Exam 3 Flashcards
what does a vaccine contain
dead or weakened or subunits of pathogens that stimulate the immune system
what do vaccines produce
Abs or CTL
- exactly like it would if you were exposed to the disease
after getting vaccinated, what do you develop
immunity to that disease
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
CD4+ T cells
CD4+ T cells recognize antigen presented on….
MHC 2
in order to present on MHC 2, antigens must be processed via….
lytic enzymes in the phagolysome
are antigens on MHC 2 exogenous or endogenous
exogenous
memory CD4+ T and B cells are generated when…
- APCs engulf antigens and present peptides to CD4+ T cells
- B cells engulf antigens and become activated when they receive T cell help
memory CD4+ T and B cells are produced efficiently even when
the microbe has not infected an APC
true or false, in order to generate CTL, APCs need to be infected by the microbe
true
memory CD8+ T cells are generated when…
when an APC becomes infected
- digests the antigen into peptides and presents it to CD8+ T cells (which receive T cell help)
memory CD8+ T cells are produced when
the microbe infects an APC
what are the two major categories of vaccines
- attenuated vaccines
- inactivated vaccines
what are attenuated vaccines
they use a live/active but weakened form of the pathogen
- uses whole bacterial cells or viruses as the antigen
can attenuated vaccines cause diseases
no
what are inactivated vaccines
they are unable to replicate
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
no risk of causing infectious disease
what are considered safer, inactivated vaccines or live attenuated vaccines
inactivated vaccines
do inactivated vaccines need boosters
yes
inactivated vaccines come with a reduced ____ of the vaccine
effectiveness
live attenuated vaccines production is usually done with
meticulous quality checks ensuring their safety
for live attenuated vaccines who should be careful with those types of vaccines
pregnant women and immunocompromised people
what are the four types of inactivated vaccines
- 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
what do subunit vaccines often require
adjuvant = a chemical that enhances antigenicity by stimulating dendritic cells and macrophages
- boosts immune response
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
would a vaccine that contains bacterial capsule (ie a polysaccharide vaccine - T-independent) elicit a robust response in young children
no
are polysaccharides T-independent antigens or T-dependent antigens
T-independent antigens
polysaccharides (T-ind antigens) need to be ____ to a protein (T-depend antigens) to enhance their ___ in young children
conjugated; antigenicity
do T-independent antigens bind to other T-independent antigens
no
- T-independent antigens can only bind to other T-dependent antigens
do conjugate vaccines require T-cell help
no
the preparation of conjugates makes T-independent antigens into
T-dependent antigens
vaccination confers ___ ___ to the individual vaccinated
active immunity
true or false - some people believe that naturally acquired immunity is better than the immunity provided by vaccines
true
what are some usual side effects of vaccines
- local soreness at the injection site
- minor fever
- malaise
- feeling tired
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
what is microbiota
the microorganisms that normally colonize various sites on/within the body without causing disease
what are two different types of microbiota
- resident microbiota = inhabit sites for extended periods
- transient microbiota = inhabit temporarily for days, weeks, or months and then disappear
what does colonization mean
the ability of a microbe to stay affixed to a body surface and replicate
where do these microbiota colonize
nose, mouth, throat, skin, LI, urethra, and vagina
where in the body is free of microbes (sterile)
blood, CSF, and internal organs
part of our first line of defense against infection competitively exclude
pathogens
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
what does microbiota aid in
- digestion
- vitamin production
- drug metabolism
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.)
