Week 7 Flashcards
The term gastroenteritis is applied to syndromes of diarrhea or vomiting that tend to involve _____ infection of the ___ or ____ of the ____
Non-inflammatory
Upper small bowel
Inflammatory
Colon
Who are more likely to get diarrhea, children or the elderly?
Children
What is the best way to prevent getting diarrhea?
Washing your hands!
What is the #1 anaerobic bacteria in the normal enteric microflora?
Bacteriodes fragilis
This plays an important role in the development of the immune system
What is the #1 facultative bacteria in the normal enteric microbiota?
E. Coli
What are the three different types of microbial virulence factors?
Toxins
Attachement
Invasiveness
What are the three different types of toxins that may cause diarrhea?
Neurotoxins
Enterotoxins
Cytotoxins
Neurotoxins are usually ingested as ____ that cause enteric symptoms
Preformed toxins
Neurotoxins have their effect on the ____ rather than directly on the intestine
Central autonomic nervous system
Name three bacterial species that produce neurotoxins
**clostridium botulinum
Bacillus cereus
Staphylococcus aureus
How do enterotoxins work?
Have a direct effect on the intestinal mucosa to cause fluid secretion
Cause an alteration in the metabolic activity of the intestinal epithelial cells
Results in an outpouring of electrolytes and fluid, primarily in the jejunum and upper ileum
Name four bacteria that produce enterotoxin
**vibrio cholerae
Non cholera vibrio spp.
E. Coli
Salmonella
What are cytotoxins responsible for? Where do they primarily affect? Cytotoxins often result in…
Responsible for mucosal destruction
Often results in inflammatory colitis
Happens almost exclusively in the colon
Generally referred to as dysentery
Name some species that produce cytotoxins
**shigella dysenteraie
S. Aureus
C. Perfringens
E. Coli
C. Difficile
Why is “attachment” a virulence factor?
They destroy the ability of cells to participate in normal secretion and absorption
Name four bacterial species that have attachment virulence factors
E. Coli
Giardia lamblia
Cryptosporidium
Isospora
Name some species that have the ability to invade the GI tract
Shigella
E. Coli
Vibrio
What percentage of food borne illnesses are due to bacteria and viruses? What about toxins and parasites? What species are the leading cause of bacterial food borne illnesses in the U.S?
84
16
Campylobacter jejuni and Salmonella
What foods are you most likely to get food poisoning from staphylococcus aureus?
Meats and milk products
Often because food handlers have a staph infection and get it in the food
Where is C. Perfringens likely to be found?
Lives in the soil but can grow on meats
When the spores germinate, it releases toxin
What foods are you most likely to get food poisoning from salmonella? How long does it take for onset?
Poultry, eggs, meats, milk, produce
Takes about 24 hours or longer because it must get to the small intestine.
True or false… Shigella does not survive well in the environment and must be transferred from person to person. It is an invasive pathogen and causes dysentery and fever
True
What food sources are you most likely to pick up shigella?
Produce
(But mostly fecal oral route)
Note that this bacteria is closely retaliated to E.coli, which is why it can pick up some E.coli genes
Where are you most likely to pick up campylobacter?
Water
Raw milk
Poultry
Pets
Note that this is one of the most common causes for food poisoning in the US
What is the most common vibrios (that is not vibrio cholera) to cause food poisoning? What is this bacteria associated with?
Vibrio parahaemolyticus
It is halophilic so it is associated with salt water and sea food (especially raw or uncooked seafood)
Describe bacillus cereus
Very widespread (you can find it about anywhere)
Spore forming
Found especially in rice, meat, and in dirt (on vegetables)
If you cook it, then cool it down, spores will form
Aeromonas Hydrophila is associated with…
Fresh water
Its like the fresh water version of vibrio parahaemolyticus
Vibrio cholera is usually found where?
If contaminated water. It doesn’t survive freely in water, it lives on microscopic crustations called coprapods. This means that it is easy to filter out vibrio cholera from water
What is SLT E.coli? What foods is it most likely to be present in?
It is E.coli that has taken up a shigella toxin gene
It is associated with hamburger because this meat has a lot more surface area for the microbe to grow on
Is listeria monocytogenes gram positive or gram negative? What foods is it most likely to be found in? This particular pathogen is especially detrimental to whom?
Gram positive rod.
Mostly found in milk products
Danger to fetuses because this bacteria can cross the uterus
What is a hysteria reaction?
Vomiting due to a psychological reason (such as watching someone else vomit).
This reaction occurs within minutes
What bacterial species has an incubation time of minutes-hours?
Bacillus cereus
Staphylococcus aureus
and chemicals, heavy metals, and shellfish toxins
What bacterial species have an incubation time of several hours?
Botulism
Clostridium perfringens
What bacterial species have an incubation time of a day or so?
*salmonella (sometimes quicker)
Shigella (sometimes longer) Vibrio parahaemolyticus Campylobacter Yersenia entercolitica Viruses
What organisms have an incubation time of days to weeks?
Clostridium difficile
Giardia
Amoeba
What is the best treatment for diarrhea no matter what the cause?
