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Questions and Answers
What is the defining characteristic that distinguishes pathogenicity from virulence?
What is the defining characteristic that distinguishes pathogenicity from virulence?
Which of the following is NOT considered a typical virulence factor for microbes?
Which of the following is NOT considered a typical virulence factor for microbes?
A pathogen with a low ID$_{50}$ value is considered to have which of the following properties?
A pathogen with a low ID$_{50}$ value is considered to have which of the following properties?
Which of the following is the preferred portal of entry for the development of anthrax disease caused by $Bacillus$ $anthracis$?
Which of the following is the preferred portal of entry for the development of anthrax disease caused by $Bacillus$ $anthracis$?
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How does the concept of virulence differ from the concept of pathogenicity?
How does the concept of virulence differ from the concept of pathogenicity?
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Which of the following is NOT considered a typical portal of entry for microbial pathogens?
Which of the following is NOT considered a typical portal of entry for microbial pathogens?
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What is the primary difference between pathogenicity and virulence in the context of microbial infections?
What is the primary difference between pathogenicity and virulence in the context of microbial infections?
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Which of the following is NOT considered a typical virulence factor for microbial pathogens?
Which of the following is NOT considered a typical virulence factor for microbial pathogens?
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How does the ID$_{50}$ value relate to the infectiousness of a microbial pathogen?
How does the ID$_{50}$ value relate to the infectiousness of a microbial pathogen?
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Which of the following is the preferred portal of entry for the development of anthrax disease caused by $Bacillus$ $anthracis$?
Which of the following is the preferred portal of entry for the development of anthrax disease caused by $Bacillus$ $anthracis$?
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What is the primary function of hyaluronidase in the context of pathogen virulence?
What is the primary function of hyaluronidase in the context of pathogen virulence?
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What is the primary function of IgA protease in the context of pathogen virulence?
What is the primary function of IgA protease in the context of pathogen virulence?
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Which of the following is NOT a key virulence factor related to a pathogen's ability to survive inside phagocytes?
Which of the following is NOT a key virulence factor related to a pathogen's ability to survive inside phagocytes?
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What is the primary function of antigenic variation in the context of pathogen virulence?
What is the primary function of antigenic variation in the context of pathogen virulence?
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What is the primary function of toxigenicity in the context of pathogen virulence?
What is the primary function of toxigenicity in the context of pathogen virulence?
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What is the primary function of toxoid in the context of pathogen virulence?
What is the primary function of toxoid in the context of pathogen virulence?
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What is the primary function of antitoxin in the context of pathogen virulence?
What is the primary function of antitoxin in the context of pathogen virulence?
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What is the primary function of toxemia in the context of pathogen virulence?
What is the primary function of toxemia in the context of pathogen virulence?
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What is the primary function of exotoxins and endotoxins in the context of pathogen virulence?
What is the primary function of exotoxins and endotoxins in the context of pathogen virulence?
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What is the primary mechanism by which some bacteria can produce toxins as a virulence factor?
What is the primary mechanism by which some bacteria can produce toxins as a virulence factor?
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Which term refers to the amount of toxin required to kill 50% of a population?
Which term refers to the amount of toxin required to kill 50% of a population?
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Which of the following statements about LD50 and lethality is correct?
Which of the following statements about LD50 and lethality is correct?
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Which of the following is an example of a bacterial adhesin?
Which of the following is an example of a bacterial adhesin?
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What is the function of coagulase, a bacterial enzyme?
What is the function of coagulase, a bacterial enzyme?
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Which bacterial structure is responsible for the adhesion of Streptococcus mutans?
Which bacterial structure is responsible for the adhesion of Streptococcus mutans?
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Which of the following pathogens uses hooks as adhesins?
Which of the following pathogens uses hooks as adhesins?
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What is the function of kinase, a bacterial enzyme?
What is the function of kinase, a bacterial enzyme?
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Which bacterial structure is responsible for the adhesion of Escherichia coli O157:H7?
Which bacterial structure is responsible for the adhesion of Escherichia coli O157:H7?
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Which bacterial structure is responsible for the adhesion of Streptococcus pyogenes?
Which bacterial structure is responsible for the adhesion of Streptococcus pyogenes?
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Which bacterial structure is responsible for the adhesion of Neisseria gonorrhoeae?
Which bacterial structure is responsible for the adhesion of Neisseria gonorrhoeae?
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What is the primary mechanism of action for Type II exotoxins?
What is the primary mechanism of action for Type II exotoxins?
