Lecture 16 Host Microbe Interactions Flashcards
(268 cards)
1
Q
Ancients thought _______________ were divine punishment
A
diseases
2
Q
What are the “4 humors” from ancient times?
A
black bile, yellow bile, phlegm, blood
3
Q
What does bacillus anthracis cause?
A
anthrax
4
Q
What are Koch’s postulates?
A
criteria for establishing cause of disease
5
Q
Robert Koch offered evidence of what is now known as ……
A
germ theory of disease
6
Q
How do we contact numerous microorganisms daily?
A
breathe in, ingest with food and drink, pick up on skin
7
Q
Most swallowed microorganisms…..
A
die in stomach or are eliminated in the feces
8
Q
What are opportunistic pathogens?
A
Microbes that can cause disease if there is an opportunity
9
Q
What characterizes an immunocompromised individual?
A
Weakness or defects in immunity leave people vulnerable to invasion
10
Q
What factors are involved in making a person immunocompromised?
A
malnutrition, cancer, AIDS or other disease, surgery, wounds, genetic defects, alcohol or drug abuse, and immunosuppressive therapy
11
Q
What are some examples of symbiosis?
A
Mutualism, commensalism, parasitism
12
Q
What is mutualism?
A
both partners benefit
13
Q
What is commensalism?
A
one partner benefits, other is unharmed
14
Q
What is parasitism?
A
one organism benefits at expense of other
15
Q
Name examples of mutualism
A
in large intestine, some bacteria synthesize vitamin K and B vitamins, which host can absorb; bacteria are supplied with warmth, energy sources
16
Q
Name examples of commensalism
A
Many microbes living on skin neither harmful nor helpful, but obtain food and necessities from host
17
Q
Name examples of parasitism
A
All pathogens are parasites, but medical microbiologists often reserve for eukaryotic pathogens (for example, protozoa, helminths)
18
Q
What are normal microbiota?
A
microorganisms routinely
growing on a healthy body
19
Q
Resident microbiota inhabit sites for….
A
extended periods
20
Q
Normal microbiota or microbiome are important for….
A
human health
21
Q
What is metagenomics?
A
analysis of DNA used to study microbiota
22
Q
Breastfeeding affects _____________ of microbiome
A
composition
23
Q
Colonization begins at …..
A
birth
24
Q
Microbiome is different after __________ birth than after _________________ birth
A
vaginal, caesarian
25
more ________________ in obese individuals
Firmicutes
26
more ____________ in those that are thin
Bacteroides
27
Microbiota __________ with weight loss and diet due to influence of ____________
change, prebiotics
28
What is dysbiosis?
imbalance in the microbiome
29
Dysbiosis is related to some.....
disease states
30
Dysbiosis can be _______________ induced
antibiotic
31
Name three ways the human microbiome protects against pathogens.
*Covering of binding sites prevents attachment
* Consumption of available nutrients
* Production of compounds toxic to other bacteria
32
When microbiome is suppressed (for example during antibiotic treatment), pathogens may ______________________, causing ______________
colonize, disease
33
Some antibiotics inhibit _____________ which results in vulvovaginal candidiasis
Lactobacillus
34
In vagina of mature females, Lactobacillus suppresses growth of __________________
Candida albicans
35
Oral antibiotics can inhibit intestinal microbiota, which allows overgrowth of toxin-producing _______________________________
Clostridioides difficile
36
Antibodies against normal microbiota may also bind to __________________
pathogens
37
Adult immunity to __________________ thought largely to be cross-reactivity to pre-existing antibodies.
Heamophilus influenzae
38
Mice in microbe-free environment have underdeveloped.....
mucosal-associated lymphoid tissue (MALT)
39
Immune system lessens response to many microbes in _________________
gut
40
What is the hygiene hypothesis?
The proposal that insufficient exposure to microbes during childhood can lead to allergies and autoimmune diseases.
41
How do microbes aid in digestion?
They break down fibers and increase nutrients
42
What is colonization?
refers to microbe establishing itself and multiplying
43
The term infection is used for....
colonization of pathogen
44
What is a subclinical infection?
