Exam 3 Flashcards
1
Q
what does a vaccine contain
A
dead or weakened or subunits of pathogens that stimulate the immune system
2
Q
what do vaccines produce
A
Abs or CTL
- exactly like it would if you were exposed to the disease
3
Q
after getting vaccinated, what do you develop
A
immunity to that disease
4
Q
B cells need to be activated to become plasma cells to make Abs. Which cells need to be activated for this to occur?
- macrophages
- NK cells
- CD8+ T cells
- CD4+ T cells
A
CD4+ T cells
5
Q
CD4+ T cells recognize antigen presented on….
A
MHC 2
6
Q
in order to present on MHC 2, antigens must be processed via….
A
lytic enzymes in the phagolysome
7
Q
are antigens on MHC 2 exogenous or endogenous
A
exogenous
8
Q
memory CD4+ T and B cells are generated when…
A
- APCs engulf antigens and present peptides to CD4+ T cells
- B cells engulf antigens and become activated when they receive T cell help
9
Q
memory CD4+ T and B cells are produced efficiently even when
A
the microbe has not infected an APC
10
Q
true or false, in order to generate CTL, APCs need to be infected by the microbe
A
true
11
Q
memory CD8+ T cells are generated when…
A
when an APC becomes infected
- digests the antigen into peptides and presents it to CD8+ T cells (which receive T cell help)
12
Q
memory CD8+ T cells are produced when
A
the microbe infects an APC
13
Q
what are the two major categories of vaccines
A
- attenuated vaccines
- inactivated vaccines
14
Q
what are attenuated vaccines
A
they use a live/active but weakened form of the pathogen
- uses whole bacterial cells or viruses as the antigen
15
Q
can attenuated vaccines cause diseases
A
no
16
Q
what are inactivated vaccines
A
they are unable to replicate
17
Q
which of the following is an advantage to using an inactivated vaccine over a live attenuated vaccine?
- good Ab and cell-mediated responses
- requires fewer boosters and a lower initial dose
- confers longer-lasting immunity
- no risk of causing infectious disease
A
no risk of causing infectious disease
18
Q
what are considered safer, inactivated vaccines or live attenuated vaccines
A
inactivated vaccines
19
Q
do inactivated vaccines need boosters
A
yes
20
Q
inactivated vaccines come with a reduced ____ of the vaccine
A
effectiveness
21
Q
live attenuated vaccines production is usually done with
A
meticulous quality checks ensuring their safety
22
Q
for live attenuated vaccines who should be careful with those types of vaccines
A
pregnant women and immunocompromised people
23
Q
what are the four types of inactivated vaccines
A
- inactivated or killed whole agent vaccines = use killed whole cells or inactivated whole viruses
- subunit vaccines = use key protein antigens or antigenic fragments from a pathogen
- DNA or RNA vaccines = inject pieces of the pathogen’s genetic code
- vector vaccines = use a chemically weakened virus to transport pieces of the pathogen’s genetic code
24
Q
what do subunit vaccines often require
A
adjuvant = a chemical that enhances antigenicity by stimulating dendritic cells and macrophages
- boosts immune response
25
what are three types of subunit vaccines
- toxoids = contain inactivated exotoxin (toxin is modified to no longer have toxicity but still retain antigenic epitopes)
- polysaccharide vaccines = contain capsular polysaccharides
- conjugate vaccines = polysaccharides (usually capsule) linked to proteins
26
would a vaccine that contains bacterial capsule (ie a polysaccharide vaccine - T-independent) elicit a robust response in young children
no
27
are polysaccharides T-independent antigens or T-dependent antigens
T-independent antigens
28
polysaccharides (T-ind antigens) need to be ____ to a protein (T-depend antigens) to enhance their ___ in young children
conjugated; antigenicity
29
do T-independent antigens bind to other T-independent antigens
no
- T-independent antigens can only bind to other T-dependent antigens
30
do conjugate vaccines require T-cell help
no
31
the preparation of conjugates makes T-independent antigens into
T-dependent antigens
32
vaccination confers ___ ___ to the individual vaccinated
active immunity
33
true or false - some people believe that naturally acquired immunity is better than the immunity provided by vaccines
true
34
what are some usual side effects of vaccines
- local soreness at the injection site
- minor fever
- malaise
- feeling tired
35
what are two rare side effects of vaccines
- febrile seizures = convulsions in young children associated with high fever
- anaphylaxis = allergic reactions to chemicals other than the antigen which may be present in the preparations
36
what is microbiota
the microorganisms that normally colonize various sites on/within the body without causing disease
37
what are two different types of microbiota
1. resident microbiota = inhabit sites for extended periods
2. transient microbiota = inhabit temporarily for days, weeks, or months and then disappear
38
what does colonization mean
the ability of a microbe to stay affixed to a body surface and replicate
39
where do these microbiota colonize
nose, mouth, throat, skin, LI, urethra, and vagina
40
where in the body is free of microbes (sterile)
blood, CSF, and internal organs
41
part of our first line of defense against infection competitively exclude
pathogens
42
how does our first line of defense exclude pathogens
- covering of binding sites prevents attachment
- consumption of available nutrients
- production of compounds toxic to other bacteria
43
what does microbiota aid in
- digestion
- vitamin production
- drug metabolism
44
how is the microbiota acquired
- humans are initially colonized by microorganisms at birth
- after, the microbiota may continue to undergo small changes in response to external factors (diet, environment, interactions with other humans, etc.)
