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Questions and Answers
How do intestinal bacteria help prevent colonization by pathogens?
How do intestinal bacteria help prevent colonization by pathogens?
- By forming biofilms that block pathogens.
- By enhancing the growth of pathogenic bacteria.
- By competing for attachment sites or essential nutrients. (correct)
- By producing toxins that kill all bacteria.
What role do cross-reactive antibodies play in the immune response?
What role do cross-reactive antibodies play in the immune response?
- They stimulate the production of more pathogens.
- They suppress the immune system's activities.
- They enhance pathogen attachment to cells.
- They prevent infections by reacting with unrelated pathogens. (correct)
According to the hygiene hypothesis, lack of exposure to symbiotic microorganisms in early childhood increases susceptibility to which of the following?
According to the hygiene hypothesis, lack of exposure to symbiotic microorganisms in early childhood increases susceptibility to which of the following?
- Allergic diseases. (correct)
- Infectious diseases.
- Cardiovascular diseases.
- Autoimmune disorders.
What is one effect of disturbed normal flora in the body?
What is one effect of disturbed normal flora in the body?
What is a consequence of the indiscriminate use of broad-spectrum antimicrobial agents?
What is a consequence of the indiscriminate use of broad-spectrum antimicrobial agents?
Which type of compounds do intestinal bacteria produce to inhibit or kill other bacteria?
Which type of compounds do intestinal bacteria produce to inhibit or kill other bacteria?
What is true about natural antibodies produced against components of the normal flora?
What is true about natural antibodies produced against components of the normal flora?
How do intestinal bacteria antagonize other bacteria?
How do intestinal bacteria antagonize other bacteria?
Which of the following organisms is NOT commonly associated with lower respiratory tract diseases?
Which of the following organisms is NOT commonly associated with lower respiratory tract diseases?
What is the significance of the presence of dimorphic fungi in the lower respiratory tract?
What is the significance of the presence of dimorphic fungi in the lower respiratory tract?
Which condition can result from the physical destruction of normal flora?
Which condition can result from the physical destruction of normal flora?
Which of the following organisms colonizes the outer ear most commonly?
Which of the following organisms colonizes the outer ear most commonly?
Which of the following statements about colonization in the respiratory tract is true?
Which of the following statements about colonization in the respiratory tract is true?
What factor might promote the growth of Clostridioides difficile?
What factor might promote the growth of Clostridioides difficile?
Which of the following is a potential pathogen that colonizes the outer ear?
Which of the following is a potential pathogen that colonizes the outer ear?
How can normal flora cause disease?
How can normal flora cause disease?
Which statement about normal flora is FALSE?
Which statement about normal flora is FALSE?
What can lead to an increased risk of bacterial endocarditis?
What can lead to an increased risk of bacterial endocarditis?
What is a potential consequence of bacterial synergism?
What is a potential consequence of bacterial synergism?
What can lead to the colonization of normally sterile body parts?
What can lead to the colonization of normally sterile body parts?
What is a characteristic of the normal flora's interaction with the host?
What is a characteristic of the normal flora's interaction with the host?
Which organisms are commonly found on the skin surface?
Which organisms are commonly found on the skin surface?
What percentage of healthy individuals have Clostridium perfringens isolated on their skin?
What percentage of healthy individuals have Clostridium perfringens isolated on their skin?
Which of the following fungi are found on skin surfaces, especially in moist areas?
Which of the following fungi are found on skin surfaces, especially in moist areas?
Which of the following is true regarding the hostile environment of the skin?
Which of the following is true regarding the hostile environment of the skin?
Which of these is less commonly found on the skin compared to coagulase-negative species?
Which of these is less commonly found on the skin compared to coagulase-negative species?
Which bacteria is present in virtually all humans from birth until death?
Which bacteria is present in virtually all humans from birth until death?
Which anatomical area of the genitourinary system is permanently colonized with microbes?
Which anatomical area of the genitourinary system is permanently colonized with microbes?
What is the predominant organism in the vagina shortly after birth?
What is the predominant organism in the vagina shortly after birth?
Which group of bacteria can invade the urinary tract and lead to disease when colonized transiently in the urethra?
Which group of bacteria can invade the urinary tract and lead to disease when colonized transiently in the urethra?
What changes in the microbial flora of the vagina occur with the onset of puberty?
What changes in the microbial flora of the vagina occur with the onset of puberty?
What are the most numerous organisms found in the commensal population of the anterior urethra?
What are the most numerous organisms found in the commensal population of the anterior urethra?
Which bacteria predominates in the vagina after 6 weeks of age when maternal estrogen levels decline?
Which bacteria predominates in the vagina after 6 weeks of age when maternal estrogen levels decline?
Which structure of the urinary system is expected to be sterile under normal conditions?
Which structure of the urinary system is expected to be sterile under normal conditions?
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Study Notes
Preventing Pathogen Colonization
- Normal flora competes with pathogens for attachment sites and essential nutrients.
- Intestinal bacteria produce various compounds, including fatty acids, peroxides, and bacteriocins, to inhibit or kill other bacteria.
- Production of cross-reactive antibodies occurs, enabling "natural" antibodies to block infections through recognition of pathogen components.
Hygiene Hypothesis
- Lack of exposure to beneficial microorganisms in early childhood increases susceptibility to allergic diseases.
- Inadequate interactions with gut flora and infectious agents may suppress immune system development.
Disturbance of Normal Flora
- Disturbances in normal flora can lead to infections, allowing pathogenic organisms to thrive.
- Broad-spectrum antibiotics can eliminate normal flora, enabling pathogens like Clostridioides difficile to cause infections.
Host Factors Influencing Infections
- Immune suppression and reduced gut motility can favor pathogen growth.
- Physical damage, such as chemical exposure or dental procedures, can disrupt normal flora, allowing bacteria to enter the bloodstream, increasing infection risk.
Harmful Effects of Normal Flora
- If normal flora breaches tissues such as blood or sterile body cavities, they can cause disease (e.g., E. coli causing urinary tract infections).
- Some normal flora produce substances that promote the growth of potential pathogens.
- Competition for nutrients can occur between commensal bacteria and host microbes.
Sterile Sites in the Body
- Lower respiratory tract is typically sterile, but can transiently be colonized by upper tract secretions.
- More virulent bacterial strains can inhabit the mouth and cause lower airway diseases.
Ear Microbiota
- Coagulase-negative Staphylococcus is the most common organism in the outer ear.
- Skin organisms and potential pathogens like Pseudomonas aeruginosa and S. pneumoniae may also colonize this area.
Genitourinary System Flora
- Only the anterior urethra and vagina are permanently colonized with microbes.
- Other structures in the urinary system are usually sterile unless disease or abnormalities are present.
Anterior Urethra Microbiota
- Common organisms include lactobacilli, streptococci, and coagulase-negative staphylococci.
- Fecal organisms can transiently colonize the urethra, posing a risk for urinary tract infections.
Vaginal Microbiota Changes
- Vaginal microbiota is influenced by hormonal factors, with lactobacilli predominating in newborn girls and women of childbearing age.
- Changes in flora occur with hormonal fluctuations, introducing other bacterial taxa such as staphylococci and Enterobacteriaceae.
Skin Microbiota
- Skin surface supports primarily Gram-positive bacteria, including coagulase-negative staphylococci and corynebacteria.
- Fungi like Candida and Malassezia are common, particularly in moist areas, highlighting the complex ecology of skin microbiota.
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