02 - Infection biology Flashcards
Term: microbes that can cause disease
pathogens
Term: microbes that cause disease only in immunocompromised people
opportunistic pathogens
Term: measure of a microbe’s ability to cause disease
virulence
Term: the number of organisms required to cause disease in 50% of the population
ID50
What are the two mechanisms of bacterial pathogenesis?
- production of toxins (endotoxins and exotoxins)
2. induction of inflammation
Identify: surface protein of bacteria that mediate binding to endothelium and to extracellular proteins such as fibronectin. Give example of a bacterium that has this.
curli.
Salmonella
(Salma Hayek and her curli hair.)
Examples of enzymes involved in bacterial invasion
- collagenase and hyaluronidase
- coagulase - formation of fibrin clot coating the organism
- immunoglobulin A (IgA) protease
- leukocidin
This enzyme is considered to be primarily responsible for the development of cellulitis from a small furuncle. Another name for this enzyme?
Hyaluronidases, a.k.a. spreading factor
Enumerate: bacteria with IgA protease
Streptococcus pneumoniae
Haemophilus influenzae
Neisseria meningitidis
Neisseria gonorrhoeae
SHiNe My Gong
Identify: This virulence factor is antiphagocytic, preventing opsonization of C3b. What organism has this virulence factor?
M protein of Streptococcus pyogenes
Identify: This virulence factor prevents opsonization by preventing complement activation. What organism has this virulence factor?
Protein A of Staphylococcus aureus
Gram (-) vs Gram (+) in terms of production of exotoxins and endotoxins.
Only Gram (-) organisms can produce endotoxins. Gram (+) and some Gram (-) can produce exotoxins.
Exotoxin vs endotoxin in terms of location of genes
Exotoxin: plasmid or bacteriophage
Endotoxin: bacterial chromosome
Exotoxin vs endotoxin in terms of toxicity and antigenicity
Exotoxin: high toxicity and antigenicity
Endotoxin: low toxicity and antigenicity
Exotoxin vs endotoxin in terms of vaccine creation
eXotoxin: toXoids used as vaccine
Endotoxin: no vaccine available
Exotoxin vs endotoxin in terms of chemistry
Exotoxin: polypeptide
Endotoxin: lipopolysaccharide
Exotoxin vs endotoxin in terms of heat stability
Exotoxin: destroyed rapidly at 60 degrees C
Endotoxin: stable at 100 degrees C
Example of an exotoxin that is heat-stable?
Staphylococcal enterotoxin
Enumerate: subunits of exotoxins
- A subunit, a.k.a. active (toxic) subunit
2. B subunit, a.k.a. binding subunit
This type of exotoxin causes symptoms by causing a cytokine storm
Superantigen
Explain mechanism of toxicity of tetanospasmin. What bacterium produces this?
- exotoxin of Clostridium tetani
- hydrolyzes the synaptobrevins (VAMP), inhibiting the vesicular release of inhibitory neurotransmitters glycine and GABA
What are the components of endotoxin? Which of these is the toxic component? Where is it found?
O antigen (polysaccharide) and Lipid A (toxic component) found in the outer membrane of Gram (-) bacteria
All bacteria have cell walls composed of peptidoglycan excpet
Mycoplasma pneumoniae
All gram-positive bacteria have no endotoxin except:
Listeria monocytogenes
All bacterial capsules are composed of polysaccharide except:
What is it composed of?
Bacillus anthracis
-protein
All exotoxins are heat-labile except
Staphylococcal enterotoxin