45
by age three, a child's microbiome looks a lot like
an adult's
- and becomes much more stable
46
microbiota changes in response to events like
- illness
- disease
- antibiotic treatment
- fever
- stress
- injury
- changes in diet
47
what is a pathogen
any bacterium, virus, fungus, protozoan, or helminth that causes disease
48
what is pathogenicity
the ability of an organism to cause disease
49
what are types of pathogenicity
- genetic makeup of the pathogen
- location in/on the host's body
- host immune response
50
what can true ("primary") pathogens cause
they can cause disease in a host regardless of the host's resident microbiota or immune system
51
are true pathogens ever part of the normal microbiota
no
52
what do opportunistic pathogens cause
disease only under opportunistic conditions, ie situations that compromise the host's defenses
53
opportunistic pathogens can be members of
normal microbiota or common in the environment
54
what are some situations that compromise the host's defenses
- changes in the composition of the normal microbiota (ie taking antibiotics)
- displacement of normal microbiota to another site in the body
- weakened immune system
- immune suppression (chemotherapy, organ
transplants)
- immunodeficiency (AIDS)
- old age or stress or other diseases
55
what are two examples of opportunistic pathogens
- candida albicans = a yeast found in the vaginal microbiota
- c. diff = a bacterium that can be part of someone's transient gut microbiota
56
what is c. diff resistant to
a lot of antibiotics
57
what does lactobacillus do in the vagina
it's a bacterium in the vagina that suppresses yeast growth
58
can someone be infected but not have an infectious disease
yes
59
what is an infection
a successful colonization and multiplication of microorganisms within a host with or without the manifestation of disease
60
what is an infectious disease
illness caused by damage to host cells by an infectious agent (bacteria, viruses, fungi, and parasites) or its products (exotoxin) resulting in signs and symptoms
61
what does virulence mean
the degree or severity of disease
62
pathogens differ in their ___ of virulence
degree
63
what are virulence factors
proteins and other molecules that contribute to the pathogen's ability to establish itself in a host or cause host damage
64
how can virulence be measured
by LD50 (lethal dose 50)
- the number of microbes that kills 50% of an experimental group of animal hosts
65
which LD50 would be more virulent - LD50 = 400 or LD50 = 600
LD50 = 400 because that means it will take less work to kill the organisms with the infection
66
what does infectious dose (ID) mean
the minimum number of microbes required to be taken in by the body to cause infection
67
what does ID50 mean
the number of microbes that will cause infection in approx. 50% of an experimental group of hosts
68
which is LEAST likely to cause an infection according to the data below
- E.Coli ; ID50 = 10-100
- Shigella dysenteriae ; ID50 = 10-200
- salmonella ; ID50 = 1,000
- vibrio cholerae ; ID50 = 1,000,000
- hepatitis A virus ; ID50 = 10-100
vibrio cholerae because it would take exposure to 1M host to infect 50% of the population
69
what are the four stages of pathogensis
1. adhesion = to skin or mucosa
2. invasion = through epithelium and immune evasion
3. infection = colonization and growth
4. tissue damage, disease
70
between what two stages of pathogenesis do toxins or host immune response occurs
between infection and tissue damage - disease
71
what are the six portals of entry
1. fecal-oral = through mucosal surfaces of GI tract
2. respiratory = through mucosal surfaces of respiratory tract
3. transplacental = through the placenta to infect a fetus
4. skin = through epithelial surfaces
5. urogenital = through mucosal surfaces of genital and urinary tracts
6. parenteral = through injection into the bloodstream (ex: insect bites or needle sticks)
72
what cellular structures help pathogens adhere
- fimbriae adhesions
- cell wall adhesions
- glycocalyx (slime and capsular polysaccharides)
73
how do pathogens invade tissue and evade host immune response
- invasion
- ability of some pathogens to spread through tissues
- produce enzymes or toxins which serve as virulence
factors that allow them to colonize and damage host
tissues as they spread deeper into the body
- immune evasion: antigenic variation
- acquire changes in the genes for surface antigens that
alter the structure of surface antigens that Abs would
otherwise recognize
74
how does replication within a phagocyte benefit the pathogen
- avoid recognition by phagocytes
- avoid recognition by complement
- avoid recognition by Abs
- all of the above
all of the above
75
what are four ways that intracellular bacteria survive within phagocytes
1. by preventing fusion of the lysosome with the phagosome
2. by escaping from the phagosome before the lysosome fuses
3. by preventing acidification of the phagosome
4. by resisting killing by lysosomal chemicals
76
once a pathogen is in, attached and evade the immune response, what does it do
it replicates and grows
77
true or false - with colonization and growth, new organisms must compete with established organisms for nutrients and space
true
78
what does localized mean
when pathogens grow locally at the site of the invasion
79
what does systemic mean
when pathogens may spread throughout the body
80
cellular damage can be a direct result of ___ or indirect via ___
- pathogen (such as toxin production)
- immune response
81
toxins may be transported by ___ or ____
blood; lymph
82
what are the two general types of toxins
1. exotoxins
2. endotoxins
83
what are exotoxins
proteins produced by pathogenic bacteria (gram positive and gram negative) and secreted
84
what are endotoxins
the lipid A portions of LPS that are part of the outer membrane of the cell wall of gram negative bacteria
85
when are endotoxins liberated
when the bacteria die and the cell wall breaks apart
86
how do you name exotoxins
- by types of cell affected
- by associated disease
- by bacterium producing it
87
what are the three major modes of exotoxins' action
1. cytolytic toxins
2. AB toxins
3. superantigen toxins
88
what does cytolytic toxins do
they work by disrupting cytoplasmic membrane integrity, causing cell lysis and death
- toxins that lyse RBCs are called hemolysins
89
what do AB toxins do
consist of two subunits, A and B
- B binds to host cell receptor and transfers subunit A (the toxic part) across the cell membrane
