Lecture 14

Question 1

How do microorganisms enter a host?

Answer 1

• mucous membranes
• skin
• parenteral route (deposited directly into tissues when barriers are penetrated)

Question 2

What is ID50?

Answer 2

infectious dose for 50% of a sample population
- measures virulence of microbe

Question 3

What is the portal of entry and ID50 for bacillus anthracis?

Answer 3

skin: 10-50 endospores
inhalation: 10k-20k endospores
ingestion: 250k-1m

Question 4

What is LD50?

Answer 4

lethal dose for 50% of a sample population
- measures potency of a toxin

Question 5

What does lower LD50 values indicate?

Answer 5

higher toxicity or virulence
- takes a smaller dose to kill 50% of the population

Question 6

What does a higher LD50 value indicate?

Answer 6

lower toxicity
- larger dose is required to kill 50% of the population

Question 7

What is the LD50 of botulinum?

Answer 7

0.03 ng/kg

Question 8

What is the LD50 of shiga toxin?

Answer 8

250 ng/kg

Question 9

What is the LD50 of staphylococcal enterotoxin?

Answer 9

1350 ng/kg

Question 10

What is adherence?

Answer 10

almost all pathogens attach to host tissues

Question 11

What are adhesins?

Answer 11

ligands on the pathogen that bind to receptors on the host cells
- glycocalyx
- fimbriae

Question 12

What do capsules do?

Answer 12

impairs phagocytosis

Question 13

Give examples of bacteria and the diseases they lead to.

Answer 13

• streptococcus pneumoniae: pneumonia
• Haemophiles influenzae: pneumonia and meningitis
• bacillus anthracis: anthrax
• Yersinia pestis: plague

Question 14

Where is glycocalyx found?

Answer 14

around the cell wall

Question 15

What is in the cell wall? What are each of their functions?

Answer 15

• M protein resists phagocytosis
• Opa protein allows attachment to host cells
• Waxy lipid (mycolic acid) resists digestion

Question 16

What does coagulase do?

Answer 16

coagulates fibrinogen

Question 17

What do kinases do?

Answer 17

digests fibrin clots

Question 18

What does hyaluronidase do?

Answer 18

digests polysaccharides that hold cells together

Question 19

What does collagenase do?

Answer 19

breaks down collagen

Question 20

What does IgA protease do?

Answer 20

destroys IgA antibodies

Question 21

What is legionella pneumophila? How is it contracted?

Answer 21

• causes pneumonia
• infects lungs through inhalation (would not survive any other way of transmission)

Question 22

What is bacillus anthracis? What are the ports of entry?

Answer 22

• causes anthrax
• skin, inhalation, ingestion

Question 23

What are invasins? What do they cause?

Answer 23

• surface proteins produced by bacteria that rearrange actin filaments of the cytoskeleton
• cause membrane ruffling

Question 24

What bacteria uses actin to move from one cell to the next?

Answer 24

shigella
listeria

Question 25

How do bacteria survive inside phagocytes?

Answer 25

- low pH in phagolysosome - escape from phagosome before lysosomal fusion - prevention of fusion of lysosome with phagosome

Question 26

How do biofilms help evade phagocytes?

Answer 26

- biofilm bacteria is more resistant to phagocytosis - shielded by extracellular polymeric substance of biofilm

Question 27

What nutrient is needed for most pathogenic bacteria?

Answer 27

iron

Question 28

What are siderophores?

Answer 28

proteins secreted by pathogens that bind iron more tightly than host cells

Question 29

What are examples of direct damage?

Answer 29

- disrupts host cell function - uses host cell nutrients - produces waste products - multiplies in host cells and causes ruptures

Question 30

What are toxins?

Answer 30

poisonous substances produced by microorganisms

Question 31

What can toxins cause?

Answer 31

fever, cardiovascular problems, diarrhea, shock

Question 32

What is toxigenicity?

Answer 32

ability of a microorganism to produce a toxin

Question 33

What is toxiemia?

