Epidemiology and Pathogenesis

Question 1

In addition to IDing the microbe, what else must be done to conclude that a microbe causes a particular disease?

Answer 1

ID the strain’s virulence factors and genes for virulence

Question 2

What does the term Incidence mean in epidemiology?

Answer 2

new cases

Question 3

What does the term prevalence mean in epidemiology?

Answer 3

total cases

Question 4

How is endemic disease characterized?

Answer 4

By regional location and periodic outbreaks

Question 5

How are epidemic and pandemic diseases characterized?

Answer 5

By…
-widespread occurrence (scale is definitive)
-rapid outbreak

Question 6

What is a reservoir?

Answer 6

Where the disease is when it is not happening (active)

Question 7

What are disease reservoirs considered?

Answer 7

Sources of ongoing infection/”where pathogens come from”

Question 8

What are human reservoirs?

Answer 8

ill persons/carriers

Question 9

What are nonliving reservoirs?

Answer 9

soil, waters air

Question 10

What are animals and vectors-living character of disease that is not human?

Answer 10

ticks, mosquitos, etc

Question 11

What is direct contact transmission?

Answer 11

by physical contact with infected person/animal (can be vertical or horizontal)

Question 12

What is indirect contact transmission?

Answer 12

by contact with a contaminated material (fomite)

Question 13

What is droplet contact transmission?

Answer 13

contaminated droplets contact membranes (short range)

Question 14

What is vehicle transmission?

Answer 14

by exposure to contaminated water/air/food (may involve fecal-oral mode and long-distance)

Question 15

What is vector transmission?

Answer 15

by saliva/feces from an insect/arthropod/animal

Question 16

What is a nosocomial infection?

Answer 16

An infection that occurs in a healthcare setting when the first stage of immune defenses is bypassed (barrier defenses)

Question 17

What is pathogenicity?

Answer 17

the ability to cause disease

Question 18

What is virulence?

Answer 18

the degree of ability to cause disease

Question 19

True or False:
Virulence factors are not essential for causing disease

Answer 19

False, they are essential for causing disease

Question 20

Can virulence be quantified?

Answer 20

Yes, depends on the # of microbes (“load”) ID50 and LD50

Question 21

What is ID50?

Answer 21

How many organisms it takes to infect half the population

Question 22

What is LD50?

Answer 22

The lethal dose- how many organisms it takes to kill half the population

Question 23

True or False:
The lower the number of ID50, the more virulent it is.

Answer 23

True

Question 24

What are cons of virulence factors?

Answer 24

-enables microbe to establish itself in host
-enhances microbes ability to cause disease

Question 25

What are pros of virulence factors?

Answer 25

-they are often antigenic -may be used serologically -may be inactivated by the immune system

Question 26

What are primary pathogens?

Answer 26

-they cause disease upon infection -NOT typically associated with host (ex: influenza)

Question 27

What are opportunistic pathogens?

Answer 27

-they cause disease under some circumstances -often members of normal flora (ex: e.coli)

Question 28

What are the important cocci gram-positive flora organisms?

Answer 28

-Staph aureus -Staph epidermis -Strep pyogenes -Viridians Strep

Question 29

What is the important spore forming bacilli gram positive flora organism?

Answer 29

Clostridium

Question 30

What is the important cocci gram negative flora organism?

Answer 30

Neisseria meningitidis

Question 31

What are the important bacilli gram negative flora organisms?

Answer 31

E. coli, Bacteroides, Pseudomonas, lactobacilli

Question 32

What is the important acid-fast flora organism?

Answer 32

mycobacterium

Question 33

What is the important fungi flora organism?

Answer 33

Candida albicans

Question 34

True or False: Flora organisms defend you, but some of them could be opportunistic pathogens

Answer 34

True

Question 35

True or False: Disease from opportunistic infections is common in immunocompetent persons

Answer 35

False- it is uncommon in immunocompetent persons

Question 36

How can opportunistic infection be promoted?

Answer 36

-Immunodeficiency or Immunosuppression -Flora microbes being "out of place" -Disturbance of "normal flora balance"

Question 37

Internal tissues, organs, and body fluids should be what?