- usually inhibits protein synthesis or disrupts ion homeostasis aka intracellular-targeting toxins
90
what do superantigen toxins do
overactivate the immune system by activating non specifically CD4+ T cells which leads to an excessive cytokine release and excessive inflammatory response
91
where do bacteria get their exotoxin genes
horizontal gene transfer
- most genes for exotoxins are carried on plasmids or phages
92
how does the body fight exotoxins
the body makes Abs (antitoxins) -> provide immunity
93
how are exotoxins inactivated
by heat or chemical -> toxoid vaccine to stimulate antibody production
94
an example of an endotoxin is Lipid A (the toxic part), what happens when LPS gets into the circulation
it can trigger a massive inflammatory response
95
endotoxin - excessive release of cytokines from host is called
cytokine storm
96
what do endotoxin induce
inflammatory trauma throughout the entire body
- fever, shock, disseminated intravascular coagulation, and death
97
what are some mechanisms of bacterial pathogenesis
- produce toxins that are ingested
- colonize and invade host tissues
- colonize and produce toxins (no invasion)
- colonize and invade host tissues, produce toxins
98
what is epidemiology
the science that underlies public health
99
what does epidemiology study
how disease originates and spreads throughout a population
100
what is the goal of epidemiology
to prevent outbreaks and contain them when they do occur
101
what are four patterns of infectious disease occurrence
1. endemic = disease consistently present (often at low level) in a population
2. sporadic = when occasional cases are reported at irregular intervals
3. epidemic = occurrence of more cases of disease than expected in a given area over a particular period of time ("outbreak")
4. pandemic = an epidemic occurring on several continents and usually affecting an exceptionally high proportion of the global population
102
what does prevalence mean when measuring disease frequency
- number of existing cases of disease in a population during a defined period of time
- individuals with outcome of interest, regardless of when diagnosed
- how much of a population is affected
103
what does incidence mean when measuring disease frequency
- number of new cases of disease that develop in a population during a defined period of time
- individuals who change in disease status over a specified period of time
- how quickly are people becoming infected
104
what does mortality rate mean
incidence of death due to a disease during a particular time period
105
what does case fatality rate mean
mortality rate/incidence rate
106
are all infectious diseases contagious
no
107
true or false - an infectious disease may or may not be communicable
true
108
what is a communicable disease
an infectious disease that is contagious and which can be transmitted from one infected host to another
- reproductive number R0 is a measure of contagiousness
109
during which period can a host be contagious
- incubation period
- prodromal period
- period of illness
- period of convalescence
- all of the above
all of the above
- but depends on the infection
110
which stage is an infection transmissible
transmissible during any of the stages depending on the pathogen
111
what are the two types of contact transmission
1. direct
- skin-skin
- mucous-mucous (sexually transmitted)
- across placenta
- through breast milk
2. indirect
- droplets = close range (ie respiratory droplets) inhaled by someone close by)
- fomites = inanimate objects that transmit pathogens (ie doorknobs)
112
what are three types of vehicle transmission
1. air-borne
- aerosols
- droplet nuclei inhaled by those over a long distance
2. food-borne
3. water-borne
113
droplet transmission vs airbone transmission
- droplet transmission = coughs and sneezes can spread droplets of saliva and mucus; droplets fall down within three feet of host (more than 5 microns)
- airborne transmission = tiny particles, possibly produced by talking, are suspended in the air for longer and travel further; droplet nuclei travel further, >3ft (less than 5 microns)
114
what is vector transmission
- living organisms that can carry pathogens
- arthropods: insects (flies, mosquitos) and arachnids (mites, ticks, and spiders)
115
what is a reservoir
- where microorganisms can live, accumulate, or persist outside of the host of interest
- serves as a source of infection for other host organisms
116
what are three types of reservoir
- human reservoir
- animal reservoir
- non-living reservoir
117
how can a human act as a carrier
a human acting as a reservoir of a pathogen may or may not be capable of transmitting the pathogen
118
what is a human reservoir capable of transmitting
a pathogen who do not present signs or symptoms of disease is an asymptomatic carrier
119
what are zoonoses
diseases that can be transmitted from animals to humans
120
true or false - 75% of all emerging infectious disease are zoonotic
true
121
what type of people are at highest risk of zoonotic infections
people who are more likely to come into contact with animals or who share air and space with animals
122
how are zoonotic diseases acquired
through various routes
123
in zoonoses animals are the ___ host
definitive
124
in zoonoses humans are typically __-__ host
dead-end
125
what are three types of durations of the disease
1. acute disease = symptoms develop rapidly (strep throat)
2. chronic disease = symptoms develop gradually over months, years, or lifetime and are slow to resolve (hepatitis C)
3. latent disease = the casual pathogen goes dormant for extended periods of time with no active replication
- no symptoms unless organism reactivates and infection again becomes acute (cold sores due to Herpes)
126
are latent organisms ever eliminated
no
127
which bacteria are gram positive
- staphylococcus
- streptococcus
- bacillus
- clostridium
- corynebacterium
128
which bacteria are atypical
- mycoplasma (no cell wall)
- mycobacterium (acid-fast cell wall)
- spirochetes (thin cell wall) includes Treponema and Borrelia
129
what is the most virulent staphylococcal species
s. aureus
130
what does s. aureus produce
- impetigo
- TSS
- SSS
- food poisoning
- folliculitis, carbuncle, and furuncle
131
what kind of virulence does s. epidermidis (CoNS) have
low virulence
132
true or false - s. epidermidis is the normal microbiota of the skin
true
133
what does s. epidermidis cause
opportunistic infections
134
