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Questions and Answers
Which of the following diseases is NOT a zoonotic disease?
Which of the following diseases is NOT a zoonotic disease?
What is a 'fomite' in the context of disease transmission?
What is a 'fomite' in the context of disease transmission?
Which disease outbreak did Dr. John Snow famously link to a contaminated water pump?
Which disease outbreak did Dr. John Snow famously link to a contaminated water pump?
What is the primary mode of transmission for diseases like Influenza, Pneumonia, and Meningococcal infections?
What is the primary mode of transmission for diseases like Influenza, Pneumonia, and Meningococcal infections?
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How might someone contract anthrax from an animal source?
How might someone contract anthrax from an animal source?
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Which transmission method BEST describes the spread of HIV?
Which transmission method BEST describes the spread of HIV?
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Where does Legionnaires' disease often originate?
Where does Legionnaires' disease often originate?
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Trichinellosis is transmitted to humans from infected:
Trichinellosis is transmitted to humans from infected:
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Which of the following diseases are transmitted by invertebrate vectors like ticks, mosquitoes, and fleas?
Which of the following diseases are transmitted by invertebrate vectors like ticks, mosquitoes, and fleas?
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What are some of the environmental challenges a pathogen must overcome to successfully transmit through different routes?
What are some of the environmental challenges a pathogen must overcome to successfully transmit through different routes?
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What is the primary function of adhesion in pathogens?
What is the primary function of adhesion in pathogens?
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What is the definition of pathogenicity?
What is the definition of pathogenicity?
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Which of the following are examples of adhesion factors used by pathogens?
Which of the following are examples of adhesion factors used by pathogens?
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Which of the following best describes virulence factors?
Which of the following best describes virulence factors?
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What is the primary role of fimbriae/pili in bacterial adhesion?
What is the primary role of fimbriae/pili in bacterial adhesion?
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What is the role of membrane-associated virulence factors?
What is the role of membrane-associated virulence factors?
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Aside from motility, what other function can flagella sometimes serve?
Aside from motility, what other function can flagella sometimes serve?
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What are Type IV Pili primarily used for?
What are Type IV Pili primarily used for?
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What is the primary function of secretory virulence factors?
What is the primary function of secretory virulence factors?
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What is a reservoir in the context of disease transmission?
What is a reservoir in the context of disease transmission?
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What role do exopolysaccharides (EPS) play in bacterial adhesion?
What role do exopolysaccharides (EPS) play in bacterial adhesion?
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What distinguishes a human reservoir from an animal reservoir?
What distinguishes a human reservoir from an animal reservoir?
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Which of the following steps in bacterial infection involves breaking through host barriers?
Which of the following steps in bacterial infection involves breaking through host barriers?
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What is infectivity in the context of bacterial pathogenesis?
What is infectivity in the context of bacterial pathogenesis?
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What is the function of the "Toxin Complex" in bacterial pathogens?
What is the function of the "Toxin Complex" in bacterial pathogens?
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What is TSST-1?
What is TSST-1?
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Which of the following are examples of molecules produced by multi-enzyme 'factories' in bacteria?
Which of the following are examples of molecules produced by multi-enzyme 'factories' in bacteria?
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What is the role of non-ribosomal peptide synthases (NRPS)?
What is the role of non-ribosomal peptide synthases (NRPS)?
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What is the significance of specialized toxin delivery systems in bacterial pathogens?
What is the significance of specialized toxin delivery systems in bacterial pathogens?
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Which organisms are known to utilize the 'Toxin Complex' delivery system?
Which organisms are known to utilize the 'Toxin Complex' delivery system?
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How do some bacteria deliver virulence factors directly into host cells?
How do some bacteria deliver virulence factors directly into host cells?
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What is the primary function of exopolysaccharides (EPSs) produced by bacteria?
What is the primary function of exopolysaccharides (EPSs) produced by bacteria?
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How do bacterial capsules contribute to pathogenicity?
How do bacterial capsules contribute to pathogenicity?
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What is a key characteristic of biofilms that contributes to bacterial survival?
What is a key characteristic of biofilms that contributes to bacterial survival?
