Microbial pathogenicity Flashcards
What would happen if a person had not immune system/ a weak one?
- Lot’s of microbes would grow
- They would use the body as food
- The weaker the immune system, the more opportunity for microbes to infect
What is an example of a virus?
H1N1 Influenza
- A single stranded RNA, enveloped virus
HIV virus –> causes AIDS disease
How does influenzas envelope cause the need of new vaccines?
They are coated with a range of different proteins, that constantly change due to mix and match of RNA
- Different receptors means different areas of the body it can infect
- Therefore, new vaccines are needed
What is an example of fungi?
Trichophyton spp (causes ringworm)
What is an example of prions?
Kuru (laughing disease)
What are prions?
Misfolded proteins
- A normal protein and a misfolded protein interacts and causes it to turn into a misfolded protein
What is an example of a protozoa?
Plasmodium spp (malaria parasites)
What is an example of Helminths?
Ancylostoma duodenale (hookworm)
What is an example of a bacteria?
Bacillus anthracis
- Gram positive
- Endospore fomring
- Rod shaped
What is an endospore?
A dormant form of bacteria
- Forms an endospore when its in bad conditions
- kills off its vegetative state to from endospore
- Can live for a long time in this form under bad conditions
What are gram positive bacteria?
- Have thick cell walls that consist primarily of peptidoglycan
- Peptidoglycan traps and retains crystal violet stain
- Have plasma membrane
What are gram negative bacteria?
- Do not retain the stain, crystal violet is easily rinsed away
- Have cell walls with two layers, a thin peptidoglycan layer and a thick out membrane that contains polysaccharides bonded to lipids
- Have a plasma membrane
What are Koch’s postulates?
Guidelines used to demonstrate that a specific pathogen causes specific disease symptoms
What are the rules of Koch’s postulates?
- The pathogen must be present in every individual with the disease
- A sample of the microorganism taken from the diseased host can be grown in pure culture
- A sample of the pure culture causes the same disease when injected into a healthy host
- The microorganism can be recovered from the experimentally infected host
What are some exceptions of Koch’s postulates?
- Microbes that can’t be cultures e.g. syphilis bug (Treponema pallidum)
- Pathogens that also can be found in health subjects e.g. Vibrio cholera
What is an infection?
About how the bacteria/ virus can get into the body
What are the 3 stages of infection?
- Adherence to host cells
- Invasion of host tissues
- Replication within host tissues
What is disease?
Causing damage to host tissues due to infection
- Toxins are also produced
What is the bacterial virulence factor that relates to Adherence to host cells?
Adhesions such as fimbriae (bind to host cells e.g. Neisseria gonorrhoeae
- Hair-like projections that are very sticky
What is the bacterial virulence factor that relates to Invasion of host tissues
Motility (moving through mucus) e.g. helicobacter pylori (responsible for stomach ulcers)
- Flagella
What is the bacterial virulence factor that relates to Replication within host tissues?
Siderophores (bind iron) Yersinia pestis e.g. the siderophore yersiniabactin solublises metal bound to host proteins and transports it back to the bacteria
Capsules (resist phagocytosis from white blood cells) e.g. streptococcus pneumoniae
Avoids the immune system
What is the bacterial virulence factor that relates to disease?
Endotoxins = cause inflammation Exotoxins = can be fatal
What are endotoxins?
Are lipopolysaccharides (LPS) components found in the outer membrane of gram-negative bacteria, and elicit strong immune responses
What are some factors of endotoxins?
They are only released when the bacteria is destroyed
- Sparks inflammation when released
How can we know what type of virulence factor the bacteria causes?
Gram negative and gram positive test
What are exotoxins?
Are produced within living bacteria, and then released into the surrounding medium while they are still alive.
What are the three types of exotoxins?
Cytotoxins, Neurotoxins and enterotoxins
What are Cytotoxins?
Strepholysin which is a extracellular enzyme is produced by the bacteria such as staphylococcus pyogenes which causes the complete lysis of red blood cells (Beta hemolysis)
What are Neurotoxins?
Botulinum produced by the bacteria such as Clostridium botulinum which causes paralysis
- Very deadly
- Stops neurotransmitters from being released from the axon terminal
What are enterotoxins?
Shiga toxin is produced by the bacteria Shigella dysenteriae and causes severe dysentery (infectious diarrhea)
- Spreads through contaminated food and water
