar?

<p>It changes color to indicate lactose fermentation (D)</p> Signup and view all the answers

What are non-coliforms in the context of MacConkey agar?

<p>Bacteria that do not ferment lactose and produce colorless colonies (C)</p> Signup and view all the answers

What indicates a lactose fermentation reaction in triple sugar iron agar?

<p>Color change of medium to yellow (C)</p> Signup and view all the answers

Flashcards

False negative in fermentation test

A false negative result in a carbohydrate fermentation test occurs if the test is read later than 24 hours.

Urea Broth Purpose

A differential medium used to distinguish Proteus species from other lactose non-fermenters based on their urease production.

Urea Broth Substrate

Urea is the substrate in urea broth, which bacteria may break down with an enzyme.

Urease Test Product

Ammonia is produced when urease breaks down urea; this results in a pH increase.

Signup and view all the flashcards

Urease Test pH Indicator

Phenol red is the pH indicator in urea broth, changing color to indicate urease activity.

Signup and view all the flashcards

Urease Test Enzyme

Urease is the enzyme that bacteria use to break down urea, tested in urea broth.

Signup and view all the flashcards

Positive Urease Test

A bright pink color in urea broth indicates a positive urease test (bacteria produce urease rapidly).

Signup and view all the flashcards

Negative Urease Test Results

A negative urease test shows the broth retaining its original colour or turning slightly yellow, showing slower or no urease production in the bacteria.

Signup and view all the flashcards

MacConkey agar: Function

A selective and differential medium used to isolate and differentiate Gram-negative enteric bacteria based on their ability to ferment lactose.

Signup and view all the flashcards

MacConkey agar: Selective Agent

Bile salts and crystal violet in MacConkey agar inhibit the growth of Gram-positive bacteria and some non-enteric Gram-negative bacteria.

Signup and view all the flashcards

MacConkey agar: Substrate

Lactose is the primary substrate in MacConkey agar. Bacteria that can ferment lactose produce acid, leading to a color change in the pH indicator.

Signup and view all the flashcards

MacConkey agar: pH Indicator

Neutral red is the pH indicator in MacConkey agar. It turns pink/red in the presence of acid, indicating lactose fermentation.

Signup and view all the flashcards

MacConkey agar: Coliforms

Coliforms are bacteria that ferment lactose and produce acid. Their colonies appear pink/red on MacConkey agar.

Signup and view all the flashcards

MacConkey agar: Non-coliforms

Non-coliforms do not ferment lactose and therefore produce colorless colonies on MacConkey agar.

Signup and view all the flashcards

Triple Sugar Iron agar: Purpose

A differential medium that distinguishes members of the Enterobacteriaceae family based on their ability to ferment glucose, lactose, and sucrose, produce gas, and/or generate hydrogen sulfide (H2S).

Signup and view all the flashcards

Triple Sugar Iron agar: Substrates

Triple Sugar Iron agar contains glucose, lactose, and sucrose as substrates. Each sugar can be fermented by different bacteria, producing acid and gas.

Signup and view all the flashcards

Indole Test Purpose

Identifies bacteria that can produce the enzyme tryptophanase, which breaks down the amino acid tryptophan into indole.

Signup and view all the flashcards

Indole Test Substrate

The substrate in the indole test is tryptophan, an amino acid.

Signup and view all the flashcards

Indole Test Detectable Product

The detectable product in the indole test is indole, produced by the breakdown of tryptophan.

Signup and view all the flashcards

Indole Test Reagent

Kovac's reagent is added to the culture medium to react with indole, forming a red ring at the surface.

Signup and view all the flashcards

Methyl Red Test Purpose

Detects bacteria that produce large amounts of acids through the mixed acid fermentation pathway.

Signup and view all the flashcards

Methyl Red Test Substrate

Glucose is the substrate in the methyl red test, metabolized via fermentation.

Signup and view all the flashcards

Methyl Red Test Detectable Product

The presence of acid (e.g., lactic acid, acetic acid) is detected, lowering the pH of the medium.

Signup and view all the flashcards

Methyl Red Test Reagent

Methyl red, a pH indicator, turns red in acidic environments, indicating a positive test result.

Signup and view all the flashcards

Voges-Proskauer Test Purpose

Detects bacteria that utilize the 2,3 butanediol fermentation pathway by detecting acetoin, an intermediate product.

Signup and view all the flashcards

Voges-Proskauer Test Substrate

Glucose is the substrate utilized in the Voges-Proskauer test.

Signup and view all the flashcards

Voges-Proskauer Test Detectable Product

Acetoin, an intermediate product of the 2,3 butanediol fermentation pathway, is detected.