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How does the scavenging of serine by pathogens contribute to their survival?
How does the scavenging of serine by pathogens contribute to their survival?
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What is the primary effect of LPS (endotoxin) on the host?
What is the primary effect of LPS (endotoxin) on the host?
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What is the mechanism of action of superantigens?
What is the mechanism of action of superantigens?
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Which of the following is NOT a typical component of a biofilm?
Which of the following is NOT a typical component of a biofilm?
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What is dental plaque an example of?
What is dental plaque an example of?
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Flashcards
Pathogen
Pathogen
An organism that causes disease to its host.
Pathogenicity
Pathogenicity
The capacity to initiate an infectious disease.
Virulence
Virulence
The capacity to cause disease and its severity.
Transmissibility
Transmissibility
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Virulence factors
Virulence factors
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Steps to infection
Steps to infection
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Human reservoirs
Human reservoirs
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Animal reservoirs
Animal reservoirs
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Invertebrate vector
Invertebrate vector
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Pathogen adaptability
Pathogen adaptability
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Adhesion
Adhesion
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Attachment proteins
Attachment proteins
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Fimbriae
Fimbriae
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Flagella
Flagella
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Type IV pili
Type IV pili
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Exopolysaccharides (EPS)
Exopolysaccharides (EPS)
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Zoonosis
Zoonosis
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Environmental Reservoirs
Environmental Reservoirs
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Vibrio Cholera
Vibrio Cholera
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Direct Contact Transmission
Direct Contact Transmission
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Indirect Contact Transmission
Indirect Contact Transmission
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Droplet Transmission
Droplet Transmission
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Zoonotic Diseases from Animal Bites
Zoonotic Diseases from Animal Bites
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Contaminated Animal Products
Contaminated Animal Products
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Capsule
Capsule
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Biofilm
Biofilm
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Toxins
Toxins
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Endotoxin (LPS)
Endotoxin (LPS)
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Superantigens
Superantigens
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Cytokine storm
Cytokine storm
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Active combat mechanisms
Active combat mechanisms
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Toxic Shock Syndrome Toxin-1
Toxic Shock Syndrome Toxin-1
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Multi-protein injection machine
Multi-protein injection machine
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Toxin Complex
Toxin Complex
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Polyketide synthesis
Polyketide synthesis
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Gram-positive bacteria
Gram-positive bacteria
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Gram-negative bacteria
Gram-negative bacteria
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Specialized toxin delivery systems
Specialized toxin delivery systems
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Study Notes
Mechanisms of Bacterial Virulence
- Bacterial pathogens cause disease
- Pathogenicity is the ability to initiate disease
- Virulence is the severity of disease. Measures virulence using LD50
- Transmissibility is the ability to spread from one host to another
- Survival is the ability to withstand host immunity and reproduce
- Infectivity is the ability to breach host defenses
- Virulence factors are essential proteins or molecules for pathogenicity
Virulence Factors
- Cytosolic factors involve metabolic, physiological, and morphological changes
- Membrane-associated factors aid adhesion to host tissues/cells and evade host immunity
- Secretory factors invade tissues and evade innate and adaptive immunity
Steps to Infection
- Transmission: Exposure to pathogens
- Adherence: Binding to skin/mucosa
- Invasion: Breaking through barriers
- Survival: Growth at original and distal sites, production of virulence factors
- Tissue Damage: Toxicity and disease
Transmission: Reservoirs
- Human: Person-to-person transmission, asymptomatic carriage (e.g., COVID, HIV)
- Animal: Animal-to-animal, with humans as incidental hosts (e.g., Brucellosis, Anthrax, Plague)
- Environmental: Plants, soil, and water (e.g., Cholera, Legionnaires disease)
Transmission: Mechanisms
- Direct Contact: Physical transfer between infected individuals (e.g., skin-to-skin, sexual)
- Indirect Contact: Contact with a contaminated object (fomites) (e.g., Cholera, Salmonellosis)
- Droplets: Transmission via airborne droplets produced by coughing, sneezing (e.g., Influenza, Pneumonia)
- Zoonoses: Transmission from animals to humans (e.g., Animal bites, food products, animal hide products, invertebrate vector-borne)
Portals of Entry and Exit
- Portals of entry include mucous membranes, skin damage, placenta/birth transmission, specialised entry, and vector transmission.
