Microorganisms and their properties Flashcards
List in size order, smallest to largest, the microorgansims that can cause infection.
Prions Viruses Bacteria (prokaryote) Fungi (eukaroyte) Parasites (eukaryote)
What is a prion?
Infectious particles of mutant proteins that induce misfolding of host proteins.
Where are normal human prion proteins located?
Within neural tissue and tonsils.
How are these normal prion proteins affected?
PrPc converted to mutant Prscrapie that fold to form amyloid fibres that deposit in the brain, causing progressive neurodegenerative disease. Loss of motor control and disinhibition.
PrBSE = mad cow disease causing lesions and vacuoles in the brain
How are prions transmitted?
Resistant to disinfectants and heat. Usually transmitted from animals through meat which becomes mutant when encounters the PrPsc variant.
What is a virus?
An intracellular obligate parasite. It is DNA or RNA within a capsid and in some cases an envelope.
Why does a virus require a host?
To replicate within the host using its apparatus for the production of new virus proteins. RNA viruses have the ability to integrate into the genetic material.
What can a virus cause?
Degeneration, cell lysis, cell fusion and synyctia formation, cell proliferation, latency
What is bacteria?
Can be found externally to a host. Most is beneficial until it enters the wrong environment.
What is an obligate, opportunistic and commensals bacteria?
Obligate = Always pathogenic e.g. TB, salmonella Opportunistic = Can be pathogenic Commensals = Never pathogenic
What is the structure of a bacteria?
A prokaryote with no membrane bound organelles. Have a rigid cell wall of peptidoglycans.
What type of cell walls can a bacteria have?
Gram -ve wall = a DOUBLE membrane with a THIN layer of peptidoglycans e.g. Ecoli
Gram +ve wall = a SINGLE membrane with a THICK layer of peptidoglycans e.g. staphylococci, streptococci
How can gram -ve be distinguished from gram +ve?
-ve stains PINK
+ve stains PURPLE
How does bacteria cause damage in the host?
Produces exotoxins or causes direct tissue damage through invasion.
What are symptoms?
The response of the immune system to a pathogen
What is the bacterial cell wall composed of?
Peptidoglycans to form the shape and structure.
Lipoteichoic acid is an immune irritant of gram +ve that causes septic shock.
Lipopolysaccharide/LPS is an endotoxin of gram -ve that is an immune stimulator that causes sepsis.
Lipid A is found on LPS in gram -ve that causes toxic shock.
Which part of bacteria mutates when under pressure of treatment?
The polysaccharides in LPS act as O antigens that mutate
What features can a bacteria have?
Flagellum - For chemotaxis movement
Pilli/Fimbrae - Allow attachment to host cells. Sex pilli allow transfer of plasmid DNA between bacteria = spread of antibiotic resistance.
Capsule - Protects from phagocytosis
Why are infants more susceptible to infections to sugary microbes?
Response to sugary microbes isn’t fully developed and the capsule is preventing phagocytosis.
What are fungi?
A single or multicellular eukaryote that contains membrane bound organelles surrounded by a cell wall of polysaccharide chitin and glucans.
How do most fungi grow?
As Hyphae - cyclindrical tubes that interconnect to form mycelium. Can produce fruiting bodies or spores.
What is the cause of thrush?
Candida albicans in moist, slightly acidic environments.
Where are fungi likely to infect?
Skin and respiratory tract but can cause systemic infection in immunocompromised Pts.
