Unit 1 - Determinants of Pathogenicity Flashcards
(173 cards)
1
Q
Define Pathogen
A
Organisms that cause disease in their host
2
Q
What are 4 examples of pathogens?
A
- Multicellular parasites
- Single celled parasites
- Bacteria
- Viruses
3
Q
True or False:
We rely on microbes to protect us everyday
A
True
- they create a biofilm on our skin
4
Q
Define vertical transmission
A
Transmission of infectious disease from mother to embryo, fetus or baby during pregnancy or childbirth
5
Q
Define horizontal transmission
A
Transmission of infectious disease after birth or from another source
6
Q
True or False:
Transmission of infectious disease can be by direct contact or indirect
A
True
7
Q
What is a vehicle?
A
A NON-living medium that can spread disease (water)
8
Q
What is a vector?
A
A LIVING medium that can spread disease (mosquito)
9
Q
True or False:
Vectors TEND to be indirect transmission
Vehicles TEND to be direct transmission
A
False
- Vectors tend to be direct
- Vehicles tend to be indirect
10
Q
True or False:
Animal feces are vehicles, not vectors
A
True
- this is b/c animal feces are not living things
- they are an animal product
11
Q
True or False:
The uterus is always germ-free
A
False
- uterus is germ-free until birth
12
Q
What protects the uterus from vaginal microbes?
A
Fetal membrane
13
Q
When does a baby first come into contact with microbes?
A
During delivery
14
Q
When does colonization (of microbes) of a baby occur?
A
Within 8 - 12 hours after birth
15
Q
What bacteria is contained within mother’s milk (when breastfeeding)?
A
Bifidobacterium (primarily)
- this bacteria has adapted along with us
16
Q
True or False:
Bottle fed babies are exposed to more bacteria in bottled milk compared to breast fed babies in mother’s milk
A
True
- bottle fed = coliforms, lactobacilli, enteric streptococci, staphylococci
- breast fed = bifidobacterium
17
Q
What percentage of microbes make up the human body?
A
90%
18
Q
Define niche
A
A compartment with unique properties
temperature, pH, nutrients, etc
19
Q
What are some examples of tissues that harbour resident microbes?
A
- skin
- upper respiratory tract
- GI tract
- vagina
- Urethra (outer opening only)
- External ear and canal
20
Q
What are some example of tissues/organs that are germ-free?
A
- Brain
- Muscles
- Blood
- Lower respiratory tract
- Kidneys and bladder
- Bones
- Ovaries/testes
21
Q
What is mutualism?
A
Two organisms cooperate to BOTH benefit
22
Q
What is commensalim?
A
One organism benefits WITHOUT harm to the other
23
Q
What is parasitism?
A
One organism benefits WHILE harming the other (or at the expense of)
24
Q
What is a reservoir?
A
The source of the disease/pathogen
- where the disease comes from or where the disease is hiding
25
Why do we NOT want everything to be sterile?
Because if we get exposed to bacteria/pathogens
- we won't have "good" bacteria to protect us
- not all microbes are bad
26
What must pathogens do first before they can infect an individual?
Adhere
| - attach to the host
27
True or False:
| Communal microbes have adapted to penetrate follicular canals on the skin
True
28
True or False:
| After hand washing communal microbes will grow back
True
| - because they have adapted to living in the follicular canals on the skin
29
What happens to communal microbes on the skin if you use anti-microbial soaps or alcohols?
They are all killed
| - you then leave it up to chance with what you are colonized with next (whatever is in the environment)
30
Why is the epidermis part of the immune system?
Because it acts as a barrier
| - skin is constantly falling off, and taking pathogens with it
31
Where do transient (temporary) microbes reside?
Colonize on the epidermis (surface)
32
Where do resident microbes reside (in relation to the skin)?
Penetrate into the deeper layers of the epidermis
33
What does it mean for microbes to be endogenous?
They are "within" the body
34
What does it mean for microbes to be exogenous?
They are "from an outside source"
35
What do sight, respiration, digestions, glandular secretion, birth, and urination - all have in common?
All require temporary exposure of internal tissues
36
Despite the hostile condition of the GI tract, why is it commonly colonized with microbes?
