32 Questions
What is a characteristic of a commensal microorganism?
Lives in/on a living host without causing disease
What is a microorganism considered as when it is able to cause disease?
Pathogenic
What is the term for a healthy individual who possesses a microorganism and transmits it?
Carrier
Why are carriers considered serious?
Because they can communicate normally with the public and carry the organism
What is a factor that can cause a commensal microorganism to become opportunistic?
All of the above
What is the definition of infection?
Relation between microorganism and host
What is the term for the destruction of host tissue by the organism due to invasion of tissue, toxin production, and other virulence factors?
Disease
What type of carrier has the microorganism in their body for a short period of time?
Transient carrier
What is the genetically determined degree of pathogenicity in microorganisms?
Virulence
Which of the following is NOT a type of adherence factor in bacteria?
Capsule
What is the function of M protein in Streptococci?
To inhibit phagocytosis
Which of the following bacteria has fimbriae as an adherence factor?
All of the above
What is the term for the ability of microorganisms to cause disease?
Pathogenicity
Which of the following is an example of an invasive factor?
Lecithenase
What is the term for the ability of microorganisms to resist phagocytosis?
Antiphagocytic activity
Which of the following is a type of invasive factor that helps bacteria to survive intracellularly?
Capsule
What is the nature of exotoxins?
Protein
Which of the following is an example of a cytolysin?
Cl. perfringens
What is the mechanism of action of A-B component toxins?
The B part binds to a specific receptor, facilitating the entry of the A part
Which of the following bacteria can escape phagosome-lysosome fusion?
Lesteria
What is the site of action of endotoxins?
General effect
What is the control of production of exotoxins?
Genes on plasmids and bacteriophage
What is the action of superantigens?
Activate a large number of T-cells, leading to a massive immune response
Which of the following is an example of a superantigen?
Staphylococcal TSST
Which of the following is a mechanism of action of endotoxins?
Complement C3a, C5a
What is the composition of endotoxins?
Lipopolysaccharides
Which of the following is a characteristic of exotoxins?
Diffusible
What is the difference between an infectious agent and a pathogen?
A pathogen is a type of infectious agent that causes disease
What is the role of Hageman factor in endotoxin-mediated disease?
To cause Disseminated Intravascular Coagulation (DIC)
What is a commensal?
An organism that lives on or in another organism without causing harm
Which of the following is a step in the chain of infection?
Pathogen transmission
What is a bacterial carrier?
An individual who is colonized with bacteria but shows no symptoms
Study Notes
Pathogens and Microorganisms
- A pathogen is a microorganism that can cause disease.
- Types of microorganisms:
- Saprophytic: live freely in nature.
- Parasitic: live in/on a living host.
- Pathogenic: cause disease.
- Commensal: live in/on a living host without causing disease.
- Opportunistic: commensals that can cause disease under certain conditions.
Bacterial Carrier
- A carrier is a healthy individual who possesses microorganisms and can transmit them.
- Types of carriers:
- Transient: possess microorganisms for a short period (incubation period).
- Permanent: possess microorganisms for a long period (chronic).
- Carriers are serious because they can communicate normally and carry the organism throughout the entire epidemic period.
Infection and Disease
- Infection: the relationship between a microorganism and a host.
- Disease: the destruction of host tissue by microorganisms due to:
- Invasion of tissue.
- Toxin production.
- Other virulence factors.
Factors that Govern Disease Production
- Microbial factors:
- Virulence: the degree of pathogenicity, determined by genes.
- Pathogenicity: the ability to cause disease.
- Host resistance factors:
- Natural immunity.
- Acquired immunity.
Virulence Factors of Bacteria
- Invasive factors:
- Adherence factors (pili, fimbriae, glycocalyx).
- Ability to invade tissues, multiply, and spread rapidly.
- Toxin production:
- Exotoxins: protein toxins produced by living bacteria, acting on specific cells.
- Endotoxins: lipopolysaccharide toxins produced by dead bacteria, causing a general effect.
Exotoxins and Endotoxins
- Exotoxins:
- Produced by living bacteria.
- Act on specific cells.
- Can be controlled by genes on plasmids and bacteriophage.
- Examples: diphtheria toxin, cholera toxin, tetanus toxin.
- Endotoxins:
- Produced by dead bacteria.
- Cause a general effect (endotoxic or septic shock).
- Can be controlled by genes on chromosomes.
- Examples: Gram-negative bacteria.
Properties of Exotoxins and Endotoxins
- Exotoxins:
- Location of genes: plasmid, bacteriophage, PAIs.
- Composition: proteins.
- Action: specific.
- Heat stability: labile, destroyed at 60°C.
- Diffusibility: diffusible.
- Immunogenicity: strong.
- Toxicity: strong.
- Convertibility to toxoid: yes.
- Endotoxins:
- Location of genes: bacterial chromosome.
- Composition: lipopolysaccharide.
- Action: non-specific.
- Heat stability: stable at 100°C for 1 hour.
- Diffusibility: not diffusible.
- Immunogenicity: weak.
- Toxicity: weak.
- Convertibility to toxoid: no.
This quiz covers the basics of microbiology, including types of pathogens, bacterial carriers, infection, and disease. It also explores factors that contribute to disease production and bacterial pathogenicity.
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