what are some characteristics of s. aureus used in clinical diagnosis to distinguish s. aureus from other species
- coagulase production
- pigment production (hemolysis)
- fermentation of mannitol and halotolerance
135
is s. aureus coag positive or negative
positive
- have solid at the bottom
136
is s. epidermidis coag positive or negative
negative
- going to be liquid
137
different types of hemolysis on blood agar
- B-hemolysis = complete hemolysis (halo)
- alpha-hemolysis = incomplete hemolysis -> green pigment
- y-hemolysis = no hemolysis (clear)
138
what type of hemolysis is s. aureus
b-hemolytic
- produces hemolysins called staphylolysins
139
what type of hemolysis is s. epidermidis
y-hemolytic
140
what does mannitol salt agar inhibit
the growth of many organisms EXCEPT staphylococci which is halotolerant (ie facultative halophile)
141
organisms that ferment mannitol are detected by a change in the
pH indicator from red to yellow
142
what type of media is mannitol-salt agar
- selective
- differential
- general purpose
- enriched
- selective and differential
selective and differential
143
how do we distinguish staphylococcus from streptococcus
staphylococci produce catalase
144
what does catalase break down
hydrogen peroxide (H2O2) produced during oxidative metabolism
- bubbles will appear
145
do streptococci produce catalase
no
146
how is s. aureus resistant to penicillin
because it produces beta lactamase (penicillinase) and thus is resistant to penicillins and cephalosporins
147
do streptococci produce beta lactamase
no most strepc don't, therefore remain sensitive to beta lactam antibiotics
148
true or false - s. epidermidis are relatively avirulent
true
149
what helps s. epidermidis adhere to devices
the production of slime layer because it forms biofilms on the devices (catheters, shunts, prosthetic joints, etc)
150
when does s. epidermidis become opportunistic infections
when introduced into deeper tissues or a normally sterile site
151
when are opportunistic infections of s. epidermidis usually acquired
during a hospital stay
152
what is the major cause of hospital acquired infections
s. epidermidis
153
what are some examples of infections that were hospital acquired s. epidermidis infections
- subacute endocarditis
- infections of foreign bodies (ie catheters, shunts, prosthetic joints, etc) and urinary tract infections
154
is s. aureus very contagious
yes
155
who are the main reservoirs for s. auerus
humans
156
about 30% of healthy adults are ___ __ for s. aureus
nasal carriers
157
what are the three types of transmission of s. aureus
1. direct skin to skin contact
2. indirect contact via fomites
3. ingestion of contaminated food
158
s. aureus has a high tolerance to
salt and desiccation (drying conditions)
159
what are the major virulence factors of s. aureus
- capsule
- catalase
- exotoxins: enterotoxin, TSST-1, and exfoliative toxin
- coagulase
- staphylolysin
- leukocidin
- protein A
- hyaluronidase
160
what are virulence factors
they can be genetic, biochemical, or structural features that enable an organism to produce disease
161
pathogenesis may depends on
a single or multiple virulence factors
162
how do strains of s. aureus differ
by which virulence factors they produce
- some strains are more virulent because they make more virulence factors
163
for most disease caused by s. aureus, pathogenesis depends on the combined actions of
several virulence factors
164
what does catalase do
neutralizes hydrogen peroxide
- a type of ROS
- counteracts phagocytes' oxidative killing
165
what does capsule do
inhibits phagocytosis
- composed of polysacchs
166
which virulence factors are exotoxins that were produced by s. aureus
- staphylolysin
- enterotoxin
- toxic shock syndrome toxin 1 (TSST-1)
- exfoliative toxin
167
what does stphylolysin do
lyses RBCs and WBCs
168
what is an enterotoxin and what does it act as
it is a potent GI toxin as well as superantigen activity
169
what does TSST-1 act as
a potent superantigen
170
what does exfoliative toxin do
an exotoxin that causes desquamation of the skin, weak superantigen activity
171
how do coagulase, protein A, catalase, and capsule contribute to s. aureus virulence?
- destroy human host cells
- allow the bacterium to invade mucosal tissues
- prevent phagocytosis
- act as endotoxin, inducing septic shock
- make the bacteria resistant to antibiotic treatment
prevent phagocytosis
172
is hyaluronidase a major virulence factor of s. aureus
yes
173
what does hyaluronidase do
degrades hyaluronic acid that cements cells together to promote spreading through tissues
174
what diseases cause more frequent and varied types of disease than any other human pathogen
s. aureus diseases
175
what are the three toxin-mediated s. aureus diseases
1. staphylococcal food poisoning
2. scalded skin syndrome
3. toxic shock syndrome
176
s. aureus is the most common cause of
pyogenic skin infections called pyodermas
177
what does pyogenic mean
pus producing
178
pyogenic infections are characterized by the formation of an
abscess
179
what are four diseases of localized skin infections
1. folliculitis
2. furuncle
3. carbuncle
4. impetigo
180
what is an abscess
a localized collection of pus surrounded by fibrin
181
what does pus contain of
debris consisting of dead PMNs and epithelial cells, dead and live bacteria and edema fluid
182
what is folliculitis
infection of hair follicle
- superficial pustule (pus filled vesicle)
- usually mild, resolves, or progresses to furuncle
183
what is a furuncle
aka boil; large painful lesion that extends from hair follicles to surrounding tissues
- abscesses in the skin involving subcutaneous tissue
- resolves or progresses to carbuncle
184
what is a carbuncle
multiple interconnected abscesses forming from the aggregration of furuncles
- extends deeper into the tissue
- requires debridement and antibiotics
185
what is the most common type of pyoderma
impetigo
186
what does impetigo look like
- small flattened red patches
- pus filled vesicles
- rupture and crust over
187
what are the symptoms of impetigo
usually little fever or pain
- nearby lymph nodes often enlarge
- itchy and highly contagious
188
impetigo is common among ____ and ___ ___
infants and young children
189
impetigo can also be caused by
streptococcus pyogenes
190
gastroenteritis is commonly caused by
bacteria, viruses, or toxins
191
when is it called food poisoning
when gastroenteritis is caused by a toxin and not an infection
192
staphylococcal food poisoning is an example of..