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Which type of exotoxin is considered the most common?
Which type of exotoxin is considered the most common?
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What is the primary difference between exotoxins and endotoxins in terms of fever production?
What is the primary difference between exotoxins and endotoxins in terms of fever production?
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How are exotoxins and endotoxins typically neutralized?
How are exotoxins and endotoxins typically neutralized?
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What is the relationship between immunogens and antigens?
What is the relationship between immunogens and antigens?
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What is the primary pathogenic property of parasitic protozoa?
What is the primary pathogenic property of parasitic protozoa?
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How do parasitic protozoa typically avoid the host's immune defenses?
How do parasitic protozoa typically avoid the host's immune defenses?
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What is the primary pathogenic property of parasitic helminths (worms)?
What is the primary pathogenic property of parasitic helminths (worms)?
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Which of the following is a key difference between exotoxins and endotoxins in terms of their structural composition?
Which of the following is a key difference between exotoxins and endotoxins in terms of their structural composition?
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What is the primary portal of exit for pathogens leaving the host?
What is the primary portal of exit for pathogens leaving the host?
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Study Notes
Pathogenicity and Virulence
- Pathogenicity: the ability of a microbe/pathogen to cause disease in a host
- Virulence: the enhanced ability of a pathogen to cause infection
- Virulence factor: a characteristic or trait of the pathogen that makes it harmful, e.g., capsules, toxins, antigenic variation
Toxins
- Some bacteria can produce toxins, which can cause death of the host (lethality)
- LD50 (Lethal Dose 50): the amount of toxin required to kill 50% of the population, measures potency of a toxin
- Pathogens with low LD50 = high lethality, pathogens with high LD50 = low lethality
- Types of toxins: exotoxins, endotoxins
- Toxigenicity: the ability of a pathogen to produce a toxin
- Toxemia: the presence of toxin in the bloodstream
- Toxoid: a chemically modified toxin that is no longer toxic
- Antitoxin: an antibody against a toxin, usually injected into the host (artificial passive immunity)
Mechanisms of Pathogenicity
- Adhesion factors: ability of pathogens to attach to host tissues/cells
- Bacterial adhesins (ligands): substances on the pathogen that bind to receptors on host cells
- Types of adhesins: capsules, fimbriae, M proteins, Opa proteins, hooks
Penetration Factors (Bacterial Enzymes)
- Coagulase: helps form blood clot, stops blood flow, and prevents host defenses from reaching the bacterium
- Kinase: breaks down blood clot surrounding the bacterium, allowing it to spread throughout the body
- Hyaluronidase: breaks down hyaluronic acid in connective tissue
- Collagenase: breaks down collagen in connective tissue
- IgA protease: destroys IgA antibodies in the mucosa
Evasion of Host Defenses
- Survival inside phagocytes: pathogen escapes from phagosome before lysosomal fusion, prevents fusion of lysosome with phagosome, and resists lysosomal enzymes
- Antigenic variation: pathogen changes its surface antigens (antigenic determinants) through genetic mutations/recombination
Damage to Host Cells
- Toxins: poisonous substances (acting as antigens) produced by pathogens, can produce fever, cardiovascular problems, diarrhea, and shock
- Types of toxins: exotoxins, endotoxins
ID50 (Infectious Dose 50)
- The number of pathogens required to make 50% of the population sick
- Measures virulence of a microbe
- Infectious pathogens have different ID50's: pathogens with low ID50 = high infectiousness, pathogens with high ID50 = low infectiousness
Portals of Entry
- Mucous membranes
- Skin
- Parenteral route (non-oral entry): pathogens directly deposited into tissue or bloodstream, usually involves an "injection" into a blood vessel
Pathogenic Properties of Fungi
- Some fungal toxins can contaminate the food supply, provoke an allergic response, and are carcinogenic (cancer-causing)
Pathogenic Properties of Parasitic Protozoa
- Large number of protozoa feed on host tissue, causing damage to intestinal lining and resulting in diarrhea or dysentery
- Protozoa avoid host defenses by growing in phagocytes and antigenic variation
Pathogenic Properties of Parasitic Helminths
- Helminths = worms, not very pathogenic
- Use host's nutrients or tissues without killing the host
- Presence in the GI tract in large numbers interferes with host food absorption, leading to symptoms of fatigue and weight loss
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Description
Test your knowledge on the microbial mechanisms of pathogenicity, including concepts such as virulence, virulence factors, and portals of entry for microbes into a host. Explore how pathogens cause infectious diseases and the traits that make them harmful.