No symptoms or mild symptoms
45
Infectious disease prevents _______________ and damages ______________
normal function, host
46
What is the difference between infection and disease?
Infection is the first step, occurs when bacteria, viruses or othermicrobes that cause disease enter your body and begin to multiply.
Disease occurs when the cells in your body are damaged — as a result of the infection — and signs and symptoms of an illness
appear.
47
What are symptoms of disease?
subjective effects experienced by patient (pain,
nausea, malaise, headache, queasy feeling)
48
What are signs of disease?
objective evidence that can be observed/measured
(rash, pus formation, fever, swelling, vomiting, diarrhea, etc.)
49
The initial infection is the.....
primary infection
50
Damage can predispose individual to developing a ___________________
secondary infection
51
Name an example of a secondary infection taking place
Respiratory illness impairing mucociliary escalator
52
What is pathogenicity?
ability of a pathogen to cause disease
53
What is a primary pathogen?
microbe or virus that causes disease in otherwise
healthy individual
54
Name examples of primary pathogens
Diseases such as plague, malaria, measles, influenza, diphtheria, tetanus, tuberculosis are caused by primary pathogens
55
What is an opportunistic pathogen?
causes disease only when body’s immune defenses are compromised or when introduced into unusual location
56
Opportunistic pathogens can be....
members of normal microbiota or common in environment
(Pseudomonas)
57
virulence refers to...
degree of pathogenicity
58
Virulence factors are....
substances that allow microorganism to cause
disease (capsules, toxins, immune avoidance mechanisms, etc.)
59
______________ or _________________ diseases easily spread from one host to another
communicable or contagious
60
What is an infectious dose?
number of microbes necessary to establish infection
61
Shigellosis results from approximately ______________ Shigella
10 to 100
62
Salmonellosis results from as many as ______________ ingested Salmonells enteric serotype Enteritidis
10e6
63
Why are so many more salmonella needed to cause disease (as compared to shigellosis)
Difference largely reflects ability of Shigella to survive stomach acid as well as the relative sensitivity of Salmonella to the same
64
What is an infectious dose? (ID50)
50%: is number of cells required to infect
50% of the population of test animals (can be considered a
measure of virulence)
65
What is the incubation period?
time between infection (first exposure) and onset
66
What does the incubation period depend on?
growth's rate, host's condition, infectious dose
67
Does the incubation period vary?
Yes
68
What is illness defined as?
signs and symptoms of disease are prevalent
69
Illness may be preceded by....
prodromal phase (vague symptoms)
70
What is convalescence?
recuperation, recovery from disease
71
After recover (or vaccination), _______________ usually protect from reinfection with the same microbe
memory cells
72
Name the three steps of progression of infectious disease:
incubation period, illness, convalescence
73
What is an acute illness?
Illness is short term because the pathogen is eliminated by the host defenses; person is usually immune to reinfection.
74
What is a chronic illness?
illness persists over a long period of time
75
What is a latent illness?
illness may recur if immunity weakens
76
What is an acute infection and provide an example?
symptoms develop quickly, last a short period of time (strep throat)
77
What is a chronic infection and provide an example?
develop slowly, last for moths or years (tuberculosis)
78
What are latent infections?
never completely eliminated; microbe exists in host tissues without causing symptoms.
79
What are examples of latent infections?
chicken pox, tuberculosis, cold sores, genital herpes
80
Chickenpox results from _________________ virus; immune response _____________, but virus hides in ____________________, can later produce viral particles resulting in ________________-
varicella-zoster
stops
sensory nerves
shingles
81
Chicken pox is an example of __________ illness
acute
82
What is a localized infection?
microbe limited to a small area
83
What is an example of a localized infection?
boil caused by staphylococcus aureues
84
What is a systemic infection?
agent spread throughout body
85
What is an example of a systemic infection?