- infection
- intoxication
- infection and intoxication
intoxication
193
if its intoxication and not an infection, what is the onset and recovery
- has a rapid onset, usually within 4 hours
- rapid recovery usually within 24 hours
194
what are the symptoms of staphylococcal food poisoning
nausea and vomiting
195
does staphylococcal food poisoning have fever as a symptom
no
196
what can staphylococcal enterotoxin cause
food intoxication
197
what are some characteristics of staphylococcal enterotoxin
- resistant to low pH (stomach acid)
- heat stable
- superantigen activity
198
why do you think the blood cultures failed to isolate any pathogens
- s. aureus is too difficult to grow up in the lab
- s. aureus is too small to detect on a light microscope
- the cell wall of s. aureus does not react with the gram stain and therefore went undetected
- there were no bacteria in the blood samples because replicating bacteria were not causing the systemic disease
- fever is not a typical sign of a bacterial infection so it is probably caused by a virus
there were no bacteria in the blood samples because replicating bacteria were not causing the systemic disease
199
when does toxic shock syndrome (TSS) sometimes occur
as a complication of other localized or systemic infections such as skin wounds
200
what is TSS caused by
TSST-1
201
what is TSST-1
an exotoxin that induces fever, vomiting, rash and shock
202
what does TSST-1 act as
a potent superantigen
203
TSST-1 causes ___% of all cases
75%
204
TSS can also be caused by
streptococci
205
what are some symptoms of TSS
- abrupt onset of high fever (102F or above)
- red erythematous (sunburn-like) rash
- desquamation
- hypotension -> multi system organ failure
206
staphylococcal scalded skin syndrome (SSSS) is a ___ infection and a ____ intoxication
localized; systemic
207
SSSS is caused by
exfoliative toxin
208
what is an exfoliative toxin
an exotoxin that causes desquamation of the skin
- also acts as superantigen, but weaker than TSST-1
209
what are the symptoms of SSSS
erythema (redness) followed by desquamation
- no scarring
210
SSSS typically affects
neonates and infants
211
what is a potential complication of SSSS
a secondary infection is more likely to occur in the of areas where the skin has peeled away
212
how do manage staphylococcal infections
- boils, carbuncles may require minor surgery to drain pus
- antibiotic treatment often follows debridement (removed of dead/damaged tissue)
- staphylococci produce penicillinase (a type of beta lactamase)
213
what are MRSA strains resistant to
beta lactam antibiotics
214
what are MRSA strains sensitive to
vancomycin
215
what are VRSA associated with
worse outcomes such as longer hospital and ICU stays and higher mortality rates
- many hospitals now screen patients to limit spread
216
is streptococcus gram positive or negative
positive
217
is strepcoc catalase negative or positive
negative
218
what is strepcoc sensitive to
- heat
- drying
- high salt concentration
- penicillin (most)
219
what are three classification points of strepcoc
1. species determined by biochemical tests or DNA sequencing
2. group-specific antigens (Lancefield classification)
3. hemolytic pattern on blood agar
220
what is the lancefield classification
is based on differences in a surface antigen (serotypes) called the cell wall C carbohydrate
221
what is the name of group A of lancefield classification
streptococci: S. pyogenes
222
what is the name of group B of lancefield classification
streptococci (GBS): S. agalactiae
223
what groups of streptococci have no lancefield group classification
- pneumococci
- viridans
224
what is lancefield grouping based on
serotpye
225
what is a serotype
a difference in the antigenic composition of a structure or product
226
how do we identify serotypes
use Abs (ie antisera) to detect differences in antigens that are unique to a particular species or a strain within a species
227
which groups identify as beta-hemolytic strep
- S. pyogenes
- S. agalactiae
228
which groups identify as alpha-hemolytic strep
S. pneumonia
229
which group identify as alpha or gamma hemolytic strep
viridans group strepcoc
- includes S. mutans (alpha hemolytic)
230
how to differentiate between S. pyogenes from S. agalactiae
both are beta hemolytic
- but s. aga is group B and bacitracin resistant
- s. pyo is group A and bacitracin sensitive
231
how is S. pyogenes transmitted
via respiratory droplets or direct skin contact
232
S. pyogenes frequently infect
skin or nasopharynx
233
what is the reservoir for S. pyogenes
humans
234
S. pyogenes cause ___% of streptococcal disease
90%
235
what are some diseases S. pyogenes cause
- pyogenic = "pus-producing"
- streptococcal pharyngitis
- impetigo
- cellulitis
- toxigenic
- toxic shock syndrome
- necrotizing fasciitis (also pus producing)
236
both S. pyogenes and s. aureus cause the disease, imeptigo. Which of the following is a characteristic that distinguishes these two genera
- catalase
- gram stain reaction
- hemolysis on blood agar
- cellular morphology
catalase
- S. pyogenes is catalase negative
- s. aureus is catalase positive
237
what are some characteristics of s. aureus
- (gram (-) or (+) coccal morphology
- catalase (-) or (+)
- coagulase (-) or (+)
- what type of hemolytic
- strains or serotypes,
- penicillin resistant or sensitive
- how does it grow on media
- gram (+) coccal morphology
- catalase (+)
- coagulase (+)
- beta-hemolytic
- multiple strains
- penicillin-resistant
- halotolerant
238
what are some characteristics of S. pyogenes
- (gram (-) or (+) coccal morphology
- catalase (-) or (+)
- coagulase (-) or (+)
- what type of hemolytic
- strains or serotypes,
- penicillin resistant or sensitive
- how does it grow on media
- gram (+) coccal morphology
- catalase (-)
- coagulase (-)
- beta-hemolytic
- multiple serotypes (80 M protein types)
- penicillin-sensitive
- fastidious, grow on enriched media
239
for virulence factors of S. pyogenes what factors inhibit host immunity
- hyaluronic acid capsule
- M protein
240
for virulence factors of S. pyogenes what are adhesive/invasive factors
- M protein
- hyaluronidase
241
what are some exotoxins of S. pyogenes
- cytolytic exotoxins: Streptolysin O and S
- pyrogenic exotoxins: SpeA and SpeB
242
what are antiphagocytic virulence factors by S. pyogenes
- hyaluronic acid capsule
- mimics the hyaluronic acid found in human
connective tissue
- hides the bacteria from phagocytes
- M protein
- important adhesion
- prevents opsonization by breaking down
complement, C3b
- more than 80 antigenic types of M protein
- Abs to one strain do not stop others
243
once you are infected with a pathogen, you develop immunity. Why is it then that children often get recurrent strep throat infections
- the innate immune system clears the infection before memory develops
- S. pyogenes destroys memory T and B cells
- S. pyogenes bacterial DNA integrates into host DNA to establish latency. Later it can be reactivated to cause disease
