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Normal Human Microbiota
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Normal Human Microbiota

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@ProsperousFlugelhorn

Questions and Answers

Which of the following is NOT a mechanism by which the normal microbiota contributes to health?

  • Stimulating the production of antibodies that cross-react with pathogens
  • Occupying attachment sites to prevent colonization by pathogens
  • Producing substances that inhibit or kill non-indigenous bacteria
  • Directly attacking and destroying pathogens through immune responses (correct)

    • What is the term used to describe the ability of the normal microbiota to limit the growth of pathogens?

  • Immune suppression
  • Pathogenic interference
  • Antibiotic resistance
  • Colonization resistance (correct)

    • In what scenario might the normal microbiota become pathogenic?

  • When they are located in a different part of the body than their usual site (correct)
  • When they are introduced to a new host
  • When they are exposed to sunlight
  • When they are present in high numbers in the intestines

    • What is a potential consequence of antibiotic treatment that disrupts the normal microbiota?

    <p>Increased susceptibility to opportunistic infections</p> Signup and view all the answers

    Which of the following is an example of a substance produced by intestinal bacteria to inhibit other bacteria?

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

    How does the normal microbiota contribute to the production of "cross-reactive antibodies"?

    <p>By acting as antigens and inducing an immune response</p> Signup and view all the answers

    What is a potential outcome of a weakened or disrupted normal microbiota?

    <p>Increased susceptibility to infections</p> Signup and view all the answers

    Which of the following statements accurately describes the relationship between the normal microbiota and the host?

    <p>The normal microbiota are generally beneficial but can become harmful under certain conditions</p> Signup and view all the answers

    What defines the term 'commensals' in relation to the normal microbiota?

    <p>Organisms that derive benefit without harming the host</p> Signup and view all the answers

    Which factor does NOT contribute to the temporary nature of transient microbiota?

    <p>Ability to establish permanent colonies</p> Signup and view all the answers

    Which statement accurately describes resident microbiota?

    <p>They are fixed types of microorganisms regularly found in specific body areas.</p> Signup and view all the answers

    What is one of the main roles of the normal microbiota in human health?

    <p>They prevent microbial pathogens from thriving.</p> Signup and view all the answers

    How does the transient microbiota influence resident microbiota?

    <p>By potentially causing disease when resident microbiota are disturbed</p> Signup and view all the answers

    What is a reason that transient microbiota may not survive on the skin?

    <p>They may be washed away or flushed out.</p> Signup and view all the answers

    Which of the following statements is true concerning the competition between resident and transient microbiota?

    <p>Resident microbiota typically outcompete transient microbiota.</p> Signup and view all the answers

    Which characteristic is associated with the transient microbiota?

    <p>They are generally nonpathogenic or only potentially pathogenic.</p> Signup and view all the answers

    Which of the following microorganisms are predominant in the skin's normal microbiota?

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

    What type of organism is Staphylococcus epidermidis considered in relation to the skin?

    <p>A nonpathogen under typical conditions</p> Signup and view all the answers

    In which part of the skin are anaerobic organisms such as Propionibacterium typically found?

    <p>Dermis, in deeper follicles</p> Signup and view all the answers

    Which organism is commonly implicated in the pathogenesis of acne?

    <p>Propionibacterium acnes</p> Signup and view all the answers

    What is a common feature of the skin that affects the survival of transient bacteria?

    <p>Acidic pH</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the predominant resident bacteria on the skin?

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

    What is the typical microbial colonization status of the lower bronchi and alveoli?

    <p>Contains a low number of organisms</p> Signup and view all the answers

    Which species is considered a significant pathogen found in the nose?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    Which of the following is NOT a predominant organism found on the conjunctiva?

    <p>Streptococcus pneumoniae</p> Signup and view all the answers

    Based on the information provided, which of the following statements about the normal microbiota of the small intestine is TRUE?

    <p>The small intestine typically contains a higher number of Candida albicans than other areas of the digestive tract.</p> Signup and view all the answers

    Which of the following is a primary factor contributing to the low bacterial population in the stomach?

    <p>The highly acidic environment of the stomach</p> Signup and view all the answers

    Which of the following statements about the normal microbiota of the large intestine is FALSE?

    <p>The majority of the normal microbiota in the large intestine are aerobic bacteria.</p> Signup and view all the answers

    What is the significance of the presence of lysozyme in tears?

    <p>Lysozyme helps to prevent colonization of the conjunctiva by bacteria.</p> Signup and view all the answers

    Which of the following bacterial species is NOT commonly found in the small intestine?

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

    Which of the following is a key difference in the composition of the normal microbiota between bottle-fed and breast-fed infants?

    <p>Bottle-fed infants have a more diverse microbial population.</p> Signup and view all the answers

    Which of the following statements accurately describes the role of E. coli in the normal microbiota of the intestinal tract?