It is RICH in nutrients!
37
Approximately how many species makes up the biofilm of the mouth?
More than 600 bacterial species
38
What percentage of fecal volume do microbes make up?
Approx 10 - 30% volume
39
What does information the coliform count tell us?
Indicator of unsanitary conditions
40
Which bacteria in the large intestine provide vitamins to us?
E. coli
| - they ferment waste and produce B12 and Thiamine
41
True or False:
| The upper respiratory tract is germ-free
False
- the upper resp is rich in microbes
- the lower resp is germ-free
42
What is the suspected function of the tonsils and the appendix?
Sites where microbes are cultured
| - grown on purpose and released when necessary
43
Describe what microbial antagonism is
Resident microbes protect against other potentially harmful pathogens
44
What is the female vagina usually inhabited with and why?
Lactobacillus
- when they eat the glycogen produced by the estrogen, it produces an acidic environment (pH 4.5) that prevents the growth of other microbes
45
What happens to the Lactobacillus in the female vagina if the patient takes a broad spectrum antibiotic?
Kills off good and bad bacteria
46
True or False:
| Humans have been infected by retroviruses throughout our evolution
True
47
What is a distinctive feature of retroviruses?
Have the ability to integrate their DNA INTO the human (or other) genome
- virus DNA becomes part of the human genome
48
What happens to retroviruses once they integrate into your genome?
They become attenuated (less pathogenic)
| - b/c they don't want to kill you, they want the host alive
49
What retrovirus makes up 8 - 10% of the human genome?
HERV
| - human endogenous retrovirus
50
Define biofilm
Multiple species of microbes grow together and cooperate
51
Define microbial antagonism
Good bacteria impairing the colonization of pathogens
52
What are probiotics?
Commensal organisms believed to support human health
53
What do broad-spectrum antibiotics do?
Kill off "good" and "bad" microbes
54
How do exogenous microbes enter the body?
Through portals of entry
55
Define infection
Invasion of microbes into germ-free tissue
56
What is the virulence factor?
A characteristic of a microbe that increases its capacity to cause HARM
57
What are the 7 steps of the infection process?
1. Portal of entry
2. Adhesion
3. Invasion
4. Multiplication
5. Infection of target
6. Disease
7. Portal of exit
58
What does it mean if a pathogen has "infectivity" characteristics?
Capacity to invade and replicate in host tissue
59
If a microbe is pathogenic, how could you describe its virulence?
A quantitative measure of the pathology that results from infection
60
What is the infectious dose (ID)?
Minimum number of microbes to cause infection (morbidity)
61
What is the lethal dose (LD)?
Minimum number of microbes to cause death (mortality)
62
True or False:
| A toxin can cause infection
False
| - a toxin can be lethal, but they do not infect you
63
Define prevalence
Number of people in a population that are infected
64
Define incidence
Number of new cases (new infections) in a population
65
What does ID50 mean?
Minimum number of microbes to cause infection in 50% of the population
66
What does LD50 mean?
Minimum number of microbes to cause death in 50% of the population
67
True or False:
| A microbe with a HIGH LD is more deadly than a microbe with a LOW LD
False
- a high LD means that you need a large number of the microbe in order to cause death
- a low LD means that you need very few microbes in order to cause death
68
Where is E. coli typically found?
In the lower intestine of warm-blooded animals
| - produces toxins that break down the gut lining
69
Where is Vibrio Cholera found and what does it do?
Found in the small intestine of people and some aquatic habitats
- produces cholera toxin: draws salts and water into the intestion
- results in severe diarrhea
70
Should we be more concerned if a microbe has a HIGH ID50 and a HIGH LD50 ... or a LOW ID50 and a LOW LD50?
LOW
| - requires SMALL numbers in order to infect or kill
71
What does it mean if a pathogen is a "true" pathogen?
They can cause disease in individuals with a NORMAL functioning immune system
72
What does it mean if a pathogen is an "opportunistic" pathogen?
They only cause disease in immuno-compromised individuals
73
True or False:
| E. coli are typically high infectious but have a low-moderate virulence
True
- ID50 = 10
- low to moderate virulence depending on the strain
74
True or False:
| Vibrio cholera are typically highly infections and highly virulent
False
- poorly infectious (ID50 = 10^6 - 10^11
- but highly virulent!
