Chapter 15 Micro

Question 1

What is pathogenicity?

Answer 1

The ability to cause disease, a property of the organism that it either has or lacks

Question 2

What is virulence?

Answer 2

The extent of pathogenicity, a measurement of the degree of pathogenicity that it can be assessed

Question 3

What are mucous membranes?

Answer 3

lining respiratory tract, gastrointestinal tract, genitourinary tract, conjunctiva

Question 4

What are the portals of entry related to skin?

Answer 4

hair follicles, sweat glands, surface

Question 5

What are the portals of entry related to the parenteral route?

Answer 5

(not parental) – due to penetration or injury
regardless of anatomical site of entry
Preferred portal of entry
“preferred” by the organism, not by us

Question 6

What is ID50?

Answer 6

Infectious dose for 50% of the test population

Question 7

What is LD50?

Answer 7

Lethal dose (of a toxin) for 50% of the test population

Question 8

What is adherence?

Answer 8

Adhesins or ligands on the microbe bind to receptors on host cells
Ex: glycocalyx, fimbriae, M protein

Question 9

What are biofilms?

Answer 9

-communities of adherent microbes
-an aggregate of microbes stick to each other
and to a substrate (surface)
-adhere to most surfaces with organic matter, a mix of polysaccharides and proteins
-involved in 65% of human bacterial infections

Question 10

What are capsules?

Answer 10

• capsules are not required but increase virulence of bacteria that have them
• preventing phagocytosis by immune system cells
• Can be targeted by antibodies

Question 11

What is an M protein?

Answer 11

resists phagocytosis

-Strep. pyogenes

Question 12

What is opa protein?

Answer 12

inhibits T helper cells

-Neisseria gonorrhoeae

Question 13

What is mycolic acid?

Answer 13

(waxy lipid) resists digestion

Mycobacterium tub.

Question 14

What are exo enzymes?

Answer 14

enzymes that work outside the bacterium to increase virulence

Question 15

What is coagulase?

Answer 15

Coagulates fibrinogen

Question 16

What are kinases?

Answer 16

Digest fibrin clots

Question 17

What is hyaluronidase?

Answer 17

Hydrolyzes hyaluronic acid

Question 18

What is collagenase?

Answer 18

Hydrolyzes collagen

Question 19

What are IgA proteases?

Answer 19

Destroy IgA antibodies

Question 20

What are invasins?

Answer 20

• Type of penetration of the host cell cytoskeleton
• Salmonella alters host actin to enter a host cell
• causes membrane ruffling

Question 21

How does penetration into the host cell occur?

Answer 21

Use actin to move from one cell to the next

Question 22

What does antigenic variation do?

Answer 22

• Alter surface proteins

- Surface proteins are encoded by genes that change

Question 23

How do pathogens damage host cells?

Answer 23

• deplete host’s nutrients
• cause direct damage
• synthesize toxins
• cause immune reactions

Question 24

What are siderophores?

Answer 24

siderophores chelate host’s iron and allow the bacteria to take it up

Question 25

What is direct damage?

Answer 25

disrupt host cell function
produce problematic waste products
action of toxins
Of the ~220 known bacterial toxins, about 40% cause disease by damaging eukaryotic cell membranes
Many toxins, such as botulism toxin (botox) is a neurotoxin, that is they target and inhibit the function of neurons.

Question 26

What are toxins?

Answer 26

Substance that contributes to pathogenicity

Question 27

What is toxigenicity?

Answer 27

Ability to produce a toxin

Question 28

What is toxemia?

Answer 28

Presence of toxin in the host’s blood

Question 29

What is a toxoid?

Answer 29

Toxoid: Inactivated toxin used in a vaccine

Question 30

What are antitoxins?

Answer 30

Antibodies against a specific toxin

Question 31

What are exotoxins?

Answer 31

Toxins target specific structure on or in the host cell

Question 32

What are membrane disrupting toxins?

Answer 32

Lyse host cells by making protein channels in the plasma membrane

Question 33

What are some examples of of membrane disrupting toxins and what do they do?

