Chapter 25 - Bacterial Mechanisms of Pathogenicity

Question 1

pathogenesis

Answer 1

how pathogens cause disease

Question 2

Where Koch’s postulates do not fit

Answer 2

• some pathogens found in healthy people

- all healthy test subject equally susceptible to disease but may not have the same signs and symptoms

Question 3

pathogens

Answer 3

microbial parasites

Question 4

pathogenicity

Answer 4

the ability of a parasite to inflict damage on the host

Question 5

virulence

Answer 5

measure of pathogenicity; relative ability of a pathogen to cause disease

Question 6

opportunistic pathogen

Answer 6

causes disease only in the absence of normal host resistance

Question 7

infection

Answer 7

situation in which a microorganism is established and growing in a hot, whether or not the host is harmed

Question 8

disease

Answer 8

damage or injury to the host that impairs host function

Question 9

How can virulence be measured?

Answer 9

-from experimental studies of LD50

Question 10

LD50

Answer 10

• lethal dose 50

- the amount of an agent that kills 50% of the animals in a test group

Question 11

Highly virulent pathogens show _______________ in the number of cells required to kill 100% of the population as compared to 50% of the population

Answer 11

little difference

Question 12

toxicity

Answer 12

organisms produces a toxin that inhibits host cell function or kills host cells

Question 13

invasiveness

Answer 13

ability of a pathogen to grow in host tissue at densities that inhibit host function
-can cause damage without producing a toxin

Question 14

attenuation

Answer 14

decrease or loss of virulence (measles, mumps, rubella, rabies vaccine)

Question 15

Step One in Pathogenesis: Adherence

Answer 15

-bacteria and viruses adhere specifically yo epithelial cells through macromolecular interactions on the surfaces of the pathogen and host cell

Question 16

How is bacterial adherence facilitated?

Answer 16

• slime layer, capsule

- fimbriae, pili

Question 17

Step 2 - Invasion

Answer 17

pathogens produce various virulence factors that enhance invasiveness
-enzymes, coagulants

Question 18

Step 3 - Colonization and Infection

Answer 18

pathogens may grow locally at the site of invasion or spread throughout the body; availability of nutrients is most important in affecting pathogen growth

Question 19

bacteremia

Answer 19

presence of bacteria in the bloodstream

Question 20

septicemia

Answer 20

bloodborne systemic infection

Question 21

Genes that direct invasion are clustered together on the chromosome as…

Answer 21

pathogenicity islands

Question 22

SPI1

Answer 22

encodes proteins promoting invasion forming an injectisome type III secretion system

Question 23

SPI2

Answer 23

genes that promote a more systemic disease

Question 24

exotoxins

Answer 24

toxic proteins released from the pathogen as it grows

Question 25

3 categories of exotoxins

Answer 25

cytolytic, AB, superaktigen

Question 26

toxicity

Answer 26

ability of microorganism to cause disease as a result of a preformed toxin that inhibits host function or kills host cells

Question 27

coagulase (E)

Answer 27

a toxin found in staph that induces fibrin clotting

Question 28

streptokinase (E)

Answer 28

toxin found in strep that dissolves fibrin clots

Question 29

hyaluronidase (E)

Answer 29

toxin found in strep that dissolves hyaluronic acid (glue that cements cells together) in connective tissue

Question 30

injectisome

Answer 30

toxin found in salmonella that injects toxins into host cells

Question 31

4 classes of exoenzymes

Answer 31

glycohydrolases, nucleases, phospholipase, proteases

Question 32

glycohydrolases

Answer 32

degrades hyaluronic acid that cements cells together to promote spreading through tissues -hyaluronidase

Question 33

nucleases

Answer 33

degrades DNA released by dying cells (bacteria and host cells) that can trap the bacteria, thus promoting spread -DNAse

Question 34

phospholipases

Answer 34

degrades phospholipid bilayers of host cells, causing cellular lysis, and degrade membrane of phagosomes to enable escape into the cytoplasm -phospholipase C

Question 35

proteases

Answer 35

degrades collagen in connective tissue to promote spread | -collagenase

Question 36

2 types of superantigens

Answer 36

- toxic shock syndrome toxins - streptococcal mitogenic exotoxin - streptococcal pyrogenic toxin

Question 37

superantigens

Answer 37

stimulates excessive activation of immune system cells and release of cytokines from immune system cells -results in life-threatening fever, inflammation, and shock

Question 38

cytolytic toxins (cytotoxins)

Answer 38

work by degrading cytoplasmic membrane integrity, causing cell lysis and death

Question 39

hemolysins

Answer 39

toxins that lyse RBCs

Question 40

staphylococcal a-toxin

Answer 40

kills nucleated cells and lyses erythrocytes -7 subunit pore which causes influx of extracellular components into the cell and efflux of cytoplasmic components out of the cells

Question 41

membrane disrupting toxins

Answer 41

- streptolysin - pneumolysin - alpha-toxin (staph and clostridium) - phospholipase C - beta-toxin

Question 42

3 types of membrane disrupting toxin that assemble into pores in cell membranes, disrupting them and killing the cell

Answer 42

streptomycin, pneumolysin, a-toxin

Question 43

membrane disrupting toxin phospholipase that degrade cell membrane phospholipids, disrupting function and killing cell

Answer 43

a-toxin, phospholipase C, b-toxin

Question 44

AB exotoxins

Answer 44

consists of two subunits (A and B) | -work by binding to host cell receptor (B) and transferring damaging agent (A) across the cell membrane

Question 45

examples of AB exotoxins

Answer 45

dipththeriae toxin, tetanus toxin, botulinum toxin

Question 46

4 types of intracellular targeting toxins

Answer 46

cholera toxin, tetanus toxin, botulinum toxin, diphtheria toxin

Question 47

cholera toxin

Answer 47

activation of adenylate cyclase in intestinal cells, causing increased levels of cAMP and secretion of lfuids and electrolytes out of cell, causing diarrhea

Question 48

tetanus toxin

Answer 48

inhibits release of inhibitory neurotransmitters in CNS, causing spastic paralysis

Question 49

botulinum toxin

Answer 49

inhibit release of acetylcholine from neurons, resulting in flaccid paralysis

Question 50

diphtheria toxin

Answer 50

inhibition of protein synthesis, causing cellular death

Question 51

enterotoxins

Answer 51

- AB toxin - affects small intestine - cause massive secretion of fluid into intestinal lumen, resulting in vomiting and diarrhea - less toxic than exotoxins

Question 52

lipopolysaccharide

Answer 52

portion of cell envelope of certain gram-neg bacteria which is a toxin when solubilized

Question 53

limulus amoebocyte lysate (LAL) assay

Answer 53

can detect presence of endotoxins