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Questions and Answers
What defines a primary pathogen?
What defines a primary pathogen?
Which term describes the ability of a pathogen to cause disease?
Which term describes the ability of a pathogen to cause disease?
What role do virulence factors play in the infection process?
What role do virulence factors play in the infection process?
What is the significance of the chain of infection in understanding virulence?
What is the significance of the chain of infection in understanding virulence?
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What defines opportunistic pathogens?
What defines opportunistic pathogens?
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What environment do pathogens require to survive and thrive?
What environment do pathogens require to survive and thrive?
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How is virulence measured?
How is virulence measured?
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Why is it important to understand the aetiology of oral diseases?
Why is it important to understand the aetiology of oral diseases?
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Which of the following is a key function of virulence factors in pathogens?
Which of the following is a key function of virulence factors in pathogens?
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What type of resources provides information on virulence factors of bacterial and viral pathogens?
What type of resources provides information on virulence factors of bacterial and viral pathogens?
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The ability to resist physical removal is considered which characteristic of pathogens?
The ability to resist physical removal is considered which characteristic of pathogens?
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Which of the following URLs leads to information about bacterial pathogenesis?
Which of the following URLs leads to information about bacterial pathogenesis?
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Which of the following aspects is NOT typically associated with virulence factors?
Which of the following aspects is NOT typically associated with virulence factors?
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What type of adhesion does Enterotoxigenic E. coli (ETEC) utilize for attachment?
What type of adhesion does Enterotoxigenic E. coli (ETEC) utilize for attachment?
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What function do capsules produced by some bacteria primarily serve?
What function do capsules produced by some bacteria primarily serve?
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Which of the following pathogens is associated with the disease cholera?
Which of the following pathogens is associated with the disease cholera?
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What is the role of exoenzymes in the context of pathogenic invasion?
What is the role of exoenzymes in the context of pathogenic invasion?
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What is the adhesion mechanism used by Streptococcus mutans in causing dental caries?
What is the adhesion mechanism used by Streptococcus mutans in causing dental caries?
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Which statement accurately describes endotoxins?
Which statement accurately describes endotoxins?
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Which component found in the cell wall of Mycobacterium tuberculosis contributes to its virulence?
Which component found in the cell wall of Mycobacterium tuberculosis contributes to its virulence?
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What characterizes exotoxins compared to endotoxins?
What characterizes exotoxins compared to endotoxins?
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What disease is primarily caused by Neisseria gonorrhoeae?
What disease is primarily caused by Neisseria gonorrhoeae?
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What is the consequence of high concentrations of endotoxins in the blood?
What is the consequence of high concentrations of endotoxins in the blood?
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What happens to exotoxins at temperatures above 41°C (106°F)?
What happens to exotoxins at temperatures above 41°C (106°F)?
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What property does the capsule of a bacterium possess that deters phagocytosis?
What property does the capsule of a bacterium possess that deters phagocytosis?
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Which bacterial adhesin is associated with respiratory epithelial cells?
Which bacterial adhesin is associated with respiratory epithelial cells?
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Which type of pathogens are primarily responsible for producing exotoxins?
Which type of pathogens are primarily responsible for producing exotoxins?
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What is a common role of fimbriae in some pathogenic bacteria?
What is a common role of fimbriae in some pathogenic bacteria?
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What is toxigenicity in the context of pathogens?
What is toxigenicity in the context of pathogens?
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Which statement correctly describes the protective coat of certain pathogens?
Which statement correctly describes the protective coat of certain pathogens?
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Which of the following bacteria is directly linked to traveller's diarrhoea?
Which of the following bacteria is directly linked to traveller's diarrhoea?
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Which of the following types of toxins can be lethal in low concentrations?
Which of the following types of toxins can be lethal in low concentrations?
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What term describes the presence of bacteria in the bloodstream?
What term describes the presence of bacteria in the bloodstream?
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What term describes the presence of bacteria in the bloodstream?
What term describes the presence of bacteria in the bloodstream?
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Which virulence factor aids Staphylococcus aureus in avoiding phagocytosis?
Which virulence factor aids Staphylococcus aureus in avoiding phagocytosis?
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What type of antigenic variation involves gene re-assortment resulting in major changes in viral proteins?
What type of antigenic variation involves gene re-assortment resulting in major changes in viral proteins?
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What is the function of gingipains produced by Porphyromonas gingivalis?
What is the function of gingipains produced by Porphyromonas gingivalis?
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Which of the following is a characteristic of Streptococcus mutans as a virulence factor?
Which of the following is a characteristic of Streptococcus mutans as a virulence factor?
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Which immune evasion strategy involves the breakdown of T lymphocytes?
Which immune evasion strategy involves the breakdown of T lymphocytes?
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What is the role of adhesins in viral pathogens?
What is the role of adhesins in viral pathogens?
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Which term describes the presence of toxins in the blood?
Which term describes the presence of toxins in the blood?
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Which factor does NOT contribute to the virulence of Streptococcus mutans?
Which factor does NOT contribute to the virulence of Streptococcus mutans?
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What process allows pathogens to modify surface proteins to avoid detection by the immune system?
What process allows pathogens to modify surface proteins to avoid detection by the immune system?
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What strategy do successful pathogens utilize to ensure their survival and transmission?
What strategy do successful pathogens utilize to ensure their survival and transmission?
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What is one method by which pathogens adapt to evade the immune defenses of their hosts?
What is one method by which pathogens adapt to evade the immune defenses of their hosts?
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Why is it advantageous for a pathogen to avoid immediate death of the host?
Why is it advantageous for a pathogen to avoid immediate death of the host?
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Which adaptation might a pathogen employ to survive inside a host's cells?
Which adaptation might a pathogen employ to survive inside a host's cells?
