02 - Infection biology

Question 1

Term: microbes that can cause disease

Answer 1

pathogens

Question 2

Term: microbes that cause disease only in immunocompromised people

Answer 2

opportunistic pathogens

Question 3

Term: measure of a microbe’s ability to cause disease

Answer 3

virulence

Question 4

Term: the number of organisms required to cause disease in 50% of the population

Answer 4

ID50

Question 5

What are the two mechanisms of bacterial pathogenesis?

Answer 5

1. production of toxins (endotoxins and exotoxins)

2. induction of inflammation

Question 6

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.

Answer 6

curli.
Salmonella

(Salma Hayek and her curli hair.)

Question 7

Examples of enzymes involved in bacterial invasion

Answer 7

1. collagenase and hyaluronidase
2. coagulase - formation of fibrin clot coating the organism
3. immunoglobulin A (IgA) protease
4. leukocidin

Question 8

This enzyme is considered to be primarily responsible for the development of cellulitis from a small furuncle. Another name for this enzyme?

Answer 8

Hyaluronidases, a.k.a. spreading factor

Question 9

Enumerate: bacteria with IgA protease

Answer 9

Streptococcus pneumoniae
Haemophilus influenzae
Neisseria meningitidis
Neisseria gonorrhoeae

SHiNe My Gong

Question 10

Identify: This virulence factor is antiphagocytic, preventing opsonization of C3b. What organism has this virulence factor?

Answer 10

M protein of Streptococcus pyogenes

Question 11

Identify: This virulence factor prevents opsonization by preventing complement activation. What organism has this virulence factor?

Answer 11

Protein A of Staphylococcus aureus

Question 12

Gram (-) vs Gram (+) in terms of production of exotoxins and endotoxins.

Answer 12

Only Gram (-) organisms can produce endotoxins.
Gram (+) and some Gram (-) can produce exotoxins.

Question 13

Exotoxin vs endotoxin in terms of location of genes

Answer 13

Exotoxin: plasmid or bacteriophage
Endotoxin: bacterial chromosome

Question 14

Exotoxin vs endotoxin in terms of toxicity and antigenicity

Answer 14

Exotoxin: high toxicity and antigenicity
Endotoxin: low toxicity and antigenicity

Question 15

Exotoxin vs endotoxin in terms of vaccine creation

Answer 15

eXotoxin: toXoids used as vaccine
Endotoxin: no vaccine available

Question 16

Exotoxin vs endotoxin in terms of chemistry

Answer 16

Exotoxin: polypeptide
Endotoxin: lipopolysaccharide

Question 17

Exotoxin vs endotoxin in terms of heat stability

Answer 17

Exotoxin: destroyed rapidly at 60 degrees C
Endotoxin: stable at 100 degrees C

Question 18

Example of an exotoxin that is heat-stable?

Answer 18

Staphylococcal enterotoxin

Question 19

Enumerate: subunits of exotoxins

Answer 19

1. A subunit, a.k.a. active (toxic) subunit

2. B subunit, a.k.a. binding subunit

Question 20

This type of exotoxin causes symptoms by causing a cytokine storm

Answer 20

Superantigen

Question 21

Explain mechanism of toxicity of tetanospasmin. What bacterium produces this?

Answer 21

• exotoxin of Clostridium tetani
• hydrolyzes the synaptobrevins (VAMP), inhibiting the vesicular release of inhibitory neurotransmitters glycine and GABA

Question 22

What are the components of endotoxin? Which of these is the toxic component? Where is it found?

Answer 22

O antigen (polysaccharide) and Lipid A (toxic component) found in the outer membrane of Gram (-) bacteria

Question 23

All bacteria have cell walls composed of peptidoglycan excpet

Answer 23

Mycoplasma pneumoniae

Question 24

All gram-positive bacteria have no endotoxin except:

Answer 24

Listeria monocytogenes

Question 25

All bacterial capsules are composed of polysaccharide except:
What is it composed of?

Answer 25

Bacillus anthracis

-protein

Question 26

All exotoxins are heat-labile except

Answer 26

Staphylococcal enterotoxin