Questions and Answers
What is the classification order of the Genus Corynebacterium?
Which scientist discovered Corynebacterium diphtheriae?
What type of bacteria is Corynebacterium considered?
What arrangement do Corynebacterium cells often display?
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Which medium was formulated by Frobisher for C. diphtheriae?
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What is the characteristic morphology of Corynebacterium?
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What is a common habitat for Corynebacterium?
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What structure do Corynebacterium cells have that contributes to Gram variability?
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What color do the granules turn when stained with Loeffler’s methylene blue?
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Where are the granules often found in bacilli?
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What is the optimum temperature for the growth of these bacilli?
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Which staining technique is NOT mentioned for demonstrating the granules?
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What type of media do these bacilli require for good growth?
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Which Corynebacterium species is resistant to 2.5% oxalic acid for one hour?
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Which property is NOT characteristic of the members discussed?
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What is a distinctive feature of the C. renale group colonies after 24 hours of incubation?
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Study Notes
Classification
- Belongs to the Kingdom Bacteria, Phylum Actinobacteria, Order Actinomycetales, Family Corynebacteriaceae, and Genus Corynebacterium.
- Notable species include Corynebacterium bovis.
History
- Genus established by Lehmann and Neumann in 1896.
- Corynebacterium diphtheriae discovered in 1884 by Edwin Klebs and Friedrich Loffler.
- Bacteriologists developed selective media for C. diphtheriae:
- Frobisher (1937) - Cystine-tellurite blood agar
- Hoyle (1941) - Hoyle’s lysed blood tellurite agar
- Tinsdale (1947) - Tinsdale agar
Introduction
- Characterized as Gram-positive, pleomorphic coccobacilli with metachromatic granules.
- Exhibit irregular staining and arrangements resembling "Chinese letters" or "V/Y" configurations.
Habitat and Ecology
- Found in soil, often in manure; commensals on mucous membranes and skin of cattle and other domestic animals.
- Chronic cases in adult animals are common carriers; many species are opportunistic pathogens.
- Persist in the intestinal tracts of horses and in the litter of stables.
Morphology
- Slender, club-shaped Gram-positive rods that are non-sporing, non-motile, and non-capsulated.
- Cell dimensions: 2 to 6 µm long and 0.5 to 1 µm in diameter.
- Stained using modified Ziehl-Neelsen (ZN) staining, results in "ballooning" and "club-shaped" cells.
Granules
- Granules consist of high-energy phosphate granules, specifically polymetaphosphate.
- Stained granules appear reddish-purple with Loeffler’s methylene blue, also known as metachromatic granules or Babes Ernst granules.
- Granules typically found at the poles of bacterial cells, referred to as polar bodies; specialized stains available for clearer visualization.
Cultural Characteristics
- Growth is slow on enriched media, resulting in small, gray colonies; requires blood, serum, or egg for optimal growth.
- Optimal growth temperature is 37ºC, with a pH of 7.2; both aerobic and facultative anaerobic.
- Some species exhibit beta-hemolysis, while others, like the renale group, are non-hemolytic.
- Highly susceptible to heat, desiccation, and disinfectants, but resistant to light and freezing.
Bio-Chemical Properties
- All species are catalase-positive; except Corynebacterium bovis, the rest are urease positive.
- Renale group shows strong urease positivity within one hour.
- Can ferment sugars, with exceptions like Rhodococcus equi; C. bovis and C. renale ferment both glucose and maltose.
- Two biotypes identified for Corynebacterium ovis.
Enhanced Hemolysis Test
- Hemolysis produced by C. pseudotuberculosis increases when inoculated across a streak of Rhodococcus equi.
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Description
Explore the fascinating world of Corynebacterium, a genus established in 1896, with a focus on notable species like C. diphtheriae. This quiz covers its classification, historical discoveries, and ecological importance in various habitats. Test your knowledge on the selective media used by bacteriologists and the unique characteristics of these Gram-positive bacteria.