Answer 33

• Leukocidins: kill phagocytic leukocytes
• Hemolysins: destroy erythrocytes
• Streptolysins: lyse RBC
• Disrupt phospholipid bilayer

Question 34

What are superantigens?

Answer 34

• Cause an intense immune response due to release of cytokines from host cells stimulating proliferation of T cells
• this reaction disables the host immune system
• Symptoms: fever, nausea, vomiting, diarrhea, shock, and death

Question 35

What is diphtheria toxin?

Answer 35

Corynebacterium diphtheriae
lysogenic phage caries tox gene
tox encodes an A-B exotoxin
causes diptheria, an upper respiratory tract disease
can cause severe skin lesions
part of the DPT vaccine

Question 36

What are erythrogenic toxin?

Answer 36

Streptococcus pyogenes
superantigen
damages plasma membranes of capillaries in skin
causes Scarlet Fever, characterized by red skin rash

Question 37

What is botulinum toxin?

Answer 37

Clostridium botulinum
A-B exotoxin
neurotoxin, inhibits acetylcholine
acts at the neuromuscular junction, preventing transmission of impulses from the nerve to the muscle, flaccid paralysis

Question 38

What is tetanus toxin?

Answer 38

Clostridium tetani
A-B exotoxin
neurotoxin
causes uncontrollable muscle contractions
“lockjaw”

Question 39

What is vibrio enterotoxin?

Answer 39

Vibrio cholerae
A-B exotoxin
enterotoxin
B subunit binds epithelial cells causes cells to secrete fluids and electrolytes
severe diarrhea

Question 40

What is staph enterotoxin?

Answer 40

Staphylococcus aureus
superantigen
toxic shock syndrome

Question 41

What are endotoxins?

Answer 41

outer portion of cell wall gram neg

• LPS
• cause macrophages to make cytokines

Question 42

LAL assay

Answer 42

Limulus amoebocyte lysate assay
detects very small amounts of endotoxin
amoebocyte (blood cell) lysis produces a clot
Endotoxin causes lysis

Question 43

What are portals of exit?

Answer 43

Earwax, blood, skin flakes, feces, tears, secretion, saliva

Question 44

Pathogenesis of SARS COV 2

Answer 44

SARS-CoV-2 infects the upper respiratory tract (sinuses, nose, and throat) and the lower respiratory tract (windpipe and lungs).
Its receptor ACE2 is abundant in type II alveolar cells of the lungs.
As alveolar disease progresses, respiratory failure and can follow.
It is not clear whether SARS-CoV-2 is able to infect and cause pathology in the nervous system.
The virus also affects gastrointestinal organs. ACE2 is abundant on cells of gut epithelium.
The virus can cause acute myocardial injury and chronic damage to the cardiovascular system.
A common cause of death is complications related to the kidneys.

Question 45

What are cytopathic effects of viruses?

Answer 45

transformed cells, loss of contact inhibition

Question 46

What is viral pathogenesis?

Answer 46

cytopathic
shut-down of host macromolecular synthesis, cell lysis
lysozymes - triggered inside cells, consume from within
inclusion bodies - aggregates visible inside cells
syncytium - fusion of cells, create single cells with multiple nuclei
apoptosis (programmed cell death)
non-cytopathic (change cell function, behavior)
transformation
inhibition of apoptosis (programmed cell death)
immortalization, loss of contact-inhibition
can lead to cancer
immune response
inflammation, interferon
auto-immunity

Question 47

What is the action of an A-B exotoxin?

Answer 47

1.bacterium produces and releases exotoxin
2. B binding component of exotoxin attaches to the host cell receptor
3. A-B exotoxin enters the cell by endocytosis
4. A-B exotoxin enclosed in pinched off portion of plasma membrane during pinocytosis
5. A-B components of exotoxin sep. The A component alters cell by inhibiting protein synthesis
B component is released from host cell

Question 48

What are some diseases passed via the fecal oral route?

Answer 48

Poliomyelitis
Hep A 
Rotvirus 
Shigellosis
Typhoid fever 
Cholera
C. diff