BIOLOGY 2EE3 Lecture Notes - Lecture 12: Magnaporthe Grisea, West Nile Fever, Microorganism

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Infectious Diseases and Bacterial Pathogenesis
Disease – disturbance in normal functioning of an organism
oInfectious: caused by a microbe, can be transmitted from host to host. Examples: Influenza, HIV,
hepatitis B
oZoonotic – infectious disease of animals that can cause disease when transmitted to humans. Examples:
Rabies, West Nile fever
Pathogens – microbes frequently associated with disease production
oPathogenesis – mechanism a microbe uses to cause the state of disease
oInfection – replication of pathogen on or in host cell
oNot all have the same ability to cause the disease
-Primary – produce disease readily in healthy hosts
-Opportunistic – cause disease when displaced to an unusual site or when host has a weakened
immune system
Case-to-infection ratio – proportion of infected individuals to whom that develop the disease
Virulence – measure of disease severity
oPathogens can weaken over time or show different virulence levels due to genetic differences
oAttenuated (weakened, less virulent) strains show decreased virulence = effective vaccines
oAvirulent strains = no longer cause disease
Microbial Virulence
Strategies
Gain entry to the host
Attach and invade specific cells or tissues
Evade host defences
Obtain nutrients from host
Exit the host
Note – all these steps eventually cause damage to cell
Attachment, invasion and replication
Attachment may occur through
oProtein interactions – viruses more often use a specific host cell receptor
oGeneralized interations – rice blast fungus spores often adhere to most hydrophobic surfaces, including
cells
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Document Summary

Disease disturbance in normal functioning of an organism: infectious: caused by a microbe, can be transmitted from host to host. Examples: influenza, hiv, hepatitis b: zoonotic infectious disease of animals that can cause disease when transmitted to humans. Primary produce disease readily in healthy hosts. Opportunistic cause disease when displaced to an unusual site or when host has a weakened immune system. Case-to-infection ratio proportion of infected individuals to whom that develop the disease. Attach and invade specific cells or tissues. Note all these steps eventually cause damage to cell.

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