Principles of Infection III Flashcards
What are the 4 main stages of infection?
Transmission
Infection
Pathogenicity
Virulence
What is the transmission stage of infection?
The host has to acquire the organism.
What is the infection stage of infection?
The organism has to reproduce inside the host.
What is the pathogenicity stage of infection?
Interacting the host in a way that causes disease.
What is the virulence stage of infection?
This is the severity of the disease stage.
What are the main virulence factors?
Adhere to and invade host tissues.
Evade host defences.
Proliferate in the host.
Cause damage = produce toxins // host - pathogens interactions.
What does virulence factors allow to take place?
Enables the host to replicate and spread within a host.
How is it possible to ‘evade host defences’?
Achieved by entering the bloodstream.
What is the name given for the production of toxins?
Toxigenicity.
What is the effect of the production of toxins?
This can cause tissue damage = which leads to LOW BLOOD PRESSURE.
How does virulence factors arise?
These factors are often encoded and translated for genes in chromosomal DNA.
What are pili adhesions ?
This is when the pili attaches a bacterial cell to a SPECIFIC surface // other cells.
This can aid in attachment between the bacterial cells.
What process is pili adhesions attached to?
Adherence.
What are the two types of invasions?
Intracellular.
Extracellular.
What is intracellular invasion?
This when the microbe actually penetrates the cells of a HOST TISSUE and SURVIVES.
What is extracellular invasion?
This is when a microbe breaks down the barriers of a tissue to spread in the host while remaining OUTSIDE of the host cells.
Which enzymes aid extracellular invasion?
Staphylokinase
Hyaluronidase
Streptokinase
What are the 3 main evade host defences for bacteria?
Capsule
Cell Wall
Toxins
Explain more about the capsule host defence.
Protects the bacteria from phagocytosis.
DOES NOT allow opsonising antibodies to be recognised by phagocytic host defence cells.
What are the host defence cells?
Macrophages
Neutrophils
Explain more about the cell wall host defence.
These contain endotoxins and thus, activate a pathway of events which WEAKEN THE HOST.
The host deteriorates.
What is the weakening of the host known as?
Septic Shock.
Explain more about the toxins host defence.
These molecules are secreted by bacteria to destroy and damage host tissues.
What are the 2 main evade host defences for viruses?
Antigenic Drift
Antigenic Shift
Explain more about the Antigenic Drift.
BRINGS ABOUT MINOR CHANGE.
This is the accumulation of mutations within the genes which codes for antibody - binding sites.
Explain more about the Antigenic Shift.
BRINGS ABOUT MAJOR CHANGE.
2 / more different strains of viruses combine.
Forms a new subtype = This has a mixture of surface antigens of the 2 / more ORIGINAL strains.
What is the horizontal gene transfer?
This enables bacteria to respond and adapt to their environment RAPIDLY by acquiring large DNA sequences from another bacterium in a single transfer.
How are virulence factors determined?
These factors are genetically determined.
What is the donor bacterium?
This carries the DNA sequence called the ‘ Fertility Factor.’
What is a pilus?
This is a thin tube - like structure which is used as a cell adhesion mechanism.
What is the ‘F - Factor’?
Donor produces a PILUS.
They contact the recipient and thus, the donor bacterium transfers the genetic material to recipient bacterium.
