MFD.10 Flashcards
How do bacteria cause disease:
1) Pathogen
2) Opportunistic pathogen
3) Infection
• PATHOGEN: An organism that causes disease in otherwise healthy individuals
• OPPORTUNISTIC PATHOGEN: An organism which requires the host to have a pre-¬‐existing defect in its defences before it can cause disease
• INFECTION: Growth of a non-¬‐native microorganisms at a body site, with or without damage to the host
•
How do bacteria cause disease:
1) virulence
2) virulence factors
VIRULENCE: a measure of the capacity of an organism to cause disease
• VIRULENCE FACTORS: properties of a bacterium which contribute to its virulence
What are the 2 types of infection?
1) Endogenous
2) Exogenous
Define Endogenous infections:
are caused by an infectious agent that is already present in the body, but has previously been inapparent or dormant
Define endogenous infections:
are caused by an infectious agent that is already present in the body, but has previously been inapparent or dormant
Define Exogenous infections:
are acquired from sources outside the patient
Pathogens possess a range of virulence factors. Name them:
– Adhesins
– Invasins (enter cells )
– Toxins
– Extracellular enzymes
What are the stages of infection?
1) Exposure
2) Adherence
3) Invasion
4) Infection
5) THEN..
Toxicity: toxin effects are local or systemic
OR
Invasiveness: Further growth at original and distant sites
6) Tissue Damage, disease
Adherence
Initial attachment involves interaction between surface structures of bacteria and host tissue. What structures are used to do this?
- Bacterial surface structures -¬‐ pili, fimbriae, surface proteins
- Host tissue receptors —glycoproteins, tissue— specific antigens (HLA etc.)
What are the innate ways the host defends itself from pathogens?
- Skin (keratinised, shedding of outer layers)
- Flushing (saliva, urine, peristalsis in gut)
- Secretions (lysozyme, stomach acid, bile salts)
- Mucous membranes (cilia)
- Normal bacterial population (colonisation resistance)
What are the adaptive ways the host defends itself from pathogens?
- Phagocytosis
- Inflammation, fever
- Antibodies
Explain how bacteria evade the following adaptive immune responses:
1) Phagocytosis
2) Inflammation/fever
3) Antibody
Phagocytosis: Capsules (prevent antibody attachment enabling phagocytosis)
Inflammation/fever: Heat shock response (lets them survive the higher temperature)
Antibody: Breakdown of immunoglobulins, kill host defence cells, intracellular
What are commensal flora?
friendly bacteria, provide us with benefits
How do bacteria evade normal bacterial population/ commensal bacteria?
Metabolic end products, bacteriocins, bacteriophage etc
What is bacteraemia
• Invasion into bloodstream
What is septicaemia.
• Infection in the bloodstream
What is the name given to the following definition:
• Invasion into bloodstream
bacteraemia
What is the name given to the following definition:
• Infection in the bloodstream
septicaemia.
Following attachment after invasion, what do the bacteria then do?
invade epithelial cells
Compare the terms infection and disease:
- Infection is a situation when a microorganism that is not a natural (commensal) coloniser grows within the host, whether or not it causes damage.
- Disease arises when there is damage to the host.
How can the bacteria spread once within the cells of a host?
- Through lungs, gut, urinary tract, blood
- via sinuses and body cavities
- Tracking along nerve pathways
- Direct cell-¬‐to-¬‐cell
- Tissue breakdown
Give the 2 types of toxins ( a microbial virulence factor):
1) endotoxin
2) exotoxin
Give the 3 types of tissue-degrading enzymes( a microbial virulence factor):
- collagenase
- hyaluronidase
- haemolysin
Give an example of an endotoxin found only in gram-negative bacteria:
LPS