Signup and view all the flashcards

Voges-Proskauer Test Reagents

VP reagent A (alpha-naphthol) and VP reagent B (potassium hydroxide) are used to detect acetoin.

Signup and view all the flashcards

Citrate Hydrolysis Test Purpose

Detects bacteria that can utilize citrate as a source of carbon and energy when other nutrients are absent.

Signup and view all the flashcards

Citrate Hydrolysis Test Medium

Simmons' citrate agar, a selective and differential medium, is used.

Signup and view all the flashcards

Citrate Hydrolysis Test Substrate

Citrate is the substrate in this test, used as a carbon source by some bacteria.

Signup and view all the flashcards

Citrate Hydrolysis Test Products

Alkaline products (like ammonia) are produced, raising the pH of the medium, indicating a positive result.

Signup and view all the flashcards

Citrate Hydrolysis Test Indicator

Bromthymol blue, a pH indicator, changes color when the medium becomes alkaline, indicating a positive test result.

Signup and view all the flashcards

Indole Test Enzyme

Tryptophanase is the enzyme detected by the indole test.

Signup and view all the flashcards

Citrate Hydrolysis Test Enzyme

Citrase is the enzyme detected in the citrate hydrolysis test.

Signup and view all the flashcards

Study Notes

Lancefield Grouping and Hemolysis Testing

  • Differentiates streptococci and enterococci into groups A-T
  • Based on carbohydrate composition of antigens on cell wall surfaces
  • Group A: Streptococcus pyogenes
  • Group B: Streptococcus agalactiae
  • Group D: various streptococci and enterococci

Bacitracin and Optochin Sensitivity Testing

  • Bacitracin test: differentiates Group A (Streptococcus pyogenes) from Group B (Streptococcus agalactiae)
    • Grow bacteria on blood agar
    • Place bacitracin disc on agar
    • Check for clear zone (zone of inhibition)
    • 10mm zone = sensitive; no zone = resistant
  • Optochin test: distinguishes Streptococcus pneumoniae(sensitive) from other alpha-hemolytic streptococci like Streptococcus viridans(resistant)
    • Grow bacteria on blood agar
    • Place optochin disc on agar
    • Look for zone of inhibition
    • Zone = sensitive; no zone = resistant

Bile Esculin Agar

  • Selective and differential medium
  • Separates Group D streptococci and enterococci from other streptococci
  • Selective ingredient: bile (inhibits most non-group D organisms)
  • Differential ingredient: esculin (a sugar compound that certain Group D streptococci can chemically alter)
  • Color indicator: dark brown/black iron precipitate forms when esculin is broken down

6.5% Salt Broth

  • Selective medium
  • High sodium chloride concentration
  • Selects for enterococci (like Enterococcus faecalis) and against other bacteria.

MacConkey Agar

  • Selective and differential medium for Enterobacteriaceae
  • Selective ingredient: bile salts (inhibits gram-positive bacteria)
  • Differential ingredient: lactose (color indicator shows if lactose is fermented)
    • Pink/red colonies = acidic pH (fermented lactose)
    • Colorless colonies = neutral pH (did not ferment lactose)

Triple Sugar Iron Agar (TSIA)

  • Differential medium for Enterobacteriaceae
  • Differentiates based on fermentation of sugars (glucose, lactose, sucrose) and production of hydrogen sulfide (H2S)
    • Yellow slant + yellow butt = glucose fermentation
    • Red slant + yellow butt = glucose fermentation only
    • Red slant + red butt = no fermentation
    • Black precipitate in butt = H2S production

Urea Broth

  • Differential medium, distinguishes Proteus from other lactose non-fermenters
  • Detects urease (enzyme that degrades urea)
  • Positive result = pink color indicates ammonia production and alkaline pH.

Indole Test (Tryptone Broth)

  • Differentiates bacteria based on their ability to produce tryptophanase (breaks down tryptophan).
  • Positive = red ring after adding Kovac's reagent.

Methyl Red Test (MR-VP Broth)

  • Detects mixed acid fermentation products (acidic pH).
  • Positive = red color.

Voges-Proskauer Test (MR-VP Broth)

  • Detects 2,3-butanediol fermentation products
  • Positive result = red color

Citrate Test (Simmon's Citrate Agar)

  • Differentiates bacteria based on their ability to use citrate as a sole carbon source.
  • Positive result = blue color due to alkalinity.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Microbio Lab Exam 2 (Labs 24-29) PDF

Description

Test your knowledge on Lancefield grouping and hemolysis testing in streptococci and enterococci. This quiz covers key concepts such as bacitracin and optochin sensitivity testing, along with the use of bile esculin agar. Perfect for microbiology students and enthusiasts!

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser