Microbiology and Resident Flora
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Questions and Answers

What is the primary benefit of commensal microorganisms in the human body?

  • They benefit from the body temperature, moisture, and debris material (correct)
  • They help in the synthesis of vitamins
  • They prevent colonization by pathogenic bacteria
  • They cause disease via the respiratory tract

    • Which of the following microorganisms is an example of a mutualistic relationship in the human body?

  • Mycobacterium tuberculosis
  • Lactobacilli (correct)
  • Gonococci
  • Clostridia

    • What is the primary factor that affects the survival of microorganisms in the air?

  • Resistance to dryness
  • Existence of organic material
  • Moisture levels
  • All of the above (correct)

    • What is the role of soil microorganisms in biotransformation?

    <p>They are involved in nitrogen, sulphur, and carbon transformation</p> Signup and view all the answers

    Which of the following microorganisms is transmitted via soil?

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

    What is the primary characteristic of microorganisms in the outer environment?

    <p>They are found temporarily or permanently in certain environments</p> Signup and view all the answers

    Which of the following is a characteristic of microorganisms that survive in the air?

    <p>They are resistant to dryness</p> Signup and view all the answers

    What is the role of Lactobacilli in the adult female vagina?

    <p>They prevent colonization by pathogenic bacteria</p> Signup and view all the answers

    What is the estimated number of microbial cells in the human gastrointestinal (GI) tract?

    <p>10^13 to 10^14 microbial cells</p> Signup and view all the answers

    What is one of the essential metabolic reactions carried out by intestinal microorganisms?

    <p>Synthesis of vitamins</p> Signup and view all the answers

    Which of the following is NOT a typical characteristic of the urinary microbiota?

    <p>More abundant and more diverse than the gut microbiota</p> Signup and view all the answers

    Which of the following genera is more abundant in women's urinary microbiota?

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

    Which of the following is a product of intestinal flora metabolism?

    <p>Gas, organic acids, and odor</p> Signup and view all the answers

    What is the primary role of the gastrointestinal (GI) tract?

    <p>Digestion of food, absorption of nutrients, and production of nutrients</p> Signup and view all the answers

    What is unique about the genus Pseudomonas in the urinary microbiota?

    <p>It has only been described in men</p> Signup and view all the answers

    What is a key factor that determines the type of microorganisms present in a specific body site?

    <p>The conditions of that body site</p> Signup and view all the answers

    What happens when the balance between microorganisms is lost?

    <p>The normal flora becomes pathogenic</p> Signup and view all the answers

    What is opportunism in the context of microorganisms?

    <p>When microorganisms cause disease by taking advantage of an opportunity</p> Signup and view all the answers

    What is the main difference between strict pathogens and opportunistic pathogens?

    <p>Strict pathogens are always associated with disease, while opportunistic pathogens are not</p> Signup and view all the answers

    What happens to the transient flora when it is removed by various factors?

    <p>It does not reform</p> Signup and view all the answers

    What is the relationship between the transient flora and the permanent flora?

    <p>The transient flora usually exists together with the permanent flora</p> Signup and view all the answers

    What can happen if the permanent flora is removed?

    <p>The transient flora may cause disease</p> Signup and view all the answers

    What is a characteristic of most members of the transient flora?

    <p>They are usually nonpathogenic or opportunistic pathogens</p> Signup and view all the answers

    What is the main limitation of Koch's Postulates in modern times?

    <p>All of the above</p> Signup and view all the answers

    What is the term for microorganisms that are present on the body of healthy individuals?

    <p>Normal flora</p> Signup and view all the answers

    What is the main reason why Koch's Postulates are not applicable to viral diseases?

    <p>Viruses cannot be cultured in the same way as bacteria</p> Signup and view all the answers

    What is the main function of normal flora in the human body?

    <p>Surviving on the body</p> Signup and view all the answers

    What is the term for microorganisms that are not always present on the body but can colonize it temporarily?

    <p>Transient flora</p> Signup and view all the answers

    What is the main limitation of using Koch's Postulates to establish causality in complex diseases?

    <p>The presence of multiple causative agents</p> Signup and view all the answers

    What is the term for microorganisms that are present in the environment and can colonize the human body?

    <p>Soil microbial flora</p> Signup and view all the answers

    What is the main adaptation of Koch's Postulates in modern times?

    <p>Molecular Koch's Postulates</p> Signup and view all the answers

    Which of the following bacteria can be transmitted via contaminated water?

    <p>Salmonella typhi</p> Signup and view all the answers

    What is the role of the skin as an organ in relation to microorganisms?

    <p>It serves as a physical barrier to prevent the invasion of pathogens</p> Signup and view all the answers

    Which of the following viruses is transmitted via contaminated water?

