20 Questions
What defines a microorganism as a pathogen?
Its ability to cause disease in healthy persons with normal immune defenses
Which type of pathogens rarely cause disease in immunocompetent people but can cause serious infections in immunocompromised patients?
Opportunistic pathogens
What is the 50% lethal dose (LD50) a measure of?
The number of organisms needed to kill half the hosts
What are virulence factors responsible for?
Infecting or damaging host tissues
Which type of toxin can cause disease even in the absence of the microorganism itself?
Exotoxins
Which component of AB exotoxins is responsible for the toxic effects?
A subunit
Which disease is caused by an exotoxin that prevents the release of inhibitory neurotransmitter glycine?
Tetanus
Which disease is caused by an exotoxin that triggers cAMP production and causes severe diarrhea and dehydration if left untreated?
Cholera
What type of exotoxins can make protein channels in the plasma membrane and kill various immune cells?
Membrane-disrupting toxins
Which type of exotoxins stimulate a wide immune response by binding to major histocompatibility complex (MHC) class II molecules?
Superantigens
Which type of bacteria most commonly secretes exotoxins?
Gram-negative bacteria
What is the primary function of the B subunit in AB exotoxins?
To bind to specific target cells
Which of the following refers to the ability of bacteria to spread to adjacent tissues through active or passive means?
Invasiveness
What are the critical determinants in overpowering the host during infectious diseases?
The number of organisms and their virulence
What is the term for specific toxins produced by bacteria, which can have local or systemic effects?
Toxicity
Which mechanism involves the production of capsules, biofilms, toxins, degradative enzymes, and resistance to antibiotics by bacteria?
Bacterial virulence
What are exoenzymes produced by pathogens that enable them to invade host cells and deeper tissues?
Glycohydrolases
Which type of pathogens can cause disease through invasiveness, toxicity, and immunopathology?
Bacteria
What is the term for the ability of pathogens to escape from the body's immune system?
Immunosuppression
'Exoenzymes' are primarily involved in which bacterial function?
'Invasiveness'
Study Notes
- Staphylococcus aureus virulence factors include molecules synthesized by the bacteria or acquired from the environment
- Virulence factors enable the bacteria to cause damage to the host through various functions: colonization, immune escape, immunosuppression, cellular entry and exit, and nutrient extraction
- People get infectious diseases when the balance between the organism and the host shifts in favor of the organism
- Critical determinants in overpowering the host are the number of organisms and their virulence
- Pathogens can enter the body through various portals of entry, including mucous membranes, respiratory and gastro-intestinal tracts, genitourinary tract, conjunctiva, skin, and parenteral route
- Transmission of infectious diseases can occur through fecal-oral contact, wounds, burns, contact with animals or humans, and vectors
- Bacterial virulence mechanisms include the production of capsules, biofilms, toxins, degradative enzymes, and resistance to antibiotics
- Pathogens can cause disease through toxicity, invasiveness, and immunopathology
- Toxicity refers to specific toxins produced by bacteria, which can have local or systemic effects
- Invasiveness involves the ability of bacteria to spread to adjacent tissues through active or passive means, and the production of specific products and/or enzymes that promote spreading
- Exoenzymes are extracellular enzymes produced by pathogens that enable them to invade host cells and deeper tissues, and have a wide variety of targets
- Different classes of exoenzymes include glycohydrolases, nucleases, and proteases, each with specific targets
- Staphylococcus aureus is an example of a bacterium that causes systemic infections and is able to proliferate, disseminate, and destroy tissues, and produces various toxins and enzymes for virulence.
Test your knowledge on the principles of pathogenesis and the characteristics of pathogenic microorganisms. Learn about true pathogens and opportunistic pathogens, and their ability to cause disease in humans with different levels of immune defenses.
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