Answer 37

Free of ALL microbes (sterile)

Question 38

What are the transmissions to a Portal of Entry?

Answer 38

-Respiratory Tract (RT) membranes -Gastrointestinal tract (GIT) membranes -Genitalurinary tract (GUT) membranes -Skin (Paraenteral) *Both vertical and Horizontal transmission are appropriate*

Question 39

What is the first step to colonization?

Answer 39

Attachment by... -Pili -Virus spikes -Capsules -Teichoic acids -Surface proteins

Question 40

What does attachment do in colonization?

Answer 40

The specificity determines the host range

Question 41

What does neutralization do?

Answer 41

Neutralizing antibodies can stop attachment

Question 42

What is colonization?

Answer 42

-Multiplication and Maintenance -Primary pathogens are "not in place"

Question 43

What are barriers to colonization?

Answer 43

-Competition with the normal flora (will defend you to some extent- has squatter rights to some parts of your body) -Barriers' defenses: -bile, stomach acid, skin secretion, competition for iron, etc

Question 44

After initial colonization, how do you avoid phagocytosis?

Answer 44

by capsules

Question 45

After initial colonization, how do you avoid antibodies?

Answer 45

-antigenic variation -acquiring an intracellular lifestyle

Question 46

What do enzymes that degrade tissue, antibodies, etc do?

Answer 46

Promote further invasion into tissues *NOT TOXINS*

Question 47

How is reduced phagocytosis reached?

Answer 47

Capsule production on surface of bacteria reduces "exposure" to complement proteins

Question 48

What can antigenic variation be due to?

Answer 48

-many antigen variants in a population -change of surface antigens over time

Question 49

What are the outcomes of antigenic variation?

Answer 49

-Immune system evasion -Possible re-infection (ex: flu, covid)

Question 50

What is the result of avoiding antibodies?

Answer 50

reduced exposure to the humoral immune response

Question 51

True or False: In avoiding antibodies, some intracellular microbes survive within phagocytes, other cells.

Answer 51

True

Question 52

What are exotoxins?

Answer 52

-external -secreted proteins -mostly gram positive -VERY potent -Cytotoxic and tissue specific -Soluble -Strongly antigenic -protective antibodies = neutralization

Question 53

What does heat labile mean?

Answer 53

can make toxoids

Question 54

True or False: Exotoxins are not heat labile

Answer 54

False, exotoxins are heat labile

Question 55

What are two problems presented with exotoxins?

Answer 55

You have an infection occurring, and you have exotoxin affects occurring that have to be treated simultaneously

Question 56

Where are the exotoxin genes encoded?

Answer 56

plasmid or phage-encoded

Question 57

What is a super-antigen?

Answer 57

an exotoxin that... -bind to MHC 11 proteins and presented without antigen processing -leads to polyclonal T cell stimulation -excess inflammatory cytokines

Question 58

What do excess inflammatory cytokines look like?

Answer 58

Low BP -> shock -> multi-organ failure (Toxic Shock Syndrome)

Question 59

True or False: The immune system must be highly regulated

Answer 59

True

Question 60

What do T-helper cells do?

Answer 60

express cytokines that are pro-inflammatory

Question 61

What are endotoxins?

Answer 61

-LPS -Gram negative -not a protein and not secreted -highly antigenic -LPS is heat-stable

Question 62

What are the two problematic components of LPS?

Answer 62

-Lipid A: toxic in bloodstream/membrane -O antigen (polysaccharide) is antigenic

Question 63

What does Lipid A do?

Answer 63

-prompts macrophages (immune cell stimulation) to express pro-inflammatory cytokines -induces fever and shock -Widespread coagulation

Question 64

True or false: Endotoxin genes are bacterial

Answer 64

False, endotoxin genes are chromosomal

Question 65

True or False: Endotoxins can't be denatured

Answer 65

True

Question 66

Infection may lead to....

Answer 66

shock

Question 67

How can infection lead to shock?

Answer 67

Decreased perfusion of blood -> decreased tissue oxygen -> multiple organ failure