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Questions and Answers
Which of the following is NOT a mechanism by which the normal microbiota contributes to health?
Which of the following is NOT a mechanism by which the normal microbiota contributes to health?
What is the term used to describe the ability of the normal microbiota to limit the growth of pathogens?
What is the term used to describe the ability of the normal microbiota to limit the growth of pathogens?
In what scenario might the normal microbiota become pathogenic?
In what scenario might the normal microbiota become pathogenic?
What is a potential consequence of antibiotic treatment that disrupts the normal microbiota?
What is a potential consequence of antibiotic treatment that disrupts the normal microbiota?
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Which of the following is an example of a substance produced by intestinal bacteria to inhibit other bacteria?
Which of the following is an example of a substance produced by intestinal bacteria to inhibit other bacteria?
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How does the normal microbiota contribute to the production of "cross-reactive antibodies"?
How does the normal microbiota contribute to the production of "cross-reactive antibodies"?
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What is a potential outcome of a weakened or disrupted normal microbiota?
What is a potential outcome of a weakened or disrupted normal microbiota?
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Which of the following statements accurately describes the relationship between the normal microbiota and the host?
Which of the following statements accurately describes the relationship between the normal microbiota and the host?
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What defines the term 'commensals' in relation to the normal microbiota?
What defines the term 'commensals' in relation to the normal microbiota?
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Which factor does NOT contribute to the temporary nature of transient microbiota?
Which factor does NOT contribute to the temporary nature of transient microbiota?
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Which statement accurately describes resident microbiota?
Which statement accurately describes resident microbiota?
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What is one of the main roles of the normal microbiota in human health?
What is one of the main roles of the normal microbiota in human health?
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How does the transient microbiota influence resident microbiota?
How does the transient microbiota influence resident microbiota?
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What is a reason that transient microbiota may not survive on the skin?
What is a reason that transient microbiota may not survive on the skin?
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Which of the following statements is true concerning the competition between resident and transient microbiota?
Which of the following statements is true concerning the competition between resident and transient microbiota?
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Which characteristic is associated with the transient microbiota?
Which characteristic is associated with the transient microbiota?
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Which of the following microorganisms are predominant in the skin's normal microbiota?
Which of the following microorganisms are predominant in the skin's normal microbiota?
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What type of organism is Staphylococcus epidermidis considered in relation to the skin?
What type of organism is Staphylococcus epidermidis considered in relation to the skin?
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In which part of the skin are anaerobic organisms such as Propionibacterium typically found?
In which part of the skin are anaerobic organisms such as Propionibacterium typically found?
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Which organism is commonly implicated in the pathogenesis of acne?
Which organism is commonly implicated in the pathogenesis of acne?
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What is a common feature of the skin that affects the survival of transient bacteria?
What is a common feature of the skin that affects the survival of transient bacteria?
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Which of the following is NOT a characteristic of the predominant resident bacteria on the skin?
Which of the following is NOT a characteristic of the predominant resident bacteria on the skin?
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What is the typical microbial colonization status of the lower bronchi and alveoli?
What is the typical microbial colonization status of the lower bronchi and alveoli?
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Which species is considered a significant pathogen found in the nose?
Which species is considered a significant pathogen found in the nose?
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Which of the following is NOT a predominant organism found on the conjunctiva?
Which of the following is NOT a predominant organism found on the conjunctiva?
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Based on the information provided, which of the following statements about the normal microbiota of the small intestine is TRUE?
Based on the information provided, which of the following statements about the normal microbiota of the small intestine is TRUE?
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Which of the following is a primary factor contributing to the low bacterial population in the stomach?
Which of the following is a primary factor contributing to the low bacterial population in the stomach?
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Which of the following statements about the normal microbiota of the large intestine is FALSE?
Which of the following statements about the normal microbiota of the large intestine is FALSE?
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What is the significance of the presence of lysozyme in tears?
What is the significance of the presence of lysozyme in tears?
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Which of the following bacterial species is NOT commonly found in the small intestine?
Which of the following bacterial species is NOT commonly found in the small intestine?
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Which of the following is a key difference in the composition of the normal microbiota between bottle-fed and breast-fed infants?
Which of the following is a key difference in the composition of the normal microbiota between bottle-fed and breast-fed infants?
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Which of the following statements accurately describes the role of E. coli in the normal microbiota of the intestinal tract?
Which of the following statements accurately describes the role of E. coli in the normal microbiota of the intestinal tract?
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Which organism is primarily associated with dental plaque and caries development?
Which organism is primarily associated with dental plaque and caries development?
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What is the primary source of viridans streptococci in infants shortly after birth?
What is the primary source of viridans streptococci in infants shortly after birth?
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Which type of bacteria is most likely to be found in gingival crevices?
Which type of bacteria is most likely to be found in gingival crevices?
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What role do anaerobic spirochetes and Fusobacterium species play in oral microbiota?
What role do anaerobic spirochetes and Fusobacterium species play in oral microbiota?
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What type of microbiota is predominantly observed in the intestines of breast-fed infants?
What type of microbiota is predominantly observed in the intestines of breast-fed infants?
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What condition can result from viridans streptococci entering the bloodstream during dental procedures?
What condition can result from viridans streptococci entering the bloodstream during dental procedures?
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What characterizes the microbial population of the mouth upon the eruption of teeth?
What characterizes the microbial population of the mouth upon the eruption of teeth?
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Which of the following organisms is associated with lung abscesses if aspirated in debilitated patients?
Which of the following organisms is associated with lung abscesses if aspirated in debilitated patients?
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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.