75
What are three things that a pathogen must do in order to be virulent?
1. Adhesion
2. Invade - invade germ-free tissues/organs
3. Immune evasion - overcome the immune system
76
What are some adapted measures that multicellular parasites have adapted to assist with adhesion (3)?
1. Suckers
2. Hooks
3. Barbs
77
The head of a tapeworm has a crown of hooks, followed by a row of suckers to adhere to host's tissues. Is this a specific or non-specific adhesion method?
Non-specific
78
True or False:
| Tapeworms do not have their own digestive system
True
| - they absorb nutrients from you!
79
What can the falgellum be used for, and is it specific or non-specific?
1. Motility
2. Adherence
- Non-specific
80
What can fimbriae be used for, and are they specific or non-specific?
1. Motility
2. Adherence
- Non-specific
81
What is a slime layer used for and is it specific or non-specific?
1. Adherence
| - Non-specific
82
Do gram (+) or gram (-) bacteria have a cell wall?
Gram (+)!
83
What is the primary component of the cell wall of gram (+) bacteria?
Peptidoglycan
| thick layer
84
What is the main component on the outside of a gram (-) bacteria?
Lipopolysaccharide
| - with a thin layer of peptidoglycan
85
What is the name of the layer of polysaccharide that can be sticky or form a protective coat around a bacteria?
Capsule
| - has a sticky, sugary coating (non-specific)
86
What are the two main components of a virus?
1. Capsid
| 2. Envelope
87
What is the role of the capsid in a virus?
It is the inner core where genetic material is contained (DNA or RNA)
88
What is the role of the envelope in a virus?
It is the outer membrane where specific virus proteins bind to very specific host proteins
89
What is the name of the viral protein on the outside of HIV that binds to the surface of human cells?
GP120
90
What is the relevance of HIV and influenza having RNA genome?
RNA mutates faster than DNA genomes
| - easier for mutations to occur
91
What three non-specific features do multicellular parasites use for adhesion?
1. Hooks
2. Suckers
3. Barbs
92
What three non-specific features do bacteria use for adhesion?
1. Fimbriae
2. Flagella
3. Capsule
93
What two specific features do viruses use for adhesion?
1. Envelope
| 2. Capsid
94
What are the three methods that pathogens can used to invade germ-free tissues?
1. Exoenzymes
2. Toxins
3. Surviving endocytosis
95
True or False:
The human respiratory and digestive systems are vulnerable to invasion because the tissues are thin and in close proximity to the bloodstream
True
96
If fungi do not have a digestive system, how do they feed?
Secrete enzymes into the environment
| - then absorb those nutrients
97
What are exoenzymes?
Enzymes that are secreted out of the cell
98
What is hyaluronidase?
A "spreading factor"
- breaks apart the "cement" that is holding your cells together
- your cells will fall apart from each other - resulting in open wounds
99
What does the suffix "-ase" indicate?
An exoenzyme
100
What does mucinase do?
Disrupts the protective mucous membranes
| - an exoenzyme
101
What does keratinase do?
Digests structural proteins of skin and hair
| - an exoenzyme
102
What does collagenase do?
Digests connective tissue
| - an exoenzyme
103
What does hyaluronidase do?
Digests hyaluronic acid (cement that holds cells together)
| - an exoenzyme
104
What does coagulase do?
Promotes blood clotting
| - an exoenzyme
105
Why would some fungi have adapted to forming blood clots around them using coagulase?
If the fungi are surrounded by blood clots, the immune system won't be able to find them
106
What kind of toxins are typically used in invasion?
Exotoxins
| - used to kill any cells that are acting as a barrier
107
What do E. coli produce that kill gut epithelia?
Shiga toxin (verotoxin)
108
How have Salmonella enterica adapted to invade tissues?
Surviving Endocytosis
1. Adhesion by fimbriae
2. Secretion system (injects proteins into cells, reprogram them, tell them to eat Salmonella)
3. Salmonella do not get eaten by lysosomes
4. Multiply internally
5. Released into bloodstream in large numbers
109
What are 4 things that pathogens would have to evade in order to survive the immune system?