Lyme disease
86
What are bacteremia?
bacteria circulating in blood
87
Bacteremia are not necessarily a ___________________
disease state
88
How can bacteremia occur transiently?
following vigorous tooth brushing
89
Bacteremia may lead to a systemic inflammation called ______________
sepsis
90
What is toxemia?
toxins circulating in bloodstream
91
What is viremia?
viruses circulating in bloodstream
92
Koch's postulates provide....
foundation for establishing that a given microbe causes a specific infectious disease
93
According to Koch's postulate, microorganism must be present in.....
every case of disease
94
According to Koch's postulate, organism must be grown in....
pure culture from diseased host
95
According to Koch's postulate, same disease must be produced when pure culture is....
introduced into susceptible hosts
96
According to Koch's postulate, organisms must be recovered from....
be recovered from experimentally infected hosts
97
A limitation of Koch's postulates is that some organisms cannot be grown in ___________________, such as the causative agent of ________________.
laboratory medium
syphillis
98
Infected individuals do not always have _______________, some examples include.....
symptoms (cholera, polio, UTIs)
99
A limitation of Koch's postulates is that some diseases are.....
polymicrobial
100
What is an example of a polymicrobial disease?
periodontal disease
101
A limitation of Koch's postulates is that suitable animal hosts are not always.....
available for testing
102
A limitation of Koch's postulates is that humans may be only affected....
host species
103
What are examples of diseases in which humans are the only affected host species?
gonorrhea, syphilis, HIV
104
It is not ethical to test the _________________ on humans
postulates
105
What are molecular Koch's postulates?
A modern day recapitulation of Koch’s Postulates taking into account the limitations already addressed
106
______________________ or its product is identified in a pathogenic strains of organism
Virulence factor gene
107
Mutating gene in vitro to disrupt function should.....
reduce virulence
108
______________ or _______________ of gene should restore virulence
Reversion or replacement
109
What infectious diseases produce toxins that are ingested?
Clostridium botulinum, Staphylococcus aureus
110
What infectious diseases colonize mucous membranes and produce toxins?
Vibrio cholerae, E. coli O157:H7, Corynebacterium diphtheriae
111
What infectious diseases invade host tissues and avoid defenses?
Mycobacterium tuberculosis, Yersinia pestis, Salmonella enterica
112
What infectious diseases invade host tissues and produce toxins?
Shigella dysenteriae, Clostridium tetani
113
What are 4 general patterns of infectious diseases?
-produce toxins that are ingested
-colonize mucous membranes and produce toxins
-invade host tissues and avoid defenses
-invade host tissues and produce toxins
114
A successful pathogen needs to ___________________ only long enough to multiply and exist
overcome host defenses
115
Pathogen that overwhelms the host may....
kill it and lose nutrients and opportunity for transmisison
116
A pathogen must survive to....
exit diseased host and infect new host
117
pathogens and host generally evolve towards......
balanced pathogenicity
118
What is balanced pathogenicity?
Pathogen becomes less virulent while host becomes less susceptible
119
What is an example of balanced pathogenicity?
Rabbits and myxoma virus
120
Adhesions attach to host cell _____________
receptor
121
Where are adhesions usually found?
At the tips of short pilli called fimbriae
122
Adhesions can be component of ____________ or various cell wall _______________
capsules, protiens
123
The binding of adhesions is highly _________________
specific
124
What does the binding of adhesions dictate?
the type of cell to which bacterium can attach as well as species - specificity
125
After attachment, the microbe must.....
multiply
126
Microbe may produce ________________ to bind iron
siderophores
127
Siderophores compete with _______________ and __________________ of host
lactoferrin and transferrin
128
Microbe must avoid secretory....
IgA
129
Why must microbe avoid secretory IgA?
rapid pili turnover, antigenic variation, IgA proteases
130
Microbe must compete with ______________ and tolerate _________________________
normal microbiota
toxic products of other microbes
131
Name the steps of establishing an infection
Adherence, Colonization, Immune Avoidance, Damage to Host, Exit and infect new host
132
Describe a Type III Secretion System.
Effector proteins induce changes (altering of cell's cytoskeleton structure)
Can induce uptake of bacterial cells
133
What organism uses a type III secretion system?
Salmonella
134
What type of cell uses a type III secretion system?
