MCQ on Blood Agar

Sourav Bio

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  1. Answer Key

Blood agar is a type of agar plate used in microbiology to grow and isolate microorganisms, particularly bacteria. It is made by adding sterile blood to the agar base, which typically consists of peptones, beef extract, and agar. The blood can come from various sources, such as sheep, horse, or human, and is typically heated to kill any potentially contaminating microorganisms. Blood agar is used for the identification and differentiation of bacteria based on their ability to grow on the media and produce certain enzymes or toxins that result in the alteration of the media. It is also used to evaluate the hemolytic activity of certain bacteria, which is the ability of the bacteria to lyse red blood cells and produce a characteristic zone of clearing on the agar surface. Blood agar is used in both clinical and research settings for the cultivation and identification of microorganisms.

  1. What is the purpose of using blood agar in microbiological culture?
    • a) To identify bacteria
    • b) To differentiate bacteria
    • c) To isolate bacteria
    • d) All of the above
  2. Which of the following nutrients is not present in blood agar?
    • a) Hemoglobin
    • b) Peptones
    • c) Lipids
    • d) Sodium chloride
  3. Which of the following microorganisms does not grow well on blood agar?
    • a) Streptococcus pneumoniae
    • b) Staphylococcus aureus c) Neisseria gonorrhoeae d) Escherichia coli
  4. What is the significance of hemolysis on blood agar?
    • a) It indicates the presence of toxins produced by certain bacteria
    • b) It indicates the presence of enzymes produced by certain bacteria
    • c) It indicates the absence of certain nutrients
    • d) It has no significance
  5. Which of the following is not a type of hemolysis on blood agar?
    • a) Alpha hemolysis
    • b) Beta hemolysis
    • c) Gamma hemolysis
    • d) Delta hemolysis
  6. How is blood agar typically inoculated?
    • a) By streaking the surface with a bacterial culture
    • b) By stabbing the agar with a needle
    • c) By pouring a liquid bacterial culture onto the agar
    • d) By spreading the bacterial culture with a cotton swab
  7. What is the optimal temperature for culturing microorganisms on blood agar?
    • a) 4°C
    • b) 22°C
    • c) 37°C
    • d) 45°C
  8. What is the optimal pH for blood agar?
    • a) 4.5
    • b) 6.0
    • c) 7.5
    • d) 9.0
  9. What is the shelf life of blood agar?
    • a) 1 week
    • b) 2 weeks
    • c) 1 month
    • d) 2 months
  10. Can blood agar be used for anaerobic culturing?
    • a) Yes
    • b) No
    • c) It depends on the microorganism being cultured
    • d) It depends on the conditions of the culturing environment

Answer Key

  1. d) All of the above
  2. c) Lipids
  3. d) Escherichia coli
  4. a) It indicates the presence of toxins produced by certain bacteria
  5. d) Delta hemolysis
  6. a) By streaking the surface with a bacterial culture
  7. c) 37°C
  8. c) 7.5
  9. c) 1 month
  10. b) No


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