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What is a potential consequence of a pathogen's ability to change antigens frequently?
What is a potential consequence of a pathogen's ability to change antigens frequently?
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Study Notes
Terminology
- Pathogen: A microorganism capable of causing disease in a host organism
- Primary pathogen: A microbe from the environment that can cause disease in a healthy individual
- Opportunistic pathogen: A member of the normal microbiota that causes disease only in immunocompromised individuals
- Pathogenicity: The ability of a pathogen to cause disease
- Virulence: The degree or intensity of pathogenicity
- Virulence factors: Mechanisms that determine the extent to which a pathogen causes damage, invasion, and infectivity
Process of Infection
- To survive, pathogens require:
- A suitable environment
- A source of nutrients
- Protection from harmful elements
Bacterial Adhesins
- Adhesins: Virulence factors enabling pathogens to attach to host cells
-
Specific Examples:
- Streptococcus pyogenes (Strep throat): Protein F adheres to respiratory epithelial cells
- Streptococcus mutans (Dental caries): Adhesin P1 attaches to teeth
- Neisseria gonorrhoeae (Gonorrhoea): Type IV pili bind to urethral epithelial cells
- Enterotoxigenic E. coli (ETEC) (Traveller's diarrhoea): Type 1 fimbriae attach to intestinal epithelial cells
- Vibrio cholerae (Cholera): N-methylphenylalanine pili bind to intestinal epithelial cells
Capsules
- Some bacteria produce capsules that:
- Aid in adhesion
- Evasion of the immune system (preventing phagocytosis)
- Capsule composition prevents antibody adhesion
- Capsule size deters phagocytosis
Fimbriae and Cell Walls
- Fimbriae on some Streptococcus species contain M protein, altering the bacterial surface and hindering phagocytosis
- Mycolic acid, a waxy substance in the cell wall of Mycobacterium tuberculosis, acts as a protective coat deterring killing mechanisms during phagocytosis
Exoenzymes
- Extracellular enzymes secreted by cells that function outside of those cells
- Enable invasion of host cells and deeper tissues
- Breakdown specific tissue structures, supporting pathogen growth and defending against the immune system
Exoenzyme Examples
- Collagenases: Break down collagen, a major component of connective tissue
- Hyaluronidases: Break down hyaluronic acid, a component of extracellular matrix
- Proteases: Break down proteins, facilitating tissue invasion
- Coagulase: Catalyzes the conversion of fibrinogen to fibrin, forming a clot that protects the bacteria from the immune system
- Kinases: Dissolve fibrin clots, allowing bacteria to escape and spread
- DNases: Break down DNA, reducing the viscosity of mucus and facilitating bacterial spread
Toxins
- Biological poisons produced by pathogens that invade and damage tissues
- Toxigenicity: The ability of a pathogen to produce toxins to cause damage to host cells
-
Types of Toxins:
- Endotoxins: Lipopolysaccharide components of the outer membrane of gram-negative bacteria; stimulate a general systemic inflammatory response; stable at high temperatures; can cause severe inflammatory reactions and even death in high concentrations
- Exotoxins: Potent protein molecules produced by a variety of bacteria (mainly gram-positive); highly specific in their action and target cells; inactivated by heat; low concentrations can be lethal; categorized into three groups based on their mode of action: intracellular targeting, membrane disrupting, superantigens
Terminology for Pathogens in the Bloodstream
- Bacteraemia: Presence of bacteria in the blood
- Pyaemia: Presence of pus-forming bacteria in the blood
- Toxaemia: Presence of toxins in the blood
- Septicaemia: Multiplying bacteria in the blood
Virulence Factors Promoting Infection
- Coagulase: Produced by Staphylococcus aureus, triggers fibrinogen conversion to fibrin, coating bacteria in clots and preventing phagocytosis
- Kinases: Digest fibrin clots, allowing bacteria to escape and spread
- Antigenic Variation: Surface proteins change to avoid recognition by the host's immune system, e.g., some viruses like influenza and HIV
- Leukocidins: Destroy phagocytes
- T Cell Destruction: Kill T lymphocytes
- Intracellular Position: Pathogens reside inside host cells, evading immune defenses
Viral Virulence
-
Adhesins: Mediated by adhesions present in the viral capsid or membrane envelope; interact with specific cell receptors (tropism)
- Example: Spike protein hemagglutinin on influenza virus; glycoprotein g20 on HIV
-
Antigenic Variation:
- Antigenic Drift: Minor changes in spike proteins due to point mutations
- Antigenic Shift: Major changes in spike proteins resulting from gene re-assortment (major outbreaks)
Virulence Factors in Oral Health
-
Porphyromonas Gingivalis: A primary pathogen in periodontal disease
- Fimbriae: Modify and stimulate immune responses (cytokine secretion or inhibition)
- Gingipains (proteases): Break down periodontal structural proteins like collagen, elastin & fibronectin
-
Streptococcus Mutans: A major contributor to dental caries
- Adhesion, acidogenicity, acid tolerance: These factors work together to alter the ecology of dental plaque, favoring the development of caries
Pathogen-Host Interactions
- Pathogens must evade immune defenses to survive and reproduce.
- Pathogens use strategies like antigenic variation to change their surface antigens, making it difficult for the immune system to recognize and attack them.
- Some pathogens can survive inside host cells, hiding from the immune system.
Successful Pathogens
- Successful pathogens exploit host resources while minimizing harm to the host.
- This allows the pathogen to survive long enough to reproduce and spread to new hosts.
- Pathogens that kill their host too quickly are less likely to be transmitted.
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Description
Test your knowledge on the terminology and processes related to pathogens and infection. This quiz covers primary pathogens, opportunistic pathogens, and virulence factors, providing a comprehensive understanding of how infections occur.