Gram negative cells
135
In directed uptake by cells, pathogen induces.....
non-phagocytic cells to engulf them via endocytosis
136
Actin molecules in host cells __________________ during directed uptake. This causes......
rearrange; causes membrane ruffling
137
What occurs after membrane ruffling?
ruffles enclose bacteria, bringing them into cell
138
The skin is a _____________ barrier to penetrate, therefore.....
difficult; bacteria rely on injuries
139
_________________ enters via a cut or wound
Staphylococcus aureus
140
_______________ is injected by fleas (all pathogens that employ insect or arthoprod vectors)
Yersinia pestis
141
What is the entry point for most pathogens?
mucous membranes
142
What are the two ways pathogens utilize mucous membranes?
- directed uptake by cells
- exploiting antigen-sampling processes
143
During the antigen- sampling process, what samples the material?
Mucosal-associated lymphoid tissue (MALT)
144
Some pathogens use ___________________ to cross intestinal barrier
M cells
145
____________ survives phagocytosis by macrophages
Shigella
146
After shigella induces apoptosis, it.....
binds to base of mucosal epithelial cells and induces uptake
147
Some pathogens invade by....
alveolar macrophages
148
What is an example of a pathogen that invades by alveolar macrophages?
Mycobacterium tuberculosis
149
Mycobacterium tuberculosis produces _____________, directs ____________, avoids _______________
surface proteins
uptake
macrophage activation
150
Hiding within a host cell allows....
avoidance of complement proteins, phagocytes, and antibodies
151
Shigella directs transfer from _____________________ to adjacent cells by causing host cell actin ___________________
intestinal epithelial cell
polymerization
152
What pathogen (besides Shigella) hides within a host cell?
Listeria monocytogenes
153
What does C5a peptidase do?
degrades chemoattractant C5a
154
What pathogen does C5a peptidase work in?
Streptococcus pyogenes
155
What do membrane-damaging toxins do?
kill phagocytes and other cells
156
S. pyogenes makes....
streptolysin O
157
What do capsules do?
interfere with opsonization; some bind host's regulatory proteins that inactivate C3b
158
What is an example of a pathogen that contains capsules?
Streptococcus pneumoniae
159
Using an M protein, the cell wall of Streptococcus progenies binds ____________________ and prevents __________ activation
regulatory protein
C3b
160
What do Fc receptors do?
bind Fc region of antibodies
161
Surviving within phagocytes allows pathogens to avoid ____________, controls some ________________, and move throughout the body
antibodies
immune responses
162
______________ produces molecule that forms pores in membrane
Listeria monocytogenes
163
___________ species lyse phagosome
Shigella
164
How do pathogens escape from phagosomes?
prior to lysis with lysosomes
165
How to pathogens avoid destruction?
prevent phagosome- lysosome fusion
166
___________ sense ingestion by macrophage, produce protein that blocks fusion process
Salmonella
167
___________________ (Q fever) can withstand environment, delays fusion, and allows time to equip itself for growth
Coxiella burnetii
168
What are examples of serum resisting bacteria?
Neisseria gonorrhoeaa and N. menigitidis
169
____________________ and _________________ hijacks mechanism that host uses to prevent their surfaces from activating complement
Neisseria gonorrhoeaa and N. menigitidis
170
Complement deficient individuals are ___________________ times more likely to come down with N. meningitides
1000 - 10,000
171
Organism binds complement regulatory proteins to avoid....
membrane attack complex (MAC)
172
IgA protease cleaves...
IgA found in mucus and secretions
173
What pathogens produce IgA protease?
Neisseria gonorrhoeae, Heamophilus influenzae, and others
174
What does antigenic variation imply?
alter structure of surface antigens, stay
ahead of antibody production
175
____________ varies antigenic structure of pili
Neisseria gonorrhoea
176
How do pathogens mimic host molecules?
cover surface with molecules similar
to those found in host cell, appear to be “self”
177
_____________ form capsule from hyaluronic acid, a polysaccharide found in _________________-
Streptococcus pyogenes
human tissues
178
What are direct effects of damage to host?
toxins produces
179
What are indirect effects of toxin to host?
immune response
180
Damage to host may help pathogen....
