Chapter 2: Bacterial virulence factors and toxins Flashcards
How many pigment producing bacteria are there?
4
1) Actinomyces israelii
2) S. aureus
3) Pseudomonas aeruginosa
4) Serratia marcescens
Urease-positive bugs
“PUNCH KSS” (or CHuck Norris hates PUNKSS)
1) Proteus
2) Ureaplasma
3) Nocardia
4) Cryptococcus
5) H. pylori
6) Klebsiella
7) S. epidermidis
8) S. saprophyticus
What pigment does Actinomyces israelii produce?
“Israel has yellow sand”
Actinomyces israelii appear as yellow “sulfur” granules, which are composed of filaments of bacteria
Which microbe appears as yellow “sulfur” granules, composed of filaments of bacteria?
Actinomyces israelii
“Israel has yellow sand”
What pigment does S. aureus produce?
yellow
aereus means gold in Latin
Which microbe produces a yellow pigment?
Staph. auerus
aureus means gold in Latin
Pseudomonas aeruginosa produces what pigment?
blue-green pigment
AERUGala is green
What microbe produces a blue-green pigment?
Pseudomonas aeruginosa (AERUGala is green)
Serratia marcescens produces what color pigment?
red pigment
think red maraschino cherries for marcescens
What microbe produces a red pigment?
Serratia marcescens
think red maraschino cherries for marcescens
What is the function of the virulence factor, Protein A?
Protein A binds the Fc region of IgG and prevents opsonization and phagocytosis.
What virulence factor binds the Fc portion of IgG to prevent opsonization and phagocytosis?
Protein A
What microbe expresses IgA?
S. auerus
What is the function of the virulence factor IgA protease?
IgA protease cleaves IgA to allow certain bacteria to colonize respiratory mucosa (recall IgA antibody plays a critical role in mucosal immunity)
What virulence factor allows bacteria to evade mucosal immunity and colonize respiratory mucosa?
IgA protease
IgA protease is expressed by which bacteria? (3)
“SHiN”
1) S. pneumoniae
2) H. influenzae type B
3) Neisseria
What is the function of M protein?
M protein inhibits the action of complement to prevent phagocytosis
What virulence factor inhibits complement to prevent phagocytosis?
M protein
What microbe expresses M protein?
Group A streptococci (Strep. pyogenes)
Exotoxins are produced by what type of bacteria?
Exotoxins are released by most of the major gram-positives, and some species of gram-negative bacteria
Endotoxins are produced by which type of bacteria?
Most gram-negative bacteria (recall endotoxin, or Lipid A, is a component of LPS which is located on the outer cell membrane)
Are exotoxins or endotoxins secreted from the cell?
Exotoxins are secreted
Endotoxins are released upon lysis of gram-negative bacteria
What is the chemical composition of exotoxins versus endotoxins?
Exotoxins are composed of polypeptide.
Endotoxins are composed of lypopolysaccharide LPS
Are exotoxins or endotoxins composed of polypeptide?
Exotoxins are composed of polypeptide
Are exotoxins or endotoxins composed of lipopolysaccharide??
Endotoxins are composed of LPS
What is the difference in location of genes of exotoxins versus endotoxins?
Exotoxin genes are located in plasmids or bacteriophages.
Endotoxin genes are located on the bacterial chromosome.
Where are exotoxin genes located?
On plasmid or bacteriophage DNA
Where are endotoxin genes located?
On bacterial chromosome
Genes encoding which (exotoxin or endotoxin) are located on plasmids or bacteriophage DNA?
Exotoxin
Genes encoding which (exotoxin or endotoxin) are located on bacterial chromosomes?
endotoxin
What is the difference in toxicity of exotoxins versus endotoxins?
Exotoxins have high toxicity (fatal dose on the order of 1 ug).
Endotoxins have low toxicity (fatal dose on the order of hundreds of micrograms).
What is the difference in antigenicity of exotoxins versus endotoxins?
Exotoxins induce high-titer antibodies called antitoxins.
Endotoxins are poorly antigenic.
Are vaccines available or exotoxins or endotoxins?
Toxoids (endotoxins) used as vaccines.
No toxoids are formed for endotoxins, so no vaccine is available.
What is the difference in heat stability of exotoxins versus endotoxins?
Exotoxins are destroyed rapidly at 60C (except for staphylococcal enterotoxin).
Endotoxins are stable at 100C for 1 hr.
Which (exotoxins or endotoxins) are destroyed rapidly at 60C?
Exotoxins (except staphylococcal enterotoxins)
Which (exotoxins or endotoxins) are stable at 100C for 1hr?
Endotoxins
What are typical diseases associated with exotoxin? (3)
1) Tetanus
2) Botulism
3) Diphtheria
Tetanus, botulism, and diphtheria are associated with (exotoxin or endotoxin)?
Exotoxin
What diseases are typically caused by endotoxins? (2)
1) Meningococcemia
2) Sepsis by gram-negative rods
Meningococcemia and sepsis are typical diseases caused by (exotoxin or endotoxin)?
Endotoxin
Bacteremia - defn
bacteria in the bloodstream
Sepsis - defn
Bacteremia that causes a systemic immune response to the infection:
- high or low temperature
- elevation of WBC
- fast heart rate
- fast breathing rate
Septic shock - defn
Sepsis that results in dangerous drops in blood pressure (hypotension) and organ dysfunction (severe sepsis).
mnemonic for characteristics of endotoxin?
ENDOTOXIN
1) Edema
2) Nitric oxide
3) DIC
4) Outer membrane
5) TNF-a
6) O-antigen
7) eXtremely heat stable
8) IL-1
9) Neutrophil chemotaxis
Endotoxin (Lipid A) activates which 3 pathways?
1) macrophages
2) complement
3) tissue factor
Endotoxin activates macrophages to release what 3 endogenous mediators of sepsis? What are the associated clinical signs?
1) TNF-a - fever and hypotension
2) IL-1 - fever
3) Nitric oxide - hypotension
Endotoxin activates complement (which 2 components) which leads to what clinical signs? (2)
1) C3a - edema, hypotension
2) C5a - neutrophil chemotaxis
Endotoxin activates the C3a component of complement which leads to what clinical signs?
Edema and hypotension
Endotoxin activates the C5a component of complement which leads to what clinical sign?
Neutrophil chemotaxis
Endotoxin activates tissue factor which can lead to what clinical sign?
coagulation cascade -> DIC
What vital interventions should be performed immediately (<1 hr) of a diagnosis of sepsis?
The septic six: BUFALO
1) blood - draw blood cultures them prior to antibiotic administration
2) urine - insert urinary catheter and monitor hourly urine output
3) fluid - treat hypotension with IV fluids and drugs (dopamine and norepinephrine)
4) antibiotics - administer empiric broad spectrum antibiotics stat
5) lactate (and hemoglobin) - measure serum lactate and hemoglobin levels, associated with mortality
6) oxygen - maintain oxygenation, often with high flow O2 with intubation and mechanical ventilation