- they are becoming infected with different serotypes of S. pyogenes
they are becoming infected with different serotypes of S. pyogenes
244
what is streptolysin O
lyses leukocytes and erthrocytes
245
what is spe A
superantigen that causes helper T cells to release a cytokine storm leading to toxic shock
246
what is spe B
protease that destroys tissue, leading to fluid accumulation in the areas of damage
247
the genes of spe A and spe B are encoded by a
temperate bacteriophage
248
only ___ S. pyogenes strains can synthesize spe A and spe B
lysogenized
249
what does lysogenized mean
when a bacteria is infected with a temperate phage
250
what can phages carry
genes for exotoxins or other virulence factors
251
what is lysogenic conversion
new host phenotype due to expressed genes from a phage
252
for S. pharyngitis (strep throat) - are S. pyogenes inhaled
yes
253
in S. pharyngitis where does bacteria replicate
in mucosa of the pharynx
254
what are some symptoms of S. pharyngitis
- sudden onset of sore throat with patches of pus on tonsils, in back of throat
- tonsils may be swollen, red, and tender
- swallowing is painful
- fever
255
30% of pharyngitis cases in children are due to __. ___ (most other cases are viral)
S. pyogenes
256
what is absent in S. pharyngitis in children
absence of cough and nasal discharge
257
what is present in S. pharyngitis in children
presence of pus on tonsils
258
S. pharyngitis is most common in _ - __ year old children
5-10
259
how does impetigo enter
through the skin that is already irritated or raw
260
what does impetigo look like
small, flattened, red patches that develop into pustules that eventually rupture and crust over with a honey colored crust
261
is impetigo highly contagious
yes
262
impetigo is caused S. pygoenes, which other pathogen is it caused by
S. aureus
263
true or false - cellulitis spreads to the deeper demis and subcutaneous tissues
true
264
what are some symptoms of cellulitis
- fever
- chills
- leukocytosis
265
what does cellulitis present as
red puffy patches with ill-defined edges
266
what ages does cellulitis usually occur in
middle-aged and elderly
267
necrotizing fasciitis also means
flesh eating disease
268
what is necrotizing fasciitis caused by
highly virulent strains that produce spe A and spe B as well as other enzymes such as streptolysin O
269
what does necrotizing fasciitis infect
a wound that can be very minor
270
the enzymes and toxins in necrotizing fasciitis allow the bacteria to
invade and destroy muscle, fat, and organ fascia
271
true or false - necrotizing fasciitis has a strong inflammatory response
true
272
what does necrotizing fasciitis cause the skin to do
to swell, which stretches and discolors the skin
273
is the pain level consistent with the severity of the original injury in necrotizing fasciitis
no
274
what will happen is necrotizing fasciitis goes without treatment
- streptococcal toxic shock
- multi-organ failure
- death
275
what kind of disease is strep toxic-shock syndrome (TSS)
toxigenic disease
276
what is strep TSS caused by
strep pyrogenic exotoxin (spe A and B) and additional virulence factors
277
what does pyrogenic mean
exotoxins that generate a fever
278
true or false - strep TSS is less common but more deadly than staph TSS (caused by s. aureus)
true
279
what are some symptoms of strep TSS
- high fever
- diffuse sunburn-like rash
- hypotension
- shock
- multi-organ failure
- but may also include necrotizing fasciitis
280
strains of strep pyogenes that cause toxic shock syndrome must be infected by a phage
- true or false
true
281
what shape is s. pneumoniae
lancet (blade) - shaped diplococci
282
what type of hemolytic is s. pneumoniae
alpha-hemolytic
283
is s. pneumoniae capsule antiphagocytic
yes
284
the makeup of the polysacch s. pneumoniae capsule differs from ___ to ___
strain to strain
285
more than 90 different serotypes of S. pneumoniae have been identified based on
capsule structure
- all of which are capable of causing infections
286
what type of test does s. pneumoniae capsule use
quellung test
287
what is a quellung test
a biochemical reaction in which Abs bind to a bacterial capsule
288
what does a positive quellung test reaction cause
the capsule to become opaque and swell and enlarge
289
what is quelleung test used to serotype
s. pneumoniae
290
is s. pneumoniae quellung (+) or (-)
positive
291
what is s. pneumoniae reservoir
human carriers
292
where are s. pneumoniae located
transient part of the normal microbiota of the nasopharynges (20-60% kids are nasal carriers)
293
how are s. pneumoniae transmitted
via contact with respiratory droplets
294
s. pneumoniae disease causes disease typically in
very young and very old people
295
true or false - s. pneumoniae disease can cause otitis media (ear infection) and pneumonia
true
296
s. pneumoniae disease is the number one cause of ___ ___ in infants and young children
otitis media (ear infection)
297
s. pneumoniae disease is the number one cause of community-acquired ____ ___ in older adults
bacterial pneumonia
- also in immunocompromised, including smokers, diabetics, and alcoholics
298
what is the biggest risk factor of getting a bacterial ear infection
viral infections of the upper respiratory tract (URT), ie colds
299
otitis media by s. pneumoniae - viral URT infections create ___
exudate
- washes bacteria from the nasopharyngeal microbiota into the middle ear by Eustachian tube
300
what are some symptoms of otitis media
- inflammation
- swelling
- fluid, pus collect behind eardrum
- cause pressure where eardrum may burst
301
for pneumococcal pneumonia, humans are the carriers and the risk of pneumonia rises when
mucociliary escalator is damaged/non functional
302
is there microbiota in the lungs
no
- that means that bacteria can rarely reach the lung
303
pneumonia pathogenesis predisposing factors include
- ciliated epithelium damaged by viruses, smoking, and chemicals
- bacteria enter LRT and infect alveoli
- inflammation = fluid accumulation
304
what is the development of pneumonia
- growth of strepcocci on damaged ciliated epithelium
- growth in alveoli, which stimulates increased fluid accumulation
305
what are some signs and symptoms of pneumonia
- cough, fever, congestion, chest pain, rust-tinged sputum
- breathing becomes shallow and rapid
- skin becomes dusky due to poor oxygenation
- night sweats
306
how to diagnose pneumonia
- cheat radiograph confirm infiltrates (some kind of fluid)
- gram stain of the patients sputum (diplococci is gram (+))
307
what. are two vaccines against pneumococcal capsule
1. for children 2mo - 5yo -> pneumococcal conjugate vaccine (PCV13)
- 13 valent = protection against 13 serotypes
(strains)
2. for adults 65yos or older -> pneumococcal polysaccharide vaccine (PPV)
- 23 valent
308
is pneumococci enters the bloodstream what does it lead to
meningitis or sepsis
309
what is sepsis