- Portals of exit include respiratory tract, gastrointestinal tract, genitourinary tract, skin, and blood.
Factors Affecting Pathogen Transmission
- Environmental conditions: temperature, pH, oxygen levels, salt levels, host immune responses, nutrient availability
How Pathogens Achieve Infection
- Cell Surface Components: Adhesion, entry and structural defence against immunity
- Active Combat: Invasive enzymes, nutrient acquisition, toxins
- General Strategies: Dealing with phagocytosis, communication, subverting apoptosis
Adhesion
- The process of organisms attaching to tissues or cells
- Necessary for successful colonization
- Adhesion factors:
- Attachment proteins (pili, fimbriae, flagella)
- Specialized surface structures (EPS, CPS)
Adhesion Structures
- Initial attachment often mediated by protein appendages:
- Fimbriae/pili: Short fibers for sticking to host cells
- Flagella: For movement
Surface Structure (EPS)
- Exopolysaccharides (EPS): Consist of monosaccharide polymers secreted by bacteria into their environments
- Function: Hydrophobic, displace water, promoting closer contact, protective shield (capsule), prevent phagocytosis
Biofilms
- Formed by bacteria after initial attachment to enhance survival
- Locations: Inside host tissues, on abiotic surfaces (dental plaque, intestines)
- Structure: Contain biological polymers (exocellular polysaccharides, DNA, proteins)
- Function: Barrier against harmful factors, antibiotics and immune factors cannot penetrate.
Active Combat: Invasive Enzymes
- Coagulase: Coagulates fibrinogen, facilitates bacterial entry
- Kinases: Digest fibrin clots, breakdown host clots
- Hyaluronidase: Digests intercellular hyaluronic acid, spreading bacteria through tissues
- Collagenase: Hydrolyses collagen tissue, allowing bacteria greater freedom
- IgA protease: Destroy IgA antibodies, combating the host's immune system.
Active Combat: Toxins
- Toxin: Substance contributing to pathogenicity
- Toxigenicity: Ability to produce toxin
- Toxemia: Presence of toxin in the host's blood
- Toxoid: Inactivated toxin used in a vaccine
- Antitoxin: Antibodies against a specific toxin
- Examples are botulinum, shiga toxins, staphylococcal.
- Toxins vary in effect and potency and can be quite specific
Active Combat: LPS
- Gram-negative bacteria outer membrane component
- Triggers TLR4, causing inflammatory responses and fever
- Little innate toxicity itself
Active Combat: Exotoxins
- Specifically synthesized and released in response to host signals
- Types:
- Single polypeptide toxins
- Multiple polypeptide toxin complexes
- Small "drug-like" molecules
- Toxins directly "injected" by specialist secretion systems
Active Combat: Single Chain Toxins
- Example: S. aureus α-toxin creates pores in host cell membranes
- Many toxins disrupt phospholipid bilayers
Active Combat: Superantigens
- Directly target immune system
- Trigger non-specific T-cell activation, cytokine storm
- Bridge between class II MHC and TCR
Active Combat: Multiple Subunit Protein Toxins
- Multi-protein injection machines delivering toxic payloads across host cell membranes
Active Combat: Non-protein Small Drug-like Toxins
- Other toxins are evolved specifically to damage or manipulate the host
- Some examples include toxins, immune inhibitors, antibiotics, siderophores
Multi-enzyme "Factories"
- Secondary metabolite genes like NRPS act as factories to produce molecules
- Molecules include toxins, immune inhibitors, antibiotics, siderophores
Active Combat: Specialized Toxin Delivery Systems
- Secretion systems for toxin release into host cells
- Types:
- Type I, Type II, Type III, Type IV, Type V, Type VI, Type VII
- Occur in both Gram-positive and Gram-negative bacteria
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Description
Test your knowledge on disease transmission methods and zoonotic diseases with this quiz. It covers various topics including historical outbreaks, modes of transmission, and infection sources. Challenge yourself to identify key concepts in the field of epidemiology.