molecular basis of parasite host-cell interactions Flashcards
1
Q
pathogenicity
A
- not all micro-organisms cause disease
- most are never pathogenic
- few can be, and few are always pathogenic
- very few can cause death
2
Q
process of infection
A
- growth/multiplication of microbe in host
- doesn’t always result in injury of the host i.e. disease
- classed by site of infection:
- localised - sore throat
- generalised - influenza
3
Q
outcomes of infection
A
- infection without illness
- infection will illness but no long term consequences
- infection, illness and death
- not in the microorganism’s best interest to kill the host
- host can’t transmit infection
- e.g. rabies
- humans can never transmit rabies so doesn’t matter if it dies or not - dead end so they kill host
4
Q
asymptomatic infection
A
- common
- microorganism often cannot multiply for several reasons
- temperature non-optimal
- killed by immune system
- unable to attach
- lack of food source
5
Q
recurrent illness
A
- can occur when relationship is established between host and pathogen
- host controls microorganisms but doesn’t eliminate it
- e.g. chicken pox
- remains in host for lifetime
- if host’s immune system weakens disease returns in the form of shingles
6
Q
host defences
A
- physical and mechanical barriers
- chemical barriers
- innat eimmuntiy
- acquired/adaptive immuntiy (vertebrates only)
7
Q
host toleration
A
- host allows colonisation but restricts it to certain regions where there will be no harm
- e.g. staph aureus - sore throat
- e.g. strep pneumoniae - usually restricted to pharynx, but spread to lungs causes severe disease
- progression beyond colonisation and breaching of defences = infection
8
Q
requirements of a disease-causing microorganism
A
- transmission between hosts
- entry and adherence to target tissues
- evasion of host defences and multiplication in host tissues
- obtain iron and other essential nutrients
- produce symptoms
- exit the host
9
Q
target tissue adherence
A
- shapes the infection
- different influenza strains have different surface molecules
- allow adherence to different regions of respiratory tract
- lower respiratory tract infection much more dangerous
- site of oxygen exchange
10
Q
host parasite relationships
A
- highly dynamic
- determines outcome of infection
- parasite pathogenicity and host susceptibility
- each modifies activites functions and genetics of the other
- genetic variability of both host and pathogen is important
- symptoms and severity differs between individuals
11
Q
stages of the infectious process
A
- entry
- oral, respiratory, parenteral
- attachment
- pili, capsules, proteins
- colonisation
- metabolism, replication, clearance evasion
- tissue damage
- toxins, invasion, immune repsonse
12
Q
route of entry
A
- depends on microorganism’s ability to survive in the environment
- some can survive for months
- mycobacterium - oral transmission
- some very sensitive to the environment and die upon exposure
- HIV - transmission by sexual intercourse
- some can only use arthropod vectors
- malaria
- also helps bypass main host barrier (skin)
13
Q
infection routes
A
- depend on biology of organism
- respiratory and salivary spread - aerosol transmission for more durable microorganisms
- fecal-oral spread common - humidity and nutrient availability
- animal vectors or vertebrate reservoirs
- some combine vector, vertebrate reservoir and human host
- plague, yellow fever
14
Q
attachment
A
- key factor in determining entry route and localisation within the host
- adhesion molecules must bind host cell membranes
- inability to attach to mucosa means the microorganism will die and be washed away
15
Q
colonisation
A
- involves multiplication and use of host resources
- host cell remodelling to establish closer relaitonship
- counteracting host immune system
- phagocytosis - microorganisms can:
- inhibit fusion
- escape phagolysosome
- multiply within it - mycobacterium
20
Q
kinetics of parasite-host binding
A
