Transmission of infectious disease

Question 1

host-microbe interactions

Answer 1

• dynamic give and take between host and microbes
• can range from benign to serious causing disease

Question 2

human microbiota

Answer 2

• mutualistic relationship
• the microbial population associated with the human body
• human provides nutrients
• promotes immune system maturation
• role of opportunistic pathogens; compete with bad pathogens for real estate; keep in check

Question 3

tropism

Answer 3

preference for a specific host or tissue

Question 4

dysbiosis

Answer 4

• disruption of microbiota
• ex. antibiotics can kill good bacteria as well

Question 5

pathogenicity

Answer 5

ability of a microbe to cause disease

Question 6

virulence

Answer 6

degree of extent of disease that a pathogen causes

Question 7

virulence factors

Answer 7

ways pathogens overcome host defenses

Question 8

ways to invade the immune system:

Answer 8

• toxins
• adhesion factors
• nutrient acquisition
• invasion strategies

Question 9

attenuated

Answer 9

pathogen is still infectious but does not cause disease
- different for immunocompromised hosts
- attenuation is advantageous because virulence factors use energy to produce

Question 10

infectious dose (ID50)

Answer 10

the number of bacterial cells or viral particles needed ti establish an infection in 50% of susceptible hosts

Question 11

lethal dose (LD50)

Answer 11

the amount of toxin needed to kill 50% of untreated affected hosts

Question 12

toxins

Answer 12

• molecules that generate adverse host effects in a low concentration
• can be tougher to destroy than the originating organism

Question 13

toxigenic organisms

Answer 13

organisms that produce/generate toxins

Question 14

toxemia

Answer 14

toxin in bloodstream

Question 15

endotoxin

Answer 15

• released by gram negative bacteria when the cell is destroyed
• can lead to septic shock and death
• not readily neutralized
• no effective vaccines or therapies

Question 16

exotoxins

Answer 16

• toxic soluble proteins made by gram negative and gram positive bacteria
• released by the cell into the envrionment

Question 17

type 1 exotoxins

Answer 17

• membrane acting
• dont enter the host cells

Question 18

type 2 exotoxins

Answer 18

• damage host membranes
• creates holes in membranes that causes cell to leak and die

Question 19

type 3 exotoxins

Answer 19

• intracellular AB toxins
• binding portion B binds to plasma membrane
• toxin enters cell by endocytosis
• active portion A enters the host cell and exerts an effect

Question 20

five steps to infection

Answer 20

1. pathogen enters host
2. pathogen adheres to host tissues
3. pathogen must invade tissues and obtain nutrients
4. pathogen must evade host immune defenses in order to replicate
5. pathogen must be transmitted to a new host

Question 21

portal of entry

Answer 21

anywhere you have an opening to the environment; a potential route of infection

Question 22

adhesins

Answer 22

• allow pathogen to stick to surface of host cells (specifically or nonspecifically)
• make ideal vaccine targets

Question 23

biofilms

Answer 23

• bacteria growing as a community on a surface
• 60-80% of human infections originate from them
• from implanted devices
• ex. dental plaques
• often change in virulence factor expression

Question 24

quorum sensing

Answer 24

biofilms are able to communicate via molecular signals that help them become more virulent; can have an adverse reaction to the host

Question 25

invasins

Answer 25

- allow pathogens to invade host tissues by breaking cell junctions or altering host cytoskeleton - often have a motility feature

Question 26

how to pathogen obtain nutrients

Answer 26

siderophores

Question 27

what are siderophores

Answer 27

iron binding complexes that find a human "lock-box" of iron and steal it for the bacterial cell for food and growth

Question 28

cytopathic effect

Answer 28

damage or kill host cells; not the cause of all damage

Question 29

how may pathogens hide from host defenses

Answer 29

- there may be intracellular pathogens - latency (ability to survive inside a host) - antigen masking, mimicry, variation

Question 30

antigen masking

Answer 30

pathogen covers itself in host factors to avoid immune detection

Question 31

antigen mimicry

Answer 31

pathogens antigens resemble host molecules, helping it evade immune responses

Question 32

antigen variation

Answer 32

pathogen switches its antigens, thwarting the mounting immune response

Question 33

how may a pathogen undermine a host immune system

Answer 33

- interfere with phagocytosis - immune suppression

Question 34

ways to interfere with phagocytosis

Answer 34

- releasing toxins that kill phagocytes - avoiding phagocytosis with a capsule - blocking fusion of lysosome with phagosome - escaping phagosome and living in a phagocytic cell - adapting to harsh phagolysosome environment or neutralizing hydrolytic enzymes

Question 35

biosafety level (BSL)

Answer 35

categorized based on: level of infectivity, extent of disease caused and mortality rate, mode of transmission, availability of preventions/treatments for disease

Question 36

BSL 1 and 2

Answer 36

- well characterized - rarely causes disease in healthy people - human body tissues or fluids

Question 37

BSL 3

Answer 37

- serious or lethal human disease - often airborne, may be treatable

Question 38

BSL 4

Answer 38

- "exotic" pathogens - extremely dangerous

Question 39

universal precautions

Answer 39

guidelines applied when dealing with patients suspected or known to have bloodborne pathogen - originated with HIV epidemic

Question 40

standard precautions

Answer 40

all patients treated as potential source of bloodborne or other infectious agents