Lab -7: Enterobacteriaceae Classification and Characteristics
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Questions and Answers

What distinguishes Klebsiella colonies on MacConkey agar?

  • Green colonies with black centers
  • Glistening, mucoid character (correct)
  • Pink colonies due to lactose fermentation
  • Colorless colonies
  • Which agar is commonly used for the primary isolation of Salmonella?

  • Hektoen Enteric Agar
  • MacConkey Agar
  • Blood Agar (correct)
  • Eosin Methylene Blue (EMB) Agar
  • Which test is commonly used for the selective recovery of Salmonella from stool culture?

  • Urease Test
  • Salmonella-Shigella (SS) Agar (correct)
  • Oxidase Test
  • Triple Sugar Iron (TSI) Agar Test
  • What distinguishes Shigella colonies on SS agar?

    <p>Colorless colonies</p> Signup and view all the answers

    Which member of the Enterobacteriaceae family shares the ability to swarm over the surface of media?

    <p>Proteus mirabilis</p> Signup and view all the answers

    Enterobacteriaceae is a large diverse family of bacteria commonly referred to as the ______ rods

    <p>Gram-negative</p> Signup and view all the answers

    Enterobacteriaceae bacteria are normal flora of the ______ tract of humans and animals

    <p>intestinal</p> Signup and view all the answers

    Genus and species designations are based on ______ characteristics, such as patterns of carbohydrate fermentation

    <p>phenotypic</p> Signup and view all the answers

    The genera containing the species most virulent for humans( true pathogens) are: Escherichia, Shigella, Salmonella, Klebsiella, ______

    <p>Yersinia</p> Signup and view all the answers

    If motile, Enterobacteriaceae bacteria possess a ______ arrangement of flagella

    <p>peritrichous</p> Signup and view all the answers

    Most strains of E coli ferment ______ rapidly

    <p>lactose</p> Signup and view all the answers

    Klebsiella colonies on MacConkey agar have a glistening, mucoid character due to the presence of a polysaccharide ______

    <p>capsule</p> Signup and view all the answers

    Salmonella usually produce non-hemolytic smooth white colonies on ______ Agar

    <p>Blood</p> Signup and view all the answers

    Shigella do not ferment ______ or produce hydrogen sulfide gas

    <p>lactose</p> Signup and view all the answers

    Proteus mirabilis and Proteus vulgaris share the ability to swarm over the surface of ______, rather than remaining confined to discrete colonies

    <p>media</p> Signup and view all the answers

    Study Notes

    Enterobacteriaceae Overview

    • Enterobacteriaceae is a large and diverse family of bacteria known as Gram-negative rods.
    • These bacteria can ferment sugars, classifying them as fermentative.
    • They are considered enteric bacilli, typically found as normal flora in the intestinal tracts of humans and animals.

    Classification

    • Classification is based on phenotypic characteristics, particularly patterns of carbohydrate fermentation.
    • Major genera containing the most virulent species for humans include:
      • Escherichia
      • Shigella
      • Salmonella
      • Klebsiella
      • Yersinia
    • Additional medically important but less common genera are:
      • Enterobacter
      • Serratia
      • Proteus
      • Morganella
      • Providencia

    Common Characteristics

    • Bacteria in the Enterobacteriaceae family are gram-negative rods.
    • If motile, they typically have a peritrichous arrangement of flagella; exceptions include non-motile Shigella and Klebsiella.
    • They are facultative anaerobes, capable of surviving in both aerobic and anaerobic environments.
    • Enterobacteriaceae are oxidase negative.
    • All species ferment glucose, although they exhibit significant variability in other biochemical characteristics.

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    Description

    This quiz covers the definition, classification, and characteristics of Enterobacteriaceae, a family of Gram-negative, fermentative bacteria commonly found in the intestinal tract of humans and animals. It includes information on genus and species designations based on phenotypic characteristics.

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