an infection-induced systemic inflammatory response syndrome
310
what does sepsis cause
- vasodilation
- increased WBCs
- leakage of fluid from capillary beds
- remote from site of infection
311
what is the most common cause of sepsis
bacteremia (bacteria in the blood)
312
when does sepsis occur
when a pathogen that has entered the bloodstream overwhelms our innate immune response and replicates at high numbers
313
what are the steps in sepsis
1. infection of the bloodstream
2. excessive inflammation
3. cytokine release ("cytokine storm")
4. complement is also activated, further amplifies
5. additional phagocytes recruited, further amplifies
6. cell/tissue damage
314
what does "shock" mean in septic shock
general term used to describe cardiovascular collapse
- meaning the heart fails and there is not enough blood pressure to perfuse the tissues
315
what is septic shock
sepsis plus persistent hypotension despite adequate fluid resuscitation
316
s. agalactiae can also mean
group B strep (GBS)
317
GBS is the most common cause of
- neonatal sepsis
- neonatal meningitis
318
GBS is the second most common cause (after E. Coli) of
neonatal pneumonia
319
s. agalactiae is the transient part of the
normal vaginal microbiota
- in 25% of all healthy adult women
320
true or false - s. agalactiae cannot be transferred to infant during delivery
false
- it can
321
how is s. agalactiae virulence determined
by its ability to avoid phagocytosis (mediated by capsule)
322
to screen a pregnant women for GBS, at how many weeks would the screen occur
at 35-37 weeks by a vaginal and rectal swab
323
if the pregnant women was GBS+ what would happen next
would administer intrapartum antibiotics via IV to prevent transmission to neonate
324
s. mutan is a member of ___ group strepcocci
viridans
325
what type of hemolytic is s. mutans
alpha hemolytic
326
are s. mutans encapsulated or non-encapsulated
non-encapsulated so quellung (-)
327
what mirobiota is s. mutans a part of
normal oral microbiota
328
what kind of environments do s. mutans thrive in
acidic ones
329
what is s. mutans involved in
pathogenesis of dental caries (ie cavities)
- s. mutans begins the formation of biofilm on teeth
- bacteria ferment dietary carbs producing lactic acid
- lactic acid eats away a tooth enamel
330
what can provide pathogens an entry into the skin
cuts, punctures, burns, abrasions, and insect or tick bites that can break the barrier and provide entry for pathogens
331
skin infections can also occur when microorganisms enter the body from another site, like ___ or __ system, and then carried by the bloodstream to the skin
respiratory; GI
332
which host pathogens cause the majority of bacterial skin infections
staph aureus and strep pyogenes (group A)
333
what bacterial infections do s. aureus and s. pyogenes cause
impetigo, folliculitis, carbuncles, furuncles, cellulitis, and scalded skin syndrome (SSS)
334
what skin infections do s. aureus and s. pygoenes cause
- lyme disease = circulatory disease that produces a skin rash
- gas gangrene = wound infection
- tetanus = wound infection
335
what are some viral diseases that produce skin rashes
- varicella (chicken pox)
- zoster (shingles)
- measles
- rubella
336
what is one fungal disease (mycoses)
tineas
337
what is the most common vector-borne disease in the U.S.
lyme disease
338
how is lyme disease transmitted
via a bite from an infected black-legged lxodes tick
339
what causes lyme disease and what are its characteristics
borrelia burgdorferi
- gram negative spirochete and motile
340
true or false - spirochetes have an outer membrane containing LPS
true
341
what are some characteristics of spirochetes
- possess endoflagella
- moves in corkscrew fashion through its environment
- might enable pathogenic spirochetes to burrow
through hosts' tissues
342
what type of disease is lyme disease and what is its animal reservoir
it is a zoonotic disease
- white footed mouse is the main reservoir
343
true or false - borrelia burgdorferi (that causes lyme disease) is maintained in mice out in nature
true
- that is why they are the main reservoir
344
when it comes to lyme disease, what occurs in acquisition
unfed larva to fed larva in 3-5 days
345
when it comes to lyme disease, what occurs in transmission
unfed nymph to fed nymph in 3-5 days
346
when a nymph or adult tick infects a human, what is the human considered
accidental host ?
347
what are the three stages of lyme disease
1. multiply, migrate outward in circular fashion; LPS causes inflammatory reaction in skin
2. enter bloodstream, disseminate
3. immune system responds and causes damage to host tissue
348
what is stage 1 (erythema migrans) of lyme disease
- about 7 days after a tick bite
- bull's eye rash called erythema migrans
- flu-like symptoms
349
describe stage 2 (injury to nervous and cardiac system) of lyme disase
- 2-8 weeks after the tick bite
- nervous system is affected
- dizzy spells, fainting, difficulty concentrating
- paralysis of face, Bell palsy
350
describe stage 3 (immune response damages host tissue) in lyme disease
- about six months after tick bite
- arthritis with severe joint pain and swelling, particularly in the knees
- sometimes meningitis or encephalon
- most likely immune-mediated
351
what is the treatment for lyme disase
- antibiotics effectively treat first stage of lyme disease
- treatment of later stages are difficult
352
how is lyme disease prevented
- prevention is best achieved by avoiding ticks
- no available vaccine for humans
353
what are dermatophytes and what they do they include
- are a group of skin-invading molds
- include members of genera Epidermophyton, microsporum, and trichophyton
354
what can dermatophyes invade
keratinized layers of skin, hair, and nails
- produce keratinase, which breaks down keratin, using it as a nutrient source
355
how are skin diseases caused by fungi (mycoses) transmitted
fomites or direct contact
356
what do dermatophytes cause
tineas
- ringworm
- athlete's foot
- toenail fungus
357
what is ringworm
- tinea corporis
- scaly skin in the center surrounded by a raised red
margin that occur on smooth skin
*common in young children*
- tinea capitis
- severe cases affect scalp and hair-bearing region causing patchy areas of hair loss
358
what is athlete's foot
- tinea pedis
- more common in adults than in children
- scaly itchy rash between toes
359
what is nail fungus - onychomycosis
- tinea unguium
- very common but more common among the elderly
- about 10% of the general population
- chronic infection of the nails
- infected nails of the hands and feet become thickened, yellow, and brittle
360
true or false - normal microbiota or microorganisms from air, fingers, or object contaminate wounds
true
361
infection from a wound contamination can result in
- an abscesses by s. aureus
- wounds with extensive tissue damage and damaged blood supply create anaerobic conditions allow growth of obligate anaerobes such as clostridium tetani