1. Tissue barriers (physical barriers)
2. Gastric juices (physiological barrier)
3. Anti-phagocytic factors
3. Leukocytes
110
What is the name of the microbe that lives in the stomach of approx. 50% of people?
Helicobacter pylori (H. pylori)
111
How have H. pylori adapted to living in the stomach of people (2)?
1. Corkscrew motion of flagella drills the microbe through mucosal lining of the stomach
2. Produces urease enzyme which degrades urea into ammonia ... this neutralizes the stomach acid
112
How can a microbe survive phagocytosis (2)?
1. By creating a capsule to surround it
| 2. Hiding inside host cells
113
What are leucocidins?
Toxins secreted by some microbes that specifically kill immune cells
- it is a protein
114
What is the resulting effect of leucocidins?
Will immuno-compromised the host
115
What are two examples of microbes that secrete leucocidins?
1. M. tuberculosis
| 2. HIV
116
What does the suffix "-in" tell you?
It is a PROTEIN!
117
What are the two classes of toxins?
1. Endotoxin
| 2. Exotoxin
118
What kind of bacteria produces endotoxins?
Produced by gram (-) bacteria
| - from degradation of lipopolysaccharide cell wall
119
When are endotoxins fatal?
Only fatal in LARGE doses
| - can induce fever that can lead to death
120
What kind of bacteria produces exotoxins?
Produced by gram (-) OR gram (+) bacteria!
121
True or False:
| Exotoxins are proteins
True
122
When are exotoxins fatal?
In SMALL doses
| - can lead to tissue or organ failure
123
```
True or False:
A gram (+) bacteria can produce endotoxins and exotoxins
```
False!
| - A gram (-) bacteria can produce endotoxins and/or exotoxins
124
True or False:
| If you heat up an endotoxin, it will degrade
False
- Endotoxins are stable at high temperatures b/c they are lipids
- therefore, still toxic when heated
125
True of False:
| Endotoxins cannot be converted to toxoids
True
| - antibodies do not bind to lipids well - therefore there is NO ANTI-TOXIN
126
What is the main clinical concern when dealing with endotoxins?
Managing the escalation of the inflammatory response
127
What is a toxoid?
A modified toxin
- it keeps its general shape, but it is not as harmful
- we can make antibodies against them
128
True or False:
| Exotoxins denature at high temperatures
True
129
True or False:
| Anti-toxins cannot be produced for exotoxins
False
130
True or False:
| Exotoxins are the result of the degradation of the lipopolysaccharide cell wall
False
| - Exotoxins are secreted from LIVE cells
131
True or False:
| Endotoxins can cause damage if the cells are alive or dead
True
| - this is because the toxins are released from the degradation of the LPS
132
What is an example of a Receptor Ligand Exotoxin?
AB toxin
- Pertussis
- Cholera
- Shiga
133
What are two domains of the AB toxin and what do they do?
A domain = an enzyme that disrupts the cell function
| B domain = binds to a specific receptor on the target cell surface
134
True or False:
| AB toxins enter the target cell via endocytosis
True
135
What happens to the AB toxin once it enters the target cell?
Lysosomes break up the AB linkages
- A domain gets released into the body and causes harm
- (acidification of vacuole dissociates th A enzyme)
136
True or False:
| Endotoxins can be deactivated and then injected into a host to make antibodies
False
| - EXOTOXINS can be deactivated and then injected into a host to make antibodies
137
What happens when a patient is injected with a toxoid?
Patient becomes immune to the toxin
| - these are exotoxins
138
What happens when a patient is injected with an anti-toxin?
Rapid relief to a NON-IMMUNE patient
- immunity is NOT transferred
- these are exotoxins
139
What are two examples of exotoxins that affect the GI tract? What is their proper name and what do they do?
Enterotoxins
1. Shiga toxin = E. coli degrades the GI wall = blood diarrhea
2. Choleragen (produced by Vibrio cholera) - stimulates water secretion into gut = rice-water stool
140
What is the botulism toxin an example of and what does it do?
