Wk 1 Infectious Agents

Question 1

Bacteria

Answer 1

can grow under appropriate conditions in the absence of a host.
* Some exceptions (i.e. Rickettsia is an obligate intracellular bacterium)

Question 2

Viruses

Answer 2

obligate intracellular parasites that must replicate inside cells, using cellular machinery.

Question 3

Fungi

Answer 3

non-motile filamentous, branching strands of connected cells: replicate as yeasts or molds.

Question 4

Parasite

Answer 4

Eukaryotic organism that lives on or in a host organism and gets its food from or at the expense of its host.
* Protozoa (unicellular)
* Helminths (tapeworms, hookworms, roundworms, etc.)
* Ectoparasites (ticks, mites, fleas, lice).

Question 5

Prion

Answer 5

“infectious proteins”
non-replicating

Question 6

Size comparison of microbes

Answer 6

Question 7

Symbiosis

Answer 7

2+ organisms living in close proximity
-usually mutually beneficial

Question 8

Pathogen

Answer 8

organism that usually lives as a symbiont, but under the right circumstances an organism that causes disease in its host

Question 9

Pathobiont

Answer 9

organism that becomes a pathogen under certain circumstances

Question 10

Commensal

Answer 10

an organism that benefits due to close proximity to its host, while the
host remains unaffected (one-sided symbiosis)

Question 11

Parasitism

Answer 11

one organism benefits from the relationship at the expense of the other

Question 12

Virulence

Answer 12

characteristics of an organism that influence its ability to cause disease (pathogenesis)

Question 13

Immunogenicity

Answer 13

the ability of an organism to induce an immune response in the host

Question 14

Sepsis

Answer 14

Acute illness caused by infectious agents and/or their products circulating in the bloodstream

Question 15

Bacteremia

Answer 15

bacteria circulating in bloodstream

Question 16

Viremia

Answer 16

viruses circulating in bloodstream

Question 17

Fungemia

Answer 17

fungi circulating in bloodstream

Question 18

parasitemia

Answer 18

parasites circulating in the bloodstream

Question 19

Successful pathogen features

Answer 19

• Gains access to the host (contamination)
• Adheres to the host (adherence)
• Replicates on host surfaces (colonization)
• Invades tissues (invasion)
• Produces toxins (damage)
• Eludes host immune responses (immune evasion)
• Propagates (replication)
• Sheds (transmission)
  *** The vast majority of microbes are not pathogens

Question 20

What is the chain of infection?

Answer 20

Question 21

How is bacterial nomenclature identified?

Answer 21

By genus and species

ie. staphylococcus aureus or Escherichia coli

• always italicized

Question 22

Bacterial infections classified by disease/location

Answer 22

Question 23

5 modes of direct transmission

Answer 23

• Skin to skin contact
• Droplet (short-range aerosol due to coughing, talking, etc.)
• Kissing
• Sexual contact
• Contact with soil or vegetation

Question 24

3 modes of indirect transmission

Answer 24

• Droplet (organisms carried in small droplets, dust, etc.)
• Vehicles: food, water, biologic products (i.e. blood), fomites (inanimate objects that can transfer disease)
• Vectors: mosquitoes, fleas, ticks, etc.

Question 25

5 routes of transmission

Answer 25

• Respiratory tract
• Fecal oral (GI pathogens)
• Skin
• Blood
• Mucous membranes

Question 26

The triad of infectious disease

Answer 26

Question 27

4 categories of antimicrobial therapy

Answer 27

• Antibiotics: against bacteria
• Antivirals: against viruses
• Antifungals: against fungi
• Antiparasitics: against parasites

Question 28

What are 4 modes of antimicrobial use?

Answer 28

• Prophylactic: used to prevent infection based on risk factors
• Empiric: used to treat based on experience and relevant information available when you do not know the pathogen causing disease
• Preemptive: used to prevent based on preliminary data anticipating an infection
• Definitive: used to treat and expect cure after etiology has been identified

Question 29

Bactericidal

Answer 29

cause death and disruption of the bacterial cell, include drugs that primarily act on the cell wall (i.e., beta-lactam antibiotics), cell membrane (i.e., daptomycin), or bacterial DNA (i.e., fluoroquinolones)

Question 30

Bacteriostatic

Answer 30

inhibit bacterial replication without killing the organism. Most bacteriostatic drugs, including sulfonamides, tetracyclines, and macrolides, act by inhibiting protein synthesis

Question 31

What is MIC?

Answer 31

= minimum inhibitory concentration
-lowest [] that prevents visible growth after 18-24h of incubation

Question 32

What is MBC?

Answer 32

= minimum bactericidal concentration
-lowest [] that totally suppresses growth or results in >99.9% decline in colony count after overnight incubation

Question 33

4 direct types of adverse events

Answer 33

• Allergy
• Toxicity
• Drug-drug interaction * Therapeutic failure

Question 34

Epidemiologic distribution of disease

Answer 34

Sporadic: normally absent, but can occur without predictability
Endemic: predictable regularity
Epidemic: greater frequency than expected Outbreak: mini-epidemic, restricted in time and place
Pandemic: globally spread large epidemic affecting several countries and/or continents

Question 35

Notifiable Diseases

Answer 35

Voluntary reporting to CDC by state for monitoring disease data
-list is modified annually by CDC

Question 36

Reportable Diseases

Answer 36

Mandatory reporting by state
-uses personal identifier
-each state has its own laws and regulations for defining list
-list varies among states and over time