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Questions and Answers
What is the diameter of Corynebacteria?
What is the diameter of Corynebacteria?
Which granules are mainly composed of high molecular weight polyphosphate?
Which granules are mainly composed of high molecular weight polyphosphate?
Which granules are stained deep blue and found in the cytoplasm?
Which granules are stained deep blue and found in the cytoplasm?
How do individual Corynebacteria in stained smears typically appear?
How do individual Corynebacteria in stained smears typically appear?
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What is a characteristic appearance of Corynebacteria?
What is a characteristic appearance of Corynebacteria?
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Which method is not used for bacteriological diagnosis?
Which method is not used for bacteriological diagnosis?
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What type of examination involves the use of a microscope?
What type of examination involves the use of a microscope?
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Which of these sugars is not fermented by C. diphtheriae?
Which of these sugars is not fermented by C. diphtheriae?
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Which type of bacteria is Corynebacterium?
Which type of bacteria is Corynebacterium?
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Where is Corynebacterium commonly found?
Where is Corynebacterium commonly found?
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Which biochemical property is true for C. diphtheriae?
Which biochemical property is true for C. diphtheriae?
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C. diphtheriae ferments which of the following with acid production?
C. diphtheriae ferments which of the following with acid production?
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What is a common contaminant of clinical specimens that Corynebacterium is known for?
What is a common contaminant of clinical specimens that Corynebacterium is known for?
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What severe disease can the exotoxin produced by Corynebacterium cause?
What severe disease can the exotoxin produced by Corynebacterium cause?
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For what purpose is Corynebacterium often submitted?
For what purpose is Corynebacterium often submitted?
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What is the initial appearance of C. diphtheriae colonies on Löffler's medium?
What is the initial appearance of C. diphtheriae colonies on Löffler's medium?
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Which of these characteristics is true regarding the C. diphtheriae colonies on blood agar?
Which of these characteristics is true regarding the C. diphtheriae colonies on blood agar?
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What is a characteristic of C. diphtheriae colonies as they evolve on Löffler's medium?
What is a characteristic of C. diphtheriae colonies as they evolve on Löffler's medium?
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What is one of the criteria used to classify the four biotypes of C. diphtheriae?
What is one of the criteria used to classify the four biotypes of C. diphtheriae?
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Which of the following is NOT a recognized biotype of C. diphtheriae?
Which of the following is NOT a recognized biotype of C. diphtheriae?
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Study Notes
Morphology and Identification
- Corynebacteria are 0.5-1 µm in diameter, non-motile, and do not have capsules.
- They have an irregular shape, appearing "club-shaped" due to the presence of granules at one end.
- They are carotenoid-positive and have irregularly distributed granules within the cell.
- Metachromatic granules or Babes-Ernst granules are composed of high molecular weight polyphosphate and can be present at one or both ends of the cell.
- Volutin granules stain deep blue and are found in the cytoplasm.
- Stained smears of corynebacteria often show parallel or acute angles between individual cells.
Diagnostic Laboratory Tests
Characterizations of C. diphtheriae
- C. diphtheriae grows poorly on Löffler's medium, leading to pleomorphism and distinct morphology.
- Colonies on Löffler's medium are small, opaque, white, and circular with a regular border that later becomes crenated and elevated with a yellow center.
- On blood agar, colonies are small, granular, and gray with irregular edges, and may have small zones of hemolysis.
- There are four recognized biotypes of C. diphtheriae: gravis, mitis, intermedius, and belfanti, classified based on growth characteristics, biochemical reactions, and disease severity.
Diagnostic Laboratory Tests
- Sterile swabs are taken from the lesion site and can include a portion of the pseudomembrane.
- Bacteriological diagnosis methods include smear examination, cultural examination, and pathogenicity tests.
Biochemical Reactions
- C. diphtheriae ferments glucose, galactose, maltose, and dextrin with acid production.
- It does not ferment lactose, sucrose, or mannitol.
- It does not liquefy gelatin.
- It is H2S-positive and catalase-positive.
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