by age three, a child’s microbiome looks a lot like
an adult’s
- and becomes much more stable
microbiota changes in response to events like
- illness
- disease
- antibiotic treatment
- fever
- stress
- injury
- changes in diet
what is a pathogen
any bacterium, virus, fungus, protozoan, or helminth that causes disease
what is pathogenicity
the ability of an organism to cause disease
what are types of pathogenicity
- genetic makeup of the pathogen
- location in/on the host’s body
- host immune response
what can true (“primary”) pathogens cause
they can cause disease in a host regardless of the host’s resident microbiota or immune system
are true pathogens ever part of the normal microbiota
no
what do opportunistic pathogens cause
disease only under opportunistic conditions, ie situations that compromise the host’s defenses
opportunistic pathogens can be members of
normal microbiota or common in the environment
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
- immune suppression (chemotherapy, organ
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
what is c. diff resistant to
a lot of antibiotics
what does lactobacillus do in the vagina
it’s a bacterium in the vagina that suppresses yeast growth
can someone be infected but not have an infectious disease
yes
what is an infection
a successful colonization and multiplication of microorganisms within a host with or without the manifestation of disease
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
what does virulence mean
the degree or severity of disease
pathogens differ in their ___ of virulence
degree
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
how can virulence be measured
by LD50 (lethal dose 50)
- the number of microbes that kills 50% of an experimental group of animal hosts
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
what does infectious dose (ID) mean
the minimum number of microbes required to be taken in by the body to cause infection
what does ID50 mean
the number of microbes that will cause infection in approx. 50% of an experimental group of hosts
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
what are the four stages of pathogensis
- adhesion = to skin or mucosa
- invasion = through epithelium and immune evasion
- infection = colonization and growth
- tissue damage, disease
between what two stages of pathogenesis do toxins or host immune response occurs
between infection and tissue damage - disease
what are the six portals of entry
- fecal-oral = through mucosal surfaces of GI tract
- respiratory = through mucosal surfaces of respiratory tract
- transplacental = through the placenta to infect a fetus
- skin = through epithelial surfaces
- urogenital = through mucosal surfaces of genital and urinary tracts
- parenteral = through injection into the bloodstream (ex: insect bites or needle sticks)
what cellular structures help pathogens adhere
- fimbriae adhesions
- cell wall adhesions
- glycocalyx (slime and capsular polysaccharides)
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
- acquire changes in the genes for surface antigens that
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
what are four ways that intracellular bacteria survive within phagocytes
- by preventing fusion of the lysosome with the phagosome
- by escaping from the phagosome before the lysosome fuses
- by preventing acidification of the phagosome
- by resisting killing by lysosomal chemicals
once a pathogen is in, attached and evade the immune response, what does it do
it replicates and grows
true or false - with colonization and growth, new organisms must compete with established organisms for nutrients and space
true
what does localized mean
when pathogens grow locally at the site of the invasion
what does systemic mean
when pathogens may spread throughout the body
cellular damage can be a direct result of ___ or indirect via ___
- pathogen (such as toxin production)
- immune response
toxins may be transported by ___ or ____
blood; lymph
what are the two general types of toxins
- exotoxins
- endotoxins
what are exotoxins
proteins produced by pathogenic bacteria (gram positive and gram negative) and secreted
what are endotoxins
the lipid A portions of LPS that are part of the outer membrane of the cell wall of gram negative bacteria
when are endotoxins liberated
when the bacteria die and the cell wall breaks apart
how do you name exotoxins
- by types of cell affected
- by associated disease
- by bacterium producing it
what are the three major modes of exotoxins’ action
- cytolytic toxins
- AB toxins
- superantigen toxins
what does cytolytic toxins do
they work by disrupting cytoplasmic membrane integrity, causing cell lysis and death
- toxins that lyse RBCs are called hemolysins
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
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
where do bacteria get their exotoxin genes
horizontal gene transfer
- most genes for exotoxins are carried on plasmids or phages
how does the body fight exotoxins
the body makes Abs (antitoxins) -> provide immunity
how are exotoxins inactivated
by heat or chemical -> toxoid vaccine to stimulate antibody production
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
endotoxin - excessive release of cytokines from host is called
cytokine storm
what do endotoxin induce
inflammatory trauma throughout the entire body
- fever, shock, disseminated intravascular coagulation, and death
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
what is epidemiology
the science that underlies public health
what does epidemiology study
how disease originates and spreads throughout a population
what is the goal of epidemiology
to prevent outbreaks and contain them when they do occur
what are four patterns of infectious disease occurrence
- endemic = disease consistently present (often at low level) in a population
- sporadic = when occasional cases are reported at irregular intervals
- epidemic = occurrence of more cases of disease than expected in a given area over a particular period of time (“outbreak”)
- pandemic = an epidemic occurring on several continents and usually affecting an exceptionally high proportion of the global population
