Pathogens and Hosts Flashcards
Make a list of the signs and symptoms that someone has an infection./
inflammation
pain
pyrexia
tachycardia
rigors
increased white cell count
Increased C reactive protein (CRP)
What is a pathogen?
an organism which can cause disease
What is a commensal?
s an organism which is part of normal flora e.g. E. coli in the gut, Staph aureus in the nose, axilla
What can be an issue between pathogens and commensal?
The distinction between these is not always clear
What can be used to determine whether a microorganism causes a disease?
Koch’s Postulates
What does Koch’s Postulates state a microorganism should be able to do in order to cause a disease?
organism must be found in all cases of the disease
able to be cultured outside the body for several generations
should reproduce the disease on inoculation
What is pathogenicity?
The capacity of a micro-organism to cause an infection
What are the requirements of The capacity of pathogenicity?
Infectivity
Virulence
What does infectivity mean?
Ability to become established.
What does virulence mean?
Ability to cause harmful effects once established
Define Infectivity
Ability to become established on or within a host
How does E.coli demonstrate infectivity?
Receptor on uroepithelial cells
What is virulence conferred by?
Virulence factors.
List some virulence factors.
Invasiveness
Toxin production
Evasion of immune system
What is virulence specific to?
Strains not species
How are exotoxins released?
Extracellularly by the micro-organism
What are enterotoxins?
exotoxins which act on the GI tract
What is endotoxin structurally part of?
Gram negative cell wall
What are super antigens able to do?
Able to stimulate division of T cells in the absence of specific antigen
What does overwhelming cytokine production cuase?
Toxic shock
Give an example of an endotoxin
Lipopolysaccharide-
1. Lipid A
2.Oligosaccharide core
3.Specific polysaccharide chain
What reponses do endotoxins produce?
Cytokine production
Fever, rigors, hypotension, tachycardia, collapse
What are the three characteristics of virus pathogenic mechanisms?
Cell destruction following virus infection
Virus-induced changes to cellular gene expression
Immunopathogenic disease
Describe cell destruction following virus infection
Death of T4+ cells by HIV
Describe Virus-induced changes to cellular gene expression
Cellular transformation by tumour viruses.
Give two examples of Immunopathogenic disease
Influenza A virus.
Coxsackievirus-induced myocarditis.
Name some sites of viral entry.
Respiratory tract
Alimentary tract
Urinogenital tract
Conjunctiva
Arthropod
Skin
Capillary
Describe acute infection.
Virus increases and decreases.
Describe latent infection.
Virus increases and then decreases so is unnoticed but does not fully go away. Increases in the future.
Describe chronic infection.
Virus increases, may decrease slightly but then stays the same.
Describe tumour virus infection.
Slight increase in early disease but then decreases and stays constant before rapidly spiking in the future.
Separated into early and late disease.
Name two acute viruses.
Influenza A virus
Enterovirus
Discuss acute virus infection.
Localised to specific site of body
Development of viraemia with widespread infection of tissues.
Give an example of a latent virus infection.
Herpes simplex virus
Explain how a latent virus infection of herpes may come back.
Primary infection of epithelial cells.
Virus migration to the ganglia.
Virus remains latent in nucleus (No Virus Replication.)
Stimuli (e.g. sunlight) reactivates virus.
Virus migration to epithelial cells leading to virus replication.
Name two tumour virus infections.
Papillomaviruses (HPV)
Retroviruses
Don’t hate me but describe the process of retrovirus replication
I’M SORRY
After a retrovirus enters a host cell, reverse transcriptase converts the retroviral RNA genome into double-stranded DNA.
This viral DNA then migrates to the nucleus and becomes integrated into the host genome.
Viral genes are transcribed and translated.
New virus particles assemble, exit the cell, and can infect another cell.
How can retroviruses cause a tumour?
Virus infects cell.
Virus nucleic acid, as DNA, integrates into cellular genome.
Virus causes changes in cellular gene expression.
Uncontrolled cell multiplication and tumour formation.
