The pathogenesis of bacterial infections Flashcards
(43 cards)
What is pathogenesis?
Pathogenesis involves all the cellular events leading to the development of disease
What is the definition of a pathogen?
an organism that has the ability to cause disease
What causes peptic-ulcer disease?
Stress/Environmental factors
What bacteria causes peptic ulcers?
H.Pylori
What are three reasons why infections are not in all hosts in the population?
- Infection depends on host factors as well as bacterial factors
- Differences in hosts range (wide vs limited)
- Even among the host range some can be resistant whilst others are susceptible
What is pathogenicity?
An ability to cause disease (damage the host)
What is Virulence?
The degree of pathology caused by the organism/ infection
What is infectivity?
The capacity for transmission and spreading to new hosts
What can effect infectivity?
- Type of pathogen
- Dosage/ Inoculum
- Host factors
- Environmental factors
- Virulence: Species, Strain
What is transmissibility?
- Capacity to grow in parts of the body
- Capacity to readily exit an infected host
- Capacity to survive in transition between hosts
(sporulation, environment and arthropod-borne infections)
What are the two different sources of infection?
Exogenous and Endogenous
What are exogenous sources of infections?
Mainly true pathogens
What are endogenous sources of infections?
Opportunistic pathogens and persistent true pathogens
What is the first step of a succesful bacteria pathogen?
Attachment to and entry into the host body
The movement through fluids is mediated by the flagella
What are the helical structures that extend from the bacteria made up from?
They are long helical structures that extend outward from the surface of the cell
composed of polymerisation of flagellin protein
evolutionarily conserved
What are some routes of entry for bacteria?
Skin and extended mucosa (direct contact)
Body orifices e.g eye/ear reproductive/urinary tract
Direct injection into the blood stream (arthropod-borne infections)
What is the second step for a succesful bacterial pathogen?
Bacterial pathogens often bind to a niche to gain entry into tissue and have to evade host defences
Why can it be a struggle for bacteria to enter into a host cell?
Many parts of the body are protected by mucin which acts as a lubricant and also traps bacteria (prevents microbes from gaining access/ binding to the first layer of cells)
mucin= mesh of proteins and polysaccharides
What are some strategies bacteria can use to evade host defences?
- molecular mimicry
- switching off “irritants”
- hiding inside epithelial/ immune cells
- prevention of activity immune response
What is the third step for a succesful bacteria pathogen?
Multiplication and Spread
Once the bacteria have entered/ passed the dermal and mucin layers they can either become an extracellular or intracellular pathogen
What is the 4th step in being a succesful bacterial pathogen?
Damage to the host and therefore inducing disease
What are some of the mechanisms that can be used to induce disease?
- lysis of host cells/tissues via toxins or invasion
- disruption of the immune system
- disruption of the barrier function
- disruption of the local mciroflora
What is the fifth step of a succesful bacterial infection
Transmission to a new susceptible host
What are some ways the immune system can respond after damage through secretion of toxins?
- Creates pus (proteins, dead cells, host cells)
- Spreading factors, proteins like DNases and proteases facilitate spread into neighbouring tissue