362
what are some characteristics of clostridial species
(spp)
- endospore-former
- gram positive rods
- obligate anaerobe
363
what are four major clostridial pathogens
- c. perfringens = gas ganagrene
- c. tetani = tetanus
- c. botulinum = botulism
- c. difficile = antibiotic-associated pseudomembranous colitis
364
obligate anaerobe spores can survive in exposure to
air
365
C tetani spores enter the body and germinate in
damaged/necrotic tissue
366
tetanospasmin is a type of
A-B exotoxin
367
the tetanus toxin is taken up by inhibitory neurons where it
prevents release of inhibitory NTs (GABA)
368
what is tetany (aka spastic paralysis)
when the muscles undergo sustained contractions because the excitatory neurons are now unopposed by inhibitory neurons
369
death from tetany usually results from
respiratory failure
370
what is the treatment for tetany
- muscle relaxants
- human tetanus immune globulin (TIG) injection
- Abs bind to free toxin molecules, provide passive
immunity
- clean the wound
- antibiotics
371
how to prevent tetany
DTaP vaccine
372
what does DTaP vaccine protect against
diphtheria, tetanus, and pertussis
373
what does DTaP vaccine contain, does it need boosters, if so how often
- contains toxoid (inactivated tetanospasmin)
- requires boosters (Td or Tdap) every 10 years
374
true or false - tetanus is the only non-contagious disease we routinely vaccinate against
true
375
what are some characteristics of clostridium perfringens
- soil bacterium
- spore former
- gram positive rods
- obligate anaerobe
376
how do spores enter in c. perfringens
via severe and open wounds
- the organism requires damaged tissue with disrupted blood supply (ie anaerobic conditions) to germinate
377
what are some signs and symptoms of c. myonecrosis
- severe pain
- thin bloody or brownish exudate leaks from wound
- gas bubbles in tissue
- overlying skin stretched tight and mottled with black
- victim remains alert until late in illness, then becomes delirious and goes into coma
378
what are some c. perfringens virulence factors
- alpha toxin destroys PMNs, RBCs, and muscle tissue -> causing myonecrosis (death of muscle)
379
what is the treatment of gas gangrene
- prompt debridement of diseased tissue and amputation of all devitalized tissue
- antibiotics and antitoxin although less effective
- hyperbaric oxygen therapy
380
what virus is measles caused by
rubeola virus
- an enveloped virus
381
measles epidemiology
- humans are the reservoir
- usually affects young children
- transmission: respiratory droplet nuclei (airborne - vertical transmission)
382
what is the most contagious of the vaccine-preventable diseases
measles
- contagious from 4 days before and 4 days after rash onset
383
measles sign and symptoms
- high fever
- cough, coryza (nasal inflammation), conjunctivitis (swollen, red eyes)
- koplik spots (white spots in the inner cheek)
384
describe the measles rash
- virus spreads through the bloodstream and causes a characteristic rash
- maculopapular rash begins at face, then trunk and extremities
385
what are some complications of measles
- viral pneumonia
- encephalitis
- often secondary infections lead to ear infections and bacterial pneumonia
386
what does measles prevention - MMR vaccine
- prevents measles, mumps, and rubella
- MMR vaccine is a live attenuated vaccine
- 2 dose vaccine is 97% effective
387
what virus causes rubella
the rubella virus
- enveloped virus
388
what is rubella's epidemiology
- humans are the reservoir
- transmission: airborne respiratory droplet nuclei and vertical transmission (mother to baby)
- groups at risk:
- occurs most often in school-aged children;
mild
- most severe in neonates -> congenital rubella
syndrome
389
what are rubella's signs and symptoms in children
- widespread faint, shorter-lived red macular rash
- not associated with koplik spots
- lymphadenopathy (swollen, inflamed lymph nodes)
390
true or false rubella is an example of a teratogen? define teratogen
true
- teratogen = something that disrupts normal development of the embryo
391
what are the most common infections associated with congenital anomalies
TORCHeS
- Toxoplasmosis
- "Other" infections (HIV, syphilis, VZV)
- Rubella
- CMV
- Herpes simplex virus
392
what is congenital rubella syndrome
- rubella virus crosses the placenta in first trimester, high risk for
- stillborn
- spontaneous abortion (aka miscarriage)
- congenital rubella syndrome birth defects:
deafness, heart defects, brain damage
393
varicella (chickenpox) is caused by
varicella zoster virus (VZV)
- enveloped virus
- belongs to herperviridae family
394
all herpes viruses have
- double-stranded DNA genomes
- enveloped
395
true or false - all herpesviruses establish latency
true
396
what are latent infections
remain inactive inside infected cells as episomes (circular viral genome molecules outside of the host chromosome)
- reactivation causes recurrence of the disease
397
latency is maintained by
T cell-mediated immunity
398
what type of agents are not effective against latent viruses
antiviral agents
399
are herpe infections curable
no
400
what is in the herpesviridae family
- herpes simplex virus 1 and 2
- varicella-zoster virus (VZV)
- epstein barr virus
- cytomegalovirus (CMV)
401
define primary infection
first experience with the virus
402
define latent infection
persistence of the virus in a non-replicating state
403
reactivated/recurrent infection
virus coming out of latency and renewal of viral replication
404
define symptomatic infection
with clinical signs and symptoms
405
define asymptomatic infection
viral shedding without symptoms
406
with varicella-zoster virus (VZV) what is the primary acute infection
chickenpox (aka herpes varicella)
407
with VZV what is the recurrent infection
shingles (aka herpes zoster)
408
with varicella (chickenpox) the rash begins as
red papules and then progress to vesicles
409
scratching and rupturing the vesicles in varicella, can lead to serious secondary infection by
s. pyogenes or s. aureus
410
how is varicella transmitted
- respiratory droplet nuclei (ie airborne)
- direct skin contact
- vertical transmission (VZV is a teratogen)
- highly contagious
411
what group is at most risk for chickenpox
most severe in babies; congenital varicella syndrome -> birth defects; ~20-30% will die
412
VZV is latent in the ganglia and when reactivated what does it become
shingles
413
how does shingles differ from varicella
- rash pattern (along dermatome)
- pain level
- duration (can last up to 1 month)
414
a person with shingles lesions is contagious and can transmit the virus to a nonimmune contact. the newly infected individual would develop...
- shingles
- pneumonia
- chickenpox
- measles
- rubella
chickenpox
415
describe the varicella vaccine
- live attenuated vaccine
- often combined with MMR
416
describe shingles vaccine
- recombinant subunit vaccine
- advised for adults over the age of 50