Botulism toxin = Neurotoxin
| - causes flaccid paralysis (numbness)
141
What is tetanus an example of and what does it do?
Tetanus = Neurotoxin
| - causes spastic paralysis (constant muscle contraction)
142
What is the name of the exotoxin that affects red blood cells? What does it do?
Hemolysins
- S. pyogenes
- breaks open RBCs
143
What is the name of the exotoxin that affects white blood cells? What does it do?
Leucocidins
- S. aureus (necrotizing pneumonia)
- Targets WBCs and destroys them
144
Which has a lower LD50, endotoxins or exotoxins?
Exotoxins
| - you only need a small amount to kill someone
145
True or False:
| Exotoxins are proteins
True
146
What are 4 types of exotoxins?
1. Enterotoxin = GI
2. Neurotoxin = neurons
3. Hemolysin = RBCs
4. Leucocydin = WBCs
147
What is the role of hemoproteins in humans?
Helps iron dissolve by associating it with proteins called hemoproteins
- ferratin, transferrin, lactoferrin
148
True or False:
| Bacteria, fungi and other microbes have easy access to iron
False
- they are often starved for iron
- therefore, adapted proteins that bind iron at HIGH AFFINITY
149
What is affinity?
The strength at which two molecules bind
150
What are siderophores and what do they do?
High-affinity proteins that absorb heme and iron
| - to be taken back into the cell
151
What microbes secretes siderophores?
Bacteria
| - TB, E. coli, Anthrax, Cholera, Black Plague
152
What is the suffix that indicates a siderophore?
"-bactin"
153
In the body, what are a rich source of iron?
RBCs
154
What can microbes produce that disrupt RBCs in order to access their iron content?
Hemolysin
155
What is one method of classifying Streptococcus species?
By their hemolysis patterns
156
What is the important difference that a chocolate agar and a blood agar plate will tell you?
1. If it grows on chocolate, it likes iron but cannot lyse RBCs
2. If it grows on blood agar, it likes irons AND can lyse RBCs
157
What does the alpha pattern tell you?
Partial lysis of RBCs
| - ex: S. pneumoniae
158
What does the beta pattern tell you?
Complete lysis of RBCs
| - ex: S. pyogenes
159
What does the gamma pattern tell you?
Non-hemolytic
| - non-pathogenic commensals
160
True or False:
| Humans bind iron to siderophores while bacteria bind iron to hemoproteins
False
- Humans bind iron to hemoproteins
- Bacteria bind iron to siderophores
161
True or False:
| Mechanisms involved in evolution and adaptation are considered virulence factors for microbial populations
True
162
The immune system uses what two key antigens to identify and develop immunity against influenza?
1. Hemagglutinin (HA)
| 2. Neuraminidase (NA)
163
What does the virus do if the immune system detects a specific HA antigen shape?
The virus mutates to change it's shape
164
What is "antigenic drift"?
Small changes/variations
- DUE TO MUTATION
- changes are small enough that it will cause symptoms but your immune system will recognize the virus
165
What is "antigenic shift"?
Major changes
- DUE TO GENETIC REASSORTMENT
- so much so, that your immune system does not recognize it as the flu (example)
- immune system does not formulate a response
166
True or False:
| Avian flus rarely infect humans. But avian and human influenza can infect pigs
True
167
What happens TO THE VIRUS if a pig is infected with both avian and human influenza?
The virus reshuffles its RNA molecules
- to form a virus that is dramatically different
- we would not have immunity to it
168
What is genetic reassortment?
When a virus reshuffles it's RNA (or other genetic molecules)
- ex: avian and human flu in pigs = new flu virus
169
What does antigenic drift usually cause?
A disease outbreak
| - a disease that occurs at greater frequency
170
What does antigenic shift usually cause?
A pandemic
| - humans have no natural immunity and the disease quickly spreads throughout the world
171
What is the african sleeping sickness caused by?
Protest parasite called a TRYPANOSOME
172
Why is it so hard for the immune system to beat the african sleeping sickness?
It has VARIABLE surface glycoproteins
- once the immune system develops resistance
- the pathogen changes shape to evade the immune cells
173
What is antigenic variation?
Changes in cell surface features to evade immune cells