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
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
what does mortality rate mean
incidence of death due to a disease during a particular time period
what does case fatality rate mean
mortality rate/incidence rate
are all infectious diseases contagious
no
true or false - an infectious disease may or may not be communicable
true
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
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
which stage is an infection transmissible
transmissible during any of the stages depending on the pathogen
what are the two types of contact transmission
- direct
- skin-skin
- mucous-mucous (sexually transmitted)
- across placenta
- through breast milk - indirect
- droplets = close range (ie respiratory droplets) inhaled by someone close by)
- fomites = inanimate objects that transmit pathogens (ie doorknobs)
what are three types of vehicle transmission
- air-borne
- aerosols
- droplet nuclei inhaled by those over a long distance - food-borne
- water-borne
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)
what is vector transmission
- living organisms that can carry pathogens
- arthropods: insects (flies, mosquitos) and arachnids (mites, ticks, and spiders)
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
what are three types of reservoir
- human reservoir
- animal reservoir
- non-living reservoir
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
what is a human reservoir capable of transmitting
a pathogen who do not present signs or symptoms of disease is an asymptomatic carrier
what are zoonoses
diseases that can be transmitted from animals to humans
true or false - 75% of all emerging infectious disease are zoonotic
true
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
how are zoonotic diseases acquired
through various routes
in zoonoses animals are the ___ host
definitive
in zoonoses humans are typically __-__ host
dead-end
what are three types of durations of the disease
- acute disease = symptoms develop rapidly (strep throat)
- chronic disease = symptoms develop gradually over months, years, or lifetime and are slow to resolve (hepatitis C)
- 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)
are latent organisms ever eliminated
no
which bacteria are gram positive
- staphylococcus
- streptococcus
- bacillus
- clostridium
- corynebacterium
which bacteria are atypical
- mycoplasma (no cell wall)
- mycobacterium (acid-fast cell wall)
- spirochetes (thin cell wall) includes Treponema and Borrelia
what is the most virulent staphylococcal species
s. aureus
what does s. aureus produce
- impetigo
- TSS
- SSS
- food poisoning
- folliculitis, carbuncle, and furuncle
what kind of virulence does s. epidermidis (CoNS) have
low virulence
true or false - s. epidermidis is the normal microbiota of the skin
true
what does s. epidermidis cause
opportunistic infections
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
is s. aureus coag positive or negative
positive
- have solid at the bottom
is s. epidermidis coag positive or negative
negative
- going to be liquid
different types of hemolysis on blood agar
- B-hemolysis = complete hemolysis (halo)
- alpha-hemolysis = incomplete hemolysis -> green pigment
- y-hemolysis = no hemolysis (clear)
what type of hemolysis is s. aureus
b-hemolytic
- produces hemolysins called staphylolysins
what type of hemolysis is s. epidermidis
y-hemolytic
what does mannitol salt agar inhibit
the growth of many organisms EXCEPT staphylococci which is halotolerant (ie facultative halophile)
organisms that ferment mannitol are detected by a change in the
pH indicator from red to yellow
what type of media is mannitol-salt agar
- selective
- differential
- general purpose
- enriched
- selective and differential
selective and differential
how do we distinguish staphylococcus from streptococcus
staphylococci produce catalase
what does catalase break down
hydrogen peroxide (H2O2) produced during oxidative metabolism
- bubbles will appear
do streptococci produce catalase
no
how is s. aureus resistant to penicillin
because it produces beta lactamase (penicillinase) and thus is resistant to penicillins and cephalosporins
do streptococci produce beta lactamase
no most strepc don’t, therefore remain sensitive to beta lactam antibiotics
true or false - s. epidermidis are relatively avirulent
true
what helps s. epidermidis adhere to devices
the production of slime layer because it forms biofilms on the devices (catheters, shunts, prosthetic joints, etc)
when does s. epidermidis become opportunistic infections
when introduced into deeper tissues or a normally sterile site
when are opportunistic infections of s. epidermidis usually acquired
during a hospital stay
what is the major cause of hospital acquired infections
s. epidermidis
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
is s. aureus very contagious
yes
who are the main reservoirs for s. auerus
humans
about 30% of healthy adults are ___ __ for s. aureus
nasal carriers
what are the three types of transmission of s. aureus
- direct skin to skin contact
- indirect contact via fomites
- ingestion of contaminated food
s. aureus has a high tolerance to
salt and desiccation (drying conditions)
what are the major virulence factors of s. aureus
- capsule
- catalase
- exotoxins: enterotoxin, TSST-1, and exfoliative toxin
- coagulase
- staphylolysin
- leukocidin
- protein A
- hyaluronidase
what are virulence factors
they can be genetic, biochemical, or structural features that enable an organism to produce disease
pathogenesis may depends on
a single or multiple virulence factors
how do strains of s. aureus differ
by which virulence factors they produce
- some strains are more virulent because they make more virulence factors
for most disease caused by s. aureus, pathogenesis depends on the combined actions of
several virulence factors
what does catalase do
neutralizes hydrogen peroxide
- a type of ROS
- counteracts phagocytes’ oxidative killing
what does capsule do
inhibits phagocytosis
- composed of polysacchs
which virulence factors are exotoxins that were produced by s. aureus
- staphylolysin
- enterotoxin
- toxic shock syndrome toxin 1 (TSST-1)
- exfoliative toxin