Exam 4 Ch 18

Question 1

Zoonotic transfer

Answer 1

Spread of a infectious agent from its natural animal host to a human

Question 2

vector-borne transmission

Answer 2

Spread of an infectious agent from an infected individual to another organism such as an insect that then transmits the infectious agent to a different susceptible host

Question 3

reservoir host

Answer 3

Natural host that supports replication of a pathogen

Question 4

Epidimieology

Answer 4

study of patterns of disease within populations

Question 5

morbidity rate

Answer 5

Rate of disease

Question 6

mortality rate

Answer 6

Rate of death associated with disease

Question 7

incidence

Answer 7

Number of new cases of a disease appearing in a population during a specific time period

Question 8

prevalence

Answer 8

Total number of cases of a disease in a population at a particular time or during a particular time period

Question 9

endemic disease

Answer 9

Disease that is normally present in a population

Question 10

epidemic

Answer 10

Significant rise in incidence of a disease above that normally expected in a population

Question 11

Outbreak

Answer 11

Cluster of cases appearing within a short period of time in a localized population

Question 12

pandemic

Answer 12

Global epidemic, usually on more than one continent

Question 13

primary pathogen

Answer 13

Microbe that causes disease in otherwise healthy hosts

Question 14

opportunistic pathogen

Answer 14

Microbe that causes disease only when a host has been compromised

Question 15

virulence

Answer 15

Degree of severity of disease a pathogen is capable of causing

Question 16

Pathogenecity

Answer 16

Relative measurement of the ability of a microbe to cause disease

Question 17

Virulence vs pathogenicity

Answer 17

Virulence describes directly how harmful a pathogen (SEVERITY) it is. Pathogenicity describes the overall process of infection such as transmission (ABILITY TO INFECT)

Question 18

Case-to-infection (CI) ratio

Answer 18

The proportion of infected individuals who develop the disease. Used to measure pathogenicity

Question 19

pathogenesis

Answer 19

Process by which a pathogen causes disease

Question 20

symptom

Answer 20

Subjective disease state, such as muscle aches

Question 21

sign

Answer 21

Objective disease state that can be readily observed or measured, such as a rash or fever

Question 22

symptom vs sign

Answer 22

symptom is subjective and sign is objective

Question 23

virulence factor

Answer 23

Product made by a pathogen that enhances its ability to cause disease

Question 24

antigenic variation

Answer 24

Change in molecules on the surface of a pathogen to which the immune system responds; can allow pathogen to avoid immune detection

Question 25

latent infection

Answer 25

Infection characterized by a delay or cessation of disease; in viral disease, characterized by limited transcription of the viral genome; results in reduced immune response; see also latency

Question 26

autophagy

Answer 26

Intracellular degradation in which materials to be destroyed are encased in a membrane and sent to the lysosome

Question 27

toxin

Answer 27

Substance of biological origin that damages a host

Question 28

apoptosis

Answer 28

Cell death accomplished through a highly ordered and tightly controlled cascade of chemical-signaling events within the cell that results in its destruction without the release of damaging cell constituents or triggering of inflammation

Question 29

necrosis

Answer 29

Cell death that occurs through chemical or physical cell injury or loss of oxygen supply; results in cell rupture and the release of toxic cellular contents and cytokines to the surrounding tissues, producing further cell death and triggering inflammation

Question 30

fomite

Answer 30

Inanimate object via which pathogens may be transferred to a susceptible host aka water or food

Question 31

Indirect trasmission

Answer 31

Spread of an infectious agent from one individual to another via an object, like a contaminated inanimate object, water, food, or an insect

Question 32

Direct transmission

Answer 32

Spread of an infectious agent via physical contact between an infected individual and a susceptible individual

Question 33

Koch’s postulates

Answer 33

Guideline for demonstrating that a specific microbe causes a specific disease:

1. The suspected microbe should exist in every individual with the disease and account for the signs and symptoms of the disease.
2. The microbe should not be fortuitously associated with other diseases as a non-pathogen.
3. After being isolated and grown in a pure culture, the microbe should cause the same disease following inoculation of a healthy host.

A fourth postulate, stating that the suspected microbe then should be re-isolated from an experimentally inoculated host, often has been added to this original list.

Question 34

Molecular Koch’s postulates

Answer 34

Guideline using molecular tools to demonstrate that a specific microbial product is a virulence factor:

• The virulence factor gene should be present and expressed in pathogenic strains of the microbe.
• Experimental inactivation of the virulence factor gene should lead to a decrease in virulence.
• Experimental reversion of this inactivating change should result in a restoration of virulence.
• The virulence factor gene should be expressed during an infection.
  Resistance to the virulence factor must provide protection.

Question 35

prevalence vs incidence

Answer 35

prevalence is the total number of cases over a period of time or at a specific time. Incidence is the number of new cases over a period of time.

Ex:
There were 500 cases of the flu during November. 400 started in November. The 500 cases are the prevalence, and the 400 new ones are the incidence.

Question 36

horizontal trasmission

Answer 36

Spread of an infectious agent between members of a species that are not parent and offspring

Question 37

vertical trasnmission

Answer 37

Spread of an infectious agent from parent to child

Question 38

pathogenic islands and their role in making new pathogenic microbes through horizontal gene transfer

Answer 38

Region of a chromosome containing multiple virulence factor genes. They are sometimes transferred to non-pathogenic bacteria creating new pathogens

Question 39

Be familiar with horizontal gene transfer mechanisms: transduction, transformation,
conjugation.

Answer 39

Transduction: the process by which DNA is transferred from one bacterium to another by a virus.

Transformation: a process where bacteria can uptake foreign extra-cellular DNA

conjugation: DNA is transferred from a donor to a recipient bacterium by direct contact

Question 40

Steps of a microbe causing disease

Answer 40

1. Gain entry into host
2. Attach to target organism/cells
3. Evade host defenses
4. Obtain nutrients from the host
5. Exit the host

Question 41

How does attachment occur

Answer 41

Most commonly through protein-to-protein interactions: viruses tend to bind to specific host cell receptors
Less commonly attachment occurs through generalized interactions: rice blast fungus attaching to hydrophobic surfaces like cells

Question 42

How do microbes evade host defenses

Answer 42

Antigenic variation, latency, capsules, phage evasion, or phage defense

Question 43

exotoxins

Answer 43

produced by bacteria that cause immune responses

Question 44

endotoxins

Answer 44

part of the microbial itself