Podcast
Questions and Answers
What is the first step a pathogen must take to cause disease?
What is the first step a pathogen must take to cause disease?
- Damage host tissues
- Evade host defenses
- Adhere to host tissues
- Gain access to the host (correct)
Which of the following is NOT classified as a portal of entry for pathogens?
Which of the following is NOT classified as a portal of entry for pathogens?
- Mucous membranes
- Skin
- Nervous system (correct)
- Respiratory tract
What does the term 'infectious dose (50%)' or ID50 refer to?
What does the term 'infectious dose (50%)' or ID50 refer to?
- The number of organisms necessary for infection in 50% of hosts (correct)
- The average count of bacteria in a chronic infection
- The total number of pathogens required for disease symptoms
- The number of organisms needed to kill 50% of a population
Which component acts as a barrier to phagocytosis for pathogens like S.pneumoniae?
Which component acts as a barrier to phagocytosis for pathogens like S.pneumoniae?
Which of the following toxins is noted for its extremely low lethal dose (LD50)?
Which of the following toxins is noted for its extremely low lethal dose (LD50)?
What role do adhesins play in the process of microbial pathogenesis?
What role do adhesins play in the process of microbial pathogenesis?
Which mechanism is used by pathogens for antigenic variation?
Which mechanism is used by pathogens for antigenic variation?
What are biofilms primarily composed of?
What are biofilms primarily composed of?
What is one method by which pathogens can directly damage host tissues?
What is one method by which pathogens can directly damage host tissues?
What type of toxins are exotoxins primarily associated with?
What type of toxins are exotoxins primarily associated with?
Which of the following is a common portal of exit for pathogens?
Which of the following is a common portal of exit for pathogens?
How do endotoxins typically affect the host organism?
How do endotoxins typically affect the host organism?
Infection induced by which of the following typically signals that a pathogen is present?
Infection induced by which of the following typically signals that a pathogen is present?
What is a characteristic feature of exotoxins compared to endotoxins?
What is a characteristic feature of exotoxins compared to endotoxins?
Which of the following is a consequence of high concentrations of endotoxins in the bloodstream?
Which of the following is a consequence of high concentrations of endotoxins in the bloodstream?
Which type of bacterial toxin is primarily responsible for tissue septicity in Gram-negative infections?
Which type of bacterial toxin is primarily responsible for tissue septicity in Gram-negative infections?
Flashcards
Portal of Entry
Portal of Entry
The path a pathogen uses to enter the host's body, such as the respiratory, gastrointestinal, or genitourinary tracts, skin openings, or parenteral route.
Infectious Dose (ID50)
Infectious Dose (ID50)
The minimum number of pathogens required to establish an infection in 50% of exposed hosts.
Adherence
Adherence
The ability of a pathogen to attach to host cells using adhesins (on the pathogen) that bind to receptors on host cells.
Capsule (glycocalyx)
Capsule (glycocalyx)
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Exoenzyme
Exoenzyme
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Antigenic Variation
Antigenic Variation
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Infectious Dose
Infectious Dose
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Lethal Dose (LD50)
Lethal Dose (LD50)
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Exotoxins
Exotoxins
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Endotoxins
Endotoxins
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Bacterial Damage Mechanisms
Bacterial Damage Mechanisms
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A-B Toxins
A-B Toxins
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Septic Shock
Septic Shock
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Bacterial Pathogenicity
Bacterial Pathogenicity
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Virulence Plasmids
Virulence Plasmids
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Lysogenic Conversion
Lysogenic Conversion
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Study Notes
Microbial Mechanisms of Pathogenesis
- Pathogens must gain access to a host, adhere to host tissues, and penetrate/evade host defenses to cause disease.
- Portal of Entry:
- Mucous membranes (respiratory, gastrointestinal, genitourinary, conjunctiva)
- Skin
- Parenteral route (punctures, injections, bites, surgery)
- Preferred portal is prerequisite for disease, often determined by Table 15.1 on page 425.
- Adherence:
- Adhesins (molecules on microbes; glyco/lipoproteins) bind to receptors (host surface molecules; sugars)
- Biofilms are communities of microbes (e.g., dental plaque, algae, shower scum) that work together.
Damage to Host Cells
-
Pathogens commonly use host nutrients (mainly iron) to generate cellular damage.
- Siderophores are iron-scavenging proteins used by pathogens.
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Several methods of direct damage include rupture of cells after invasion and spread to other tissues.
- Cell damage may also lead to the spread of toxins.
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Toxins (Fig 15.4, page 431):
- Exotoxins (G+):
- Proteins produced inside pathogenic bacteria (mostly gram-positive).
- Released during log phase.
- Inhibit cellular functions specifically within the infected tissue.
- The host produces antitoxins for immunity.
- A-B toxins are a category of exotoxins (see Figure 15.5).
- Endotoxins (LPS Lipids):
- Lipid portions of lipopolysaccharides (LPS) found in the outer membrane of gram-negative bacteria.
- Released when bacterial cells die/breakdown.
- Produce general effects in the host, such as fever, weaknesses, aches and shock.
- Stable, so they can survive autoclaving.
- Exotoxins (G+):
Other Bacterial Causes of Pathogenicity
- Plasmids:
- R factors are a type of plasmid.
- Virulent plasmids (confer virulence)
- Bacteriophage (bacteriophages)=lysogemy: Bacteriophages can cause lysogenic conversion where the infection only becomes pathogenic when the host cell is infected by lysogenic viruses.
Pathogenicity of Other Microbes
- Viruses: intracellular parasites; cytopathic effects
- Fungi: produce toxins that cause infection
- Protozoa: presence alone signals infection
- Helminths: (worms)
- Algae: Produce neurotoxins
Portal of Exit
- Generally, the portal of exit reflects the initial portal of entry
- Common exit portals: gastrointestinal tract, genitourinary tract, respiratory tract, and conjunctiva.
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Description
Explore the intricate processes by which pathogens invade hosts and cause disease. This quiz covers the portals of entry, adherence mechanisms, and methods pathogens use to damage host cells. Test your knowledge on the fundamental concepts of microbial pathogenesis.
