pathogeneisis ( topic 5 )

What is a pathogen

A microorganism that can cause disease limited to bacteria viruses fungi and Protozoa

What is pathology

The study of disease involves the malfunction or disruption of a biological process

What is a parasite

On or in host and adapted to host causing harm usualy larger multicellular organisms

What is virulence

The degree to which an anrganism can cause disease

What is a virulence determinant

A component that contributes to the virulence of an organism

Expalin whay was the criteria kock introduced to prove an infect is disease

Microorganism must be present in all disease cases

Microorganism must be isolated and town in pure culture

The disease is reproved when pure culture of microorganism is inoculated into a susceptible host

The microorganism is recovered from the experimentally infected host

What was the shortcomings of kock’s ostulates

• people can be asymptamatic carriers

• Not all pathogen a can be grown in the lab it very difficult to replicate exact medium and conditions it needs

• Appropriate host model may not be available and to use a primary host and inject them with an infection isnt ethical

• Diffrent levels of infection look diffrent in diffrent peopel even if its the same disease

What is a commensals

Bacteria derive benefits of niche without harming host

What are some strategies bacteria use to avoid non specific him

• protease and motility

• Chemotastic motility

• Antibacterial compounds

• Capsule and lps

• Siderophores and high affinity iron binding proteins

• Capsule and intracellular survival ( biofilm formation )

Mechanisms of pathogenesis

Exotoxin production - pathogen secretes toxin that damages or alters cell function

Endotoxin - release of endotoxin from gram negative I bacterial lps

Cell invasion - cell death due to pathogen interning cell and replicating

Immunopathological damage - immune response damages host tissue

What is molecular kock’s postulates

Phenotype or property under investigation should be related with a pathogenic strain of a species

Inactivation of the gene related to virulence factors should lead to a measurable decrease in pathogenicity

What are adhesins

Adhesion to host cell surface

Sticking to each other to form micro colony

Maturation repulsion of surfaces ( host top bacterium. )

Multistage - more intimate adhesion

Fimbrial adhesins - thin rod like structures

Describe the features of exotoxins 1

Cell surface active toxin

Binds to immune cells and results in massive overstimulation

Cytokines release

Immunopathological damage

Describe the features of exotoxins 2

They are membrane damaging toxins

Form pore in host cell membrane

Loss of barrier function

Influx ca2+ into cells

What are the features of exotoxins three

Intracellular toxins

Enter. Ells and has enzymatic activity

Delivery mechanisms

They directly inject type 2 exotoxins into the host cell membrane

What does the a and b subunits log the exotoxins do

A subunit - enters through membrane and has toxic function

B subunit - attaches to target region on the cell membrane to deliver subunit a

What is invasion

Bacteria can enter survive within and kill host cells

Avoid host defences

Nutrient rich environments

Induction of cell uptake

Enter vacuole and resist killing or exit vacuole

What are biofilms

Thinking about microorganism growing in solutions as simple entities

Complicated as a tissue

Epithelial surfaces t