    <p>E. coli is a facultative anaerobe and can cause infections if it enters other parts of the body.</p> Signup and view all the answers

    Which organism is primarily associated with dental plaque and caries development?

    <p>Streptococcus mutans</p> Signup and view all the answers

    What is the primary source of viridans streptococci in infants shortly after birth?

    <p>Respiratory tracts of the mother and attendants</p> Signup and view all the answers

    Which type of bacteria is most likely to be found in gingival crevices?

    <p>Anaerobic Clostridium species</p> Signup and view all the answers

    What role do anaerobic spirochetes and Fusobacterium species play in oral microbiota?

    <p>They establish themselves during tooth eruption.</p> Signup and view all the answers

    What type of microbiota is predominantly observed in the intestines of breast-fed infants?

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

    What condition can result from viridans streptococci entering the bloodstream during dental procedures?

    <p>Subacute bacterial endocarditis</p> Signup and view all the answers

    What characterizes the microbial population of the mouth upon the eruption of teeth?

    <p>Establishment of anaerobic spirochetes and Fusobacterium</p> Signup and view all the answers

    Which of the following organisms is associated with lung abscesses if aspirated in debilitated patients?

    <p>Prevotella melaninogenica</p> Signup and view all the answers

    Study Notes

    Normal Human Microbiota

    • The normal microbiota consists of microorganisms that inhabit the skin and mucous membranes of healthy individuals, providing a first line of defense against microbial pathogens, assisting in digestion, and contributing to the maturation of the immune system.
    • The normal microbiota can be divided into two groups: resident microbiota and transient microbiota.

    Resident Microbiota

    • Consists of fixed types of microorganisms regularly found in a given area at a given age.
    • If disturbed, it promptly reestablishes itself.

    Transient Microbiota

    • Consists of nonpathogenic or potentially pathogenic microorganisms that inhabit the skin or mucous membranes for hours, days, or weeks.
    • Does not produce disease and does not establish itself permanently on the surface.

    Why Are These Microbes Temporary?

    • May be washed away by bathing.
    • May not be able to compete with resident normal microbiota.
    • May be killed by substances produced by the resident normal microbiota.
    • May not survive in the acidic or alkaline pH of the site.
    • May be flushed away by bodily secretions like tears, sweat, oil, urine, feces, etc.

    Role of Normal Microbiota

    • Can cause disease, especially in immunocompromised and debilitated individuals.
    • Constitutes a protective host defense mechanism by occupying attachment sites on the skin and mucosa, interfering with colonization by pathogenic bacteria.
    • Serves a nutritional function, with intestinal bacteria producing B vitamins and vitamin K.
    • Antagonizes other bacteria through the production of substances that inhibit or kill nonindigenous species.
    • Stimulates the production of "cross-reactive antibodies" against components of the normal flora, preventing infection or invasion.

    Normal Microbiota of Different Body Sites

    Skin

    • Colonized by microorganisms, most of which are harmless or even beneficial to the host.
    • Predominant resident microorganisms include:
      • Aerobic and anaerobic diphtheroid bacilli (eg, Corynebacterium, Propionibacterium).
      • Nonhemolytic aerobic and anaerobic staphylococci (Staphylococcus epidermidis).
      • Gram-positive, aerobic, spore-forming bacilli (eg, Bacillus species).
      • Hemolytic streptococci (viridans streptococci) and enterococci (Enterococcus species).

    Mouth and Upper Respiratory Tract

    • A wide spectrum of organisms colonize the nose, throat, and mouth.
    • Predominant organisms include:
      • Streptococcal and staphylococcal species (eg, S. aureus).
      • Neisseria species.
      • Viridans streptococci.
      • Anaerobic spirochetes (Prevotella species).
      • Fusobacterium species.
      • Lactobacilli.
      • Actinomyces species.
      • Protozoa.
      • Yeasts (Candida species).

    Intestinal Tract

    • At birth, the intestine is sterile, but organisms are soon introduced with food.
    • Predominant organisms include:
      • Bifidobacteria (in breast-fed children).
      • Lactobacilli.
      • Bacteroides species (99% of normal microbiota in the large intestine).
      • Escherichia coli.
      • Streptococci.
      • Yeasts (Candida albicans).

    Conjunctiva

    • Predominant organisms include:
      • Diphtheroids.
      • S. epidermidis.
      • Nonhemolytic streptococci.
      • Neisseriae.
      • Gram-negative bacilli.

    Importance of Normal Microbiota

    • Plays a significant role in extraintestinal disease, such as urinary tract infections and peritonitis.
    • Maintains a balance between health and disease.

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    Description

    Learn about the normal microbiota that inhabits the skin and mucous membranes of healthy individuals, its role in defense against pathogens, digestion, and immune system maturation.

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