    <p>Hepatitis A virus</p> Signup and view all the answers

    What type of disease can result from a broken skin barrier or an imbalance between commensals and pathogens?

    <p>Both skin and systemic disease</p> Signup and view all the answers

    Which of the following microorganisms is NOT transmitted via contaminated water?

    <p>Bacillus anthracis</p> Signup and view all the answers

    What type of microorganisms can be found in purified water sources?

    <p>Both pathogenic and commensal microorganisms</p> Signup and view all the answers

    Which of the following microorganisms is classified as a protozoa?

    <p>Entomoeba histolytica</p> Signup and view all the answers

    Why is the skin's physical barrier important for human health?

    <p>It prevents the invasion of pathogens</p> Signup and view all the answers

    Study Notes

    Physiological Factors Affecting Survival

    • pH levels in different parts of the body affect survival
    • Moisture levels play a crucial role in survival
    • Temperature and nutrient availability are essential for survival
    • Natural inhibitory substances also influence survival

    Resident Flora

    • Consists of a relatively fixed type of microorganisms regularly found in a given area at a given age
    • Members of the normal flora can become pathogenic if:
      • Removed from their environment and introduced into the bloodstream or tissues
      • The balance between microorganisms is lost
      • The host immune system is weakened
    • Opportunistic pathogens: members of the normal flora that cause disease when given the opportunity
      • Examples: Staphylococcus aureus, Candida albicans
    • Strict pathogens: always associated with disease

    Transient Flora

    • Consists of microorganisms that inhabit the body surface or mucous membranes for a limited period
    • Establish themselves briefly for colonization without disease
    • Removed by various factors, and does not reform; a new flora is replenished
    • The type of microorganisms in a certain body site depends on the conditions of that body site
    • Usually exists together with the permanent flora
    • If the permanent flora is removed, transient flora may cause disease
    • Most members are non-pathogenic or opportunistic pathogens

    Role of Flora in the Organism

    • Most microorganisms of the flora are commensals, benefiting from body temperature, moisture, and debris material without harming the human body
    • Some microorganisms are mutualistic, helping in:
      • Vitamin synthesis
      • Preventing colonization by pathogenic bacteria via competition

    Flora of Outer Environment

    • Microorganisms found temporarily or permanently in certain environments:
      • Air
      • Soil
      • Water
    • Air is not suitable for the growth and survival of microorganisms
    • Microorganisms diffuse into the environment via air flow
    • Survival of microorganisms on dust particles or water droplets depends on:
      • Resistance to dryness
      • Existence of organic material
      • Moisture levels
      • Temperature of the environment

    Soil Microbial Flora

    • Soil is an environment where organic material and water constantly exist
    • Numerous microorganisms in the soil play an important role in biotransformation
    • Nitrogen, sulfur, and carbon transformation happens via soil microorganisms
    • Pathogenic microorganisms transmitted via soil:
      • Clostridia (C. tetani, C. perfringens)

    Normal Microflora of the Gastrointestinal Tract

    • The human gastrointestinal tract consists of:
      • Stomach
      • Small intestine
      • Large intestine
    • Responsible for digestion of food, absorption of nutrients, and production of nutrients by the indigenous microbial flora
    • Contains 10^13 to 10^14 microbial cells
    • Functions and products of intestinal flora:
      • Vitamins
      • Gas, organic acids, and odor
      • Enzymes

    Normal Microflora of Other Body Regions

    • Urogenital Tract:
      • The microbiota in urine is less abundant and less diverse than the microbiota in other sites of the body
      • Common genera: Prevotella, Escherichia, Enterococcus, Streptococcus, or Citrobacter
      • Genus Pseudomonas has only been described in men
      • Corynebacterium and Streptococcus, more abundant in women
      • Lactobacillus, more abundant in women

    Establishing the Cause of Infectious Disease

    • Koch's Postulates:
      1. Asymptomatic carriers: some pathogens can be found in healthy individuals
      2. Non-culturable organisms: some pathogens cannot be cultured in a lab
      3. Ethical concerns: the third postulate may not be ethical to satisfy for certain diseases, especially in humans
      4. Complex diseases: some diseases may have multiple contributing factors, including more than one causative agent
      5. Molecular Koch's Postulates: a set of postulates to establish causality at the genetic and molecular levels
      6. Viral diseases: Koch's Postulates were formulated before the discovery of viruses, which cannot be cultured in the same way as bacteria

    Normal Flora of the Human Body

    • Normal flora is defined as populations of microorganisms routinely found growing on the body of healthy individuals
    • Microorganisms choose a body site suitable for their growth and survive there

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    Description

    This quiz covers the factors affecting the survival of microorganisms, including physiologic factors and the characteristics of resident flora in the human body.

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