40 Questions
What is the defining characteristic that distinguishes pathogenicity from virulence?
Pathogenicity is the ability to cause disease, while virulence is the severity of the disease caused.
Which of the following is NOT considered a typical virulence factor for microbes?
Nutrient acquisition mechanisms
A pathogen with a low ID$_{50}$ value is considered to have which of the following properties?
High infectiousness
Which of the following is the preferred portal of entry for the development of anthrax disease caused by $Bacillus$ $anthracis$?
Parenteral route
How does the concept of virulence differ from the concept of pathogenicity?
Virulence describes the specific mechanisms used by a microbe to cause harm, while pathogenicity is a measure of the overall potential to cause disease.
Which of the following is NOT considered a typical portal of entry for microbial pathogens?
Digestive system
What is the primary difference between pathogenicity and virulence in the context of microbial infections?
Pathogenicity refers to the overall potential to cause disease, while virulence describes the specific mechanisms used to cause harm.
Which of the following is NOT considered a typical virulence factor for microbial pathogens?
Nutrient acquisition
How does the ID$_{50}$ value relate to the infectiousness of a microbial pathogen?
Pathogens with a low ID$_{50}$ value have high infectiousness.
Which of the following is the preferred portal of entry for the development of anthrax disease caused by $Bacillus$ $anthracis$?
Parenteral route
What is the primary function of hyaluronidase in the context of pathogen virulence?
To break down hyaluronic acid in connective tissue
What is the primary function of IgA protease in the context of pathogen virulence?
To destroy IgA antibodies in the mucosa
Which of the following is NOT a key virulence factor related to a pathogen's ability to survive inside phagocytes?
Breaking down hyaluronic acid in connective tissue
What is the primary function of antigenic variation in the context of pathogen virulence?
To change the pathogen's surface antigens through genetic mutations/recombination
What is the primary function of toxigenicity in the context of pathogen virulence?
To produce a poisonous substance (toxin) that acts as an antigen
What is the primary function of toxoid in the context of pathogen virulence?
To chemically modify a toxin so that it is no longer toxic
What is the primary function of antitoxin in the context of pathogen virulence?
To provide antibodies against a toxin, not the pathogen itself
What is the primary function of toxemia in the context of pathogen virulence?
The presence of a toxin in the bloodstream
What is the primary function of exotoxins and endotoxins in the context of pathogen virulence?
Different types of toxins produced by some bacteria
What is the primary mechanism by which some bacteria can produce toxins as a virulence factor?
Through bacterial plasmids that carry genes for toxins
Which term refers to the amount of toxin required to kill 50% of a population?
LD50
Which of the following statements about LD50 and lethality is correct?
Pathogens with a low LD50 have high lethality.
Which of the following is an example of a bacterial adhesin?
Capsules
What is the function of coagulase, a bacterial enzyme?
It helps form blood clots, preventing host defenses from reaching the bacterium.
Which bacterial structure is responsible for the adhesion of Streptococcus mutans?
Capsules
Which of the following pathogens uses hooks as adhesins?
Treponema pallidum
What is the function of kinase, a bacterial enzyme?
It breaks down blood clots surrounding the bacterium, allowing it to spread.
Which bacterial structure is responsible for the adhesion of Escherichia coli O157:H7?
Fimbriae
Which bacterial structure is responsible for the adhesion of Streptococcus pyogenes?
M proteins
Which bacterial structure is responsible for the adhesion of Neisseria gonorrhoeae?
Opa proteins
What is the primary mechanism of action for Type II exotoxins?
Disrupting the host cell membrane by forming channels or disrupting the phospholipid component
Which type of exotoxin is considered the most common?
Type III A-B Toxins
What is the primary difference between exotoxins and endotoxins in terms of fever production?
Exotoxins can cause fever, while endotoxins cannot
How are exotoxins and endotoxins typically neutralized?
Exotoxins are neutralized by antitoxin antibodies, while endotoxins are not
What is the relationship between immunogens and antigens?
Immunogens are a type of antigen that stimulate a strong immune response
What is the primary pathogenic property of parasitic protozoa?
Feeding on host tissue and damaging the intestinal lining
How do parasitic protozoa typically avoid the host's immune defenses?
By growing within phagocytic cells and undergoing antigenic variation
What is the primary pathogenic property of parasitic helminths (worms)?
They feed on the host's tissues and nutrients without killing the host
Which of the following is a key difference between exotoxins and endotoxins in terms of their structural composition?
Exotoxins are composed of proteins, while endotoxins are composed of lipids
What is the primary portal of exit for pathogens leaving the host?
The gastrointestinal tract
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
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.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