to exit and spread
181
_________________ induces watery diarrhea, up to 20 liters/day, which contaminates water supplies
Vibrio cholerae
182
____________________ triggers severe coughing, pathogens released into air
Bordetella pertussis
183
What are exotoxins?
proteins with specific damaging effects
184
When are exotoxins secreted into tissue?
following bacterial lysis
185
What are toxoids?
inactivated toxins
186
What are examples of toxoids?
tetanus, diptheria
187
What is antitoxin?
a suspension of neutralizing antibodies
188
Many diseases due to _______________________ were fatal before adequate immune response
toxin-producing bacteria
189
Neurotoxins damage....
nervous system
190
Enterotoxins cause.....
intestinal disturbances
191
Cytotoxins damage.....
variety of cell types
192
How are exotoxins grouped?
according to the tissues they affect and by their structure and mechanism of action
193
What are the three structures/ mechanism of action of exotoxins?
A-B toxins
Membrane-damaging toxins
Superantigens
194
Describe the structure of A-B toxins
Composed of two
subunits, A and B.
The A subunit is the
toxic, or active,
part; the B subunit
binds to the target
cell
195
What is the name of disease/ name of toxin for clostridium botulinum?
Botulism; botulinum toxin
196
How is Botulism characterized?
flaccid paralysis
197
What is the Mechanism of Clostridium
botulinum?
Blocks transmission of nerve signals to the
muscles by preventing the release of
acetylcholine.
198
What type of toxins are C. botulinum and C. tetani?
neurotoxins
199
What is the name of disease/ name of toxin for Clostridium tetani?
Tetanus; tetanospasmin
200
How is tetanus characterized?
Spastic paralysis
201
What is the mechanism for C. tetani?
Blocks the action of inhibitory neurons by
preventing the release of
neurotransmitters.
202
What is the name of disease/ name of toxin for Vibrio cholerae?
Cholera; cholera toxin
203
How is cholera characterized?
Severe watery diarrhea
204
What is the mechanism for Vibrio cholerae?
Modifies a regulatory protein in intestinal
cells, causing those cells to continuously
secrete electrolytes and water.
205
What type of toxin is vibrio cholerae?
enterotoxin
206
Name of disease/ name of toxin for Corynebacterium diphtheria
Diphtheria; diphtheria toxin
207
Which pathogens use Fc receptors?
Staphylococcus aureus, Streptococcus pyogenes
208
Characteristics of diphtheria
Pseudomembrane in the throat; heart, nervous system, kidney damage
209
Mechanism for Corynebacterium diphtheria
Inhibits protein synthesis by inactivating an elongation factor of eukaryotic cells. Kills local cells (in the throat) and is carried in the bloodstream to various organs.
210
Name of disease; name of toxin for Shiga toxin– producing E. coli (STEC)
Bloody diarrhea, hemolytic uremic syndrome; Shiga toxin
211
How is shiga toxin characterized?
Diarrhea that may be bloody; kidney damage
212
What is the mechanism for Shiga toxin– producing E. coli (STEC)?
Inactivates the 60S subunit of eukaryotic ribosomes, stopping protein synthesis.
213
Name of disease/ name of toxin for Shigella dysenteriae
Dysentery, hemolytic uremic syndrome; Shiga toxin
214
How is dysentery characterized?
Diarrhea that contains blood, pus, and mucus; kidney damage
215
Mechanism for Shigella dysenteriae.
Inactivates the 60S subunit of eukaryotic ribosomes, stopping protein synthesis.
216
Name the A-B Cytotoxins
Corynebacterium diphtheria
Shiga toxin– producing E. coli (STEC)
Shigella dysenteriae
217
Name the A-B enterotoxins
Vibrio cholerae
218
Name the A-B neurotoxins
Clostridium botulinum
Clostridium tetani
219
What type of toxin is Streptococcus pyogenes?
Membrane damaging cytotoxin
220
Name of disease/ name of toxin for Streptococcus pyogenes
Pharyngitis and other infections; streptolysin O
221
Characterize Pharyngitis
Accumulation of pus
222
What is the mechanism for Streptococcus pyogenes?
