PMB: Pathogenesis Flashcards
What is required for a pathogen to be able to infect?
- Their must be interaction between host and pathogen
- The Pathogen must be able to carry out the attack - be virulent
- The host must be capable of being infected (associated with a degree of being compromised)
Describe symptoms between people when infected with a pathogen/ infectious disease
- Vary in terms of severity between people
- Often vary based on tissue affected and organism
- What are the symptoms of botulism?
- What organism causes it?
- Chlostridium Botulinum
- Inital tiredness, weakened eyes, trouble speaking
- Followed by spread to weakening of limbs and chest muscles
What does virulence mean?
The capacity of a pathogen to cause disease (LD50)
What is infectivity?
The number of organisms required to cause infection
What does severity mean?
The impact on the host. Can range from acute to causing death
What are factors which affect virulence?
- Age of individual
- Immune status
- Presence of other conditions
- Enviromental conditions
- Temp, time of year
What does a pathogen need to do to infect?
Must gain entery to the body and reach the approproate tissue
- What are weakness where pathogens are likely to gain entery?
- What are altenrative sites of entery?
- Eyes, Ears, other parts of skin (e.g. piercings)
- Cut and insect bites
After entery to the body what are the next steps for the pathogen to cause succesful infection
Following exposure to a pathogen, the pathogen must:
- Adhere to the organism
- Invade the tissue
- Evade the defence mechanism
- Cause disease
Describe the adhering process
- Different approaches
- Selective or non-selective
- Capsules and slime layers
- Fimbriae and pili provide cell surface attachment via selective proteins
- Inital point of conact is not enough, what else is required
- What is needed for this?
- The pathogen must multiply to have enough organisms to cause infection
- For the pathogen to survive sufficent nutriets are required. The provision of iron is cruicial. MAny bacterial pathogens often secrete siderophages which have a high affinity for iron
Where does the bacteria go once infection site reached?
- Some stay locally
- Others spread to other parts of the body
- Bacteriaemia - spread of bacteria in the blood stream
- Can result in blood-borne systemic infections (septicaemia)
What do some pathogens produce to enhance infection?
- Virulence Factors (VFs)
- These enchance virulence either directly or indirecly
What type of molecule are most Vfs?
Enzymes