Answer 33

presence of toxin in the host's blood

Question 34

What is intoxication?

Answer 34

presence of toxin without microbial growth

Question 35

What are exotoxins? What do they do?

Answer 35

proteins produced and secreted by bacteria - soluble in bodily fluids - destroys host cells - inhibits metabolic functions

Question 36

What are antitoxins?

Answer 36

antibodies against specific exotoxins

Question 37

What are toxoids?

Answer 37

inactivated exotoxins used in vaccines

Question 38

What do genotoxins damage? What does this cause?

Answer 38

damages DNA - causes mutations - disrupts cell division - leads to cancer

Question 39

Why do superantigens cause an intense immune response? What are symptoms they cause?

Answer 39

- release of cytokines from host cells (T cells) - causes fever, nausea, vomiting, diarrhea, shock, death

Question 40

What is each component on a A-B toxin?

Answer 40

A: enzyme B: binding component

Question 41

What do leukocidins do?

Answer 41

kill phagocytic leukocytes

Question 42

What do hemolysins do?

Answer 42

kill erythrocytes by forming protein channels

Question 43

What do streptolysins do?

Answer 43

same as hemolysins (kill erythrocytes by forming protein channels) - just produced by streptococci instead

Question 44

What are endotoxins?

Answer 44

portion of lipopolysaccharides of gram-negative bacteria (lipid)

Question 45

When are endotoxins released? What do they do?

Answer 45

released during bacterial multiplication and when gram-negative bacteria die - stimulate macrophages to release cytokines - cause disseminated intravascular coagulation

Question 46

What test is used for endotoxins?

Answer 46

limulus amebocyte lysate assay (LAL) - horseshoe crab blood

Question 47

How does the LAL assay work?

Answer 47

amebocytes lyse in the presence of endotoxins and produce a clot

Question 48

What do plasmids carry?

Answer 48

genes for toxins, production of antibiotics and enzymes

Question 49

What is lysogenic conversion?

Answer 49

changes characteristics of a microbe due to incorporation of a prophage

Question 50

What are some examples of cytopathic effects?

Answer 50

- stopping cell synthesis - causing cell lysosomes to release enzymes - creating inclusion bodies in the cell cytoplasm - fusing cells to create a syncytium - changing host cell function or inducing chromosomal changes - inducing antigenic changes on the cell surface - loss of contact inhibition in the cell, leading to cancer

Question 51

What are alpha and beta interferons produced by? What do they do?

Answer 51

produced by virally-infected cells - protects neighboring cells from viral infection - inhibits synthesis of viral proteins and host cell proteins - kill virus-infected host cells by apoptosis

Question 52

What is fungi? What can they cause?

Answer 52

toxic metabolic product - can cause allergic response

Question 53

What do trichothecene toxins do?

Answer 53

inhibit protein syntehsis

Question 54

What do proteases do?

Answer 54

modify host cell membranes

Question 55

What do capsules do?

Answer 55

prevents phagocytosis

Question 56

What is ergot?

Answer 56

alkaloid toxin that causes hallucinations

Question 57

What is aflatoxin?

Answer 57

carcinogenic toxin produced by aspergillus

Question 58

What are mycotoxins?

Answer 58

produced by mushrooms and are neurotoxic

Question 59

Give examples of mycotoxins.

Answer 59

Phalloidin Amanitin

Question 60

How do protozoa avoid host defenses?

Answer 60

- digesting cells and tissue fluids - growing in phagocytes - antigenic variation

Question 61

What are helminths? What do they do?

Answer 61

parasitic worms - use host tissue for growth - produce large masses - cause cellular damage - produce waste products that cause symptoms

Question 62

What neurotoxin can some algae produce?

Answer 62

saxitoxin - paralytic shellfish poisoning

Question 63

What are examples of portals of exit?

Answer 63

- respiratory tract (cough/sneeze) - gastrointestinal tract (poop and spit) - genitourinary tract (pee and cum) - skin - blood