Inserts into membranes, forming pores that allow fluids to enter the cells. Lysing host cells: RBCs, leukocytes and others
223
Describe MEMBRANE-DAMAGING TOXINS (cytotoxins)
—Disrupt plasma membranes, causing leakiness that results in cell lysis.
224
What are super antigens?
Override the specificity of the T-cell response.
225
name of disease/ toxin for Staphylococcus aureus (certain strains)
Staphylococcal toxic shock; toxic shock syndrome toxin (TSST)
226
Characteristics of toxic shock syndrome
Fever, vomiting, diarrhea, muscle aches, rash, low blood pressure
227
What is the mechanism for Staphylococcus aureus?
Systemic toxic effects due to the resulting massive release of cytokines.
228
What type of toxin is S. aureus?
Superantigen
229
Some S. aureus causes.....
Scalded-skin syndrome; exfoliatin
230
What are the characteristics of Scalded-skin syndrome?
Separation of the outer layer of skin
231
What is the mechanism for Scalded-skin syndrome?
Destroys material that holds the layers of skin together.
232
What are the two parts of A-B toxins?
A (active) subunit is toxic, usually an enzyme
B subunit binds to cell, determines cell type to be infected
Many AB toxins have multiple B subunits (i.e. A1B5: cholera toxin; Shiga toxin
233
How does the structure of A-B toxins allow for novel approaches for vaccines and therapies?
can use B subunit to deliver medically useful compounds to specific cell type
234
What are membrane-damaging toxins?
cytotoxins that disrupt eukaryotic cytoplasmic membranes, lyse cells
235
What do hemolysins do?
lyse red blood cells
236
What do Pore-forming toxins do?
insert into membranes, form pores
237
Name examples of pore-forming membranes
Streptolysin O from Streptococcus pyogenes
238
What do phospholipase do?
hydrolyze phospholipids of membrane
239
Name an example of phospholipase?
alpha toxin of Clostridium perfringens (gas gangrene)
240
What are super antigens?
stimulate high number of helper T cells, causing cytokine storm
241
How do super antigens work?
Simultaneously bind MHC class II and T-cell receptor
In an antigen-non-restricted manner (i.e. every class II TcR pair)
T-cell interprets this as antigen recognition
242
Toxic effect from super antigens is from....
massive cytokine release
243
T cells undergo __________, which suppresses the immune response
apoptosis
244
Endotoxin ______________________________ found in outer membrane of Gram-__________ cell wall; contains lipid _____
lipopolysacharride
negative
A
245
What does lipid A trigger?
inflammatory response
246
When localized, Lipid A.....
helps clear infection
247
When systemic, Lipid A....
causes widespread response: septic shock or endotoxic shock
248
When is Lipid A released?
following cell lysis
249
Toll like receptors induce....
cytokine producion
250
T-independent antigen may activate....
a variety of B cells
251
What assay detects endotoxin?
Limulus amoebocyte lysate (LAL) assay
252
What can trigger sepsis and septic shock?
peptidoglycan
253
Endotoxins only form....
gram-negatives
254
Lipid A is heat...
stable
255
Bacterial source of exotoxins
gram positive and gram negative species
256
bacterial source of endotoxin
gram negative species only
257
Location in bacterium - exotoxins
Synthesized in the cytoplasm; may or may not be secreted
258
Location in bacterium - endotoxins
Component of the outer membrane of the Gram-negative cell wall
259
Chemical nature of exotoxins
protein
260
Chemical nature of endotoxins
Lipopolysaccharide (the lipid A component)
261
can exotoxins form a toxoid?
generally yes
262
can endotoxins form a toxoid?
no
263
Heat stability of exotoxins
Generally inactivated by heat
264
Heat stability of endotoxins
Heat-stable
265
Mechanism of exotoxins
A distinct toxic mechanism for each
266
Mechanism of endotoxins
Innate immune response; a systemic response can lead to fever, a dramatic drop in blood pressure, and disseminated intravascular coagulation
267
Toxicity of exotoxins
Generally very potent; some are among the most potent toxins known
268
Toxicity of endotoxins
Small amounts in a localized area lead to an appropriate immune response that helps clear an infection, but systemic distribution can be deadly
