Principles of Infection 2 Flashcards
Steps to becoming unwell with an infection
- Transmission
- Infection
- Pathogenicity
- Virulence
what happens at the transmission step?
host has to acquire the organism
what happens at the infection step?
the organism has to reproduce inside the host
what happens at the pathogenicity step?
organism interacts with the host in a way that causes diseases
what happens at the virulence stage?
organism causes a disease of varying severity
example of air-borne spread
aerosols or droplets from cough etc
examples of person to person spread
direct e.g. skin infection, STDs
Examples of faceo-oral spread
most often via food/ water e.g. cholera
examples of consumption of infected material transmission
e.g. salmonella, tapeworm
example of vector-borne disease transmission
mosquitos spread malaria & zika infection
example of endogenous infection transmission
from movement of own microbiome e.g. colonic bacteria to urine
example of direct inoculation transmission
e.g. open fracture, bite form infected animal
how do microorganisms cause disease?
indirect damage by host immune response and direct damage by the pathogen
How does the host immune response cause indirect damage?
- inflammation causes tissue damage & lost of normal function
- systemic response to infection can cause organ failure and death
How does a pathogen cause direct damage?
- viral reproduction causes cell lysis ( cell breakdown)
- Bacteria secrete toxins causing cell damage
How do microorganisms evade the immune system?
- Adhere (stick) to the epithelium
- Invade epithelial cells / cross epithelial barrier
- Evade innate immune cells
- Evade adaptive immune cells and antibodies
define virulence factors:
components or structure of microorganisms that helps in establishment of disease or infection (essentially to assist microorganism to colonise)
virulence factors include factors that allow microorganisms to:
- Adhere to and invade host tissues
- Evade host defences
- Proliferate in the host
- Cause damage
- Produce toxins
- host- pathogen interaction
tiny hairs on bacteria are called?
pili
Define adhesins
(on bacteria that) allows them to stick onto epithelial cells & stops them from being swept away
Define adhesins and pili
pili- tiny hairs (on bacteria that) and adhesins allow them to stick onto epithelial cells & stops them from being swept away
Some bacteria secrete enzymes which do what?
degrade the host molecules by attacking the epithelial barrier (e.g. breaking down tight junctions)