Introduction to Infection and Immunity Flashcards
What are the three domains of the phylogenetic tree of life?
Bacteria
Archaea
Eukaryota
What are the Parasites?
Helmiths Lice Mites Protists Fungi
What are the microorganisms?
Protists
Fungi
Bacteria
What are the non-cellular agents?
Viruses
Prions
What do transmissible organisms move between species?
Ebola HIV BSE/nvCJD- cattle Leprosy- between animals Tuberculosis Ascaris Measles- dogs Influenza- birds Schistosomes Malaria Leishmaniasis Plague- rats
What is mutualism?
Both members benefit
What is commensalism?
One benefits
What is parasitism?
One harms the other
What is pathogenicity?
The ability to cause disease
What is virulence?
The measure of pathogenicity
How do transmissible diseases cause disease?
Pass between hosts Attach to and enter host Survive the host's antimicrobial defences Disperse within the host Cause disease
What are the chain of events in an infectious disease?
Transmission Entry Attachment and colonisation Multiplication in vivo Evasion of host defence mechanisms Damage to the host
What is transmission?
Whether or not disease occurs depends on many factors: Pathogenic potential of infectious agent Susceptibility of host Way in which they encounter Species Genetics (selection of ancestors) Age Gender Nutritional status Immune status
What is entry of an infectious disease?
Through local or systemic effects
Mucosal surfaces
Skin
How does infectious disease infect through mucosal surfaces?
Respiratory tract- Myobacterium tuberculosis, influenza virus
Gastrointestinal tract- salmonella typhi, poliovirus
Genitourinary tract- Neisseria gonorrhoeae, HIV
How does infectious disease infect through skin?
Insect & tick bites- malaria, filariasis, typhus
Animal bites- rabies
Wound contamination- tetanus
Direct invasion- hookworms, schistosomes, myiasis
Contact- smallpox, measles, scabies
In what ways does attachment and colonisation occur?
Competition with normal flora
Specific adhesion mechanisms to host receptors
Evade and survive barriers
Localised infection- establishment phase, followed by dissemination
Generalised/systemic infection or toxin spread from a localised site
How does infection occur by multiplication in vivo?
The organism must find appropriate environmental conditions e.g. Nutrients pH Temperature Aerobic/ anaerobic
What are the steps of evasion of host defence mechanisms?
Innate (non-specific)
Adaptive (specific) immune mechanisms
Evasion necessary until preferred site of infection is reached or for long enough to complete the cycle in the host and to ensure spread to fresh hosts
Manipulation of host immunity
In what ways can damage to the host occur?
Direct damage by infectious agent
Indirect damage via inflammation
Indirect damage via immune response
What ways can direct damage happen?
Multiplication within and destruction of host cells
Exotoxins
How does multiplication within and destruction of host cells cause direct damage?
Viruses- poliovirus/neurones
Some bacteria- mycobacterium tuberculosis/macrophages
Some protists- plasmodium/erythrocytes
How do exotoxins cause direct damage by infectious agent?
Promoting survival or spread- hyaluronidase S. aureus
Damaging or destroying cells- leucocidin S. aureus
Interfereing with cell metabolism- diphtheria toxin
Affecting passage of nerve impulses- tetanus toxin
In what ways can indirect damage via inflammation cause damage to the host?
Inflammatory response is an important part of host defences
Over activity can damage the host’s own tissues
Inflammatory mediators:
1.From cells damaged by infection
2.From some pathogens
3.From cells of the innate immune system
In what ways can indirect damage via immune response cause damage to the host?
Immune response is a vital part of host defences- over activity (hypersensitivity) can cause tissue damage (immunopathology)
What are the confounding factors in controlling and eliminating transmissible diseases?
Drug and vaccine development- feasibility, time, cost
Human behaviour
Social disruption and warfare
‘Alternative’ and ‘traditional’ medicine
Pathogen ingress to human population from other species
Pathogen evolution
Climate and environmental change
Politics, sociology, religious and cultural beliefs, false information
Why can pathogens continue to circumvent our immune system?
They evolve and adapt to our drugs and vaccines
What are some examples of pathogens who have evolved to continue to harm?
Myxoma virus
Syphillis
Influenza virus