Fluid replacement
What fruit is recommended in a home fluid/electrolyte replacement? Why?
Bananas. Because of the potassium
True or false… antibiotics should be avoided in uncomplicated cases of non-typhoid salmonella
True
True or false… antibiotics should be avoided in cases of shigella and cholera
False.. they may be used
True or false… antibiotics have no value for food poisoning caused by staph, B. Cereus, and C perforingins
True
True or false… antibiotics is usually contraindicated in cases of SLT E. Coli and HUS
True
Which occurs first in B cell production, negative selection or positive selection?
Negative selection
Describe the 6 phases of B cells
1: repertoire assembly - generation of diverse B cells in bone marrow
2: negative selection - elimination of B cells with self-binding components
3: positive selection - promotion of a fraction of B cells that target appropriate antigen
4: searching for infection - recirculation of mature B cells
5: finding of infection - activation of B cells by pathogen derived antigens
6: Attacking infection - differentiation into plasma cells and memory cells
Name the three sources of antigen diversity
Genetic recombination
Junctional diversity
Somatic hypermutaion
Name the four effector functions of antibodies
Receptors (in B cells and granulocytes)
Neutralization
Opsonization
Signaling
Name the 5 different isotypes of the heavy chain of antibodies
IgG IgA IgM IgE IgD
True or false… both the heavy chain and light chain have proportionally small variable regions
False.. the heavy chain has a proportionally small variable region compared to the rest of the chain… the light chain, however, proportionally has a much larger variable region
True or false… the heavy chain does not bind antigen
False, it does bind antigen
True or false… a B cell is stuck producing the same isotype for the duration of its life
False… although the variable region is fixed for life, the B cell can undergo isotype switching
Cleavage of an IgG antibody will produce ___ and ___ fragments. Which is the convserved fragment with all antibodies?
Fc
Fab
Fc
True or false… different genes encode the heavy and light chains
True
Name the two isotypes of the light chain
K (kappa)
Lambda (lambda gets selected first)
Which, the heavy chains or light chains dictate the antibody class?
Heavy chain
Which antibodies have multimeric complexes?
IgM (pentameric)
IgA (dimeric)
**multimeric complexes involve the J-chain
Which antibody class can cross mucosal layers?
IgA
Which antibody is primarily involved in the sensitization of basophils?
IgD
Which antibody is primarily involved in the activation of the complement system?
IgM
Which antibody class is primarily involved in the sensitization of mast cells, but may also sensitize basophils?
IgE
Antibody variable regions bind antigen. What are the HV and CDR portions in the variable regions?
HV - hypervariable
CDR - complentarity-determining region
Antibodies bind antigen epitopes. Name four different types of epitopes antibodies may bind on an antigen
Terminal polysaccharide
Polysaccharide chain
Globular protein surface
Globular protein pocket
**note that antibodies may bind to epitopes in a linear fashion or a discontinuous fashion
What is the difference between an antigen and an epitope?
Antigen - a molecule recognized by a B cell or a T cell
Epitope - the region of an antigen bound by an antibody or MHC/TCR
True or false… a single antigen can be bound by multiple different antibodies
True. Because there are multiple epitopes on an antigen
How is it that antibody structure facilitates function?
Antibodies have flexibility in the hinge regions between the Fc and Fab regions that allow binding of epitopes that are physically spread
Where do B cells that are undergoing gene rearrangement reside?
Bone marrow
Once B cells have developed their antibody and are expressing their igM receptor, where do they reside? What occurs in this site?
In secondary lymphoid organs and in circulation
Somatic hypermutation and isotype switching
What chromosome is the heavy-chain locus located on?
Chromosome 14
What chromosome is the kappa light-chain locus found?
Chromosome 2
Which chromosome is the lambda light chain locus found?
Chromosome 22
In regards to genetic recombination of antibodies, the principle of allelic exclusion applies. What does this mean?
Only one functional chromosome.
I assume this means that the other chromosome is disintegrated much like barr-bodies and the X chromosome
Which chain of antibody will you find the HV (hypervariable region)?
Light chain
What does the RAG complex do?
Randomly pairs gene segments by splicing out the ‘junk’ DNA in between via hairpin loops
What is junctional diversity and how does it contribute to the variability of antibodies? What enzyme is involved?
TdT (terminal deoxynucleotidal transferase) will randomly insert nucleotides inbetween gene segments to increase diversity (by the random number and type of nucleotides)
Why is isotype switching permanent?
Usually isotypes are a permenant change (meaning once you switch isotypes from IgG to IgE, you CANT SWITCH BACK to IgG because DNA is actually removed… however you can still switch from IgE to another isotype, like IgA)
Isotype switching is permenant… except for ___ and ___, which are expressed first. Why are these two isotypes able to switch back and forth?
IgM
IgD
These are the first ones expressed and they are determined at the level of mRNA, not DNA.
Naive B cells express ___ and ___ until activated
IgM
IgD
(As receptors)
Describe how activation changes B cell immunoglobin fate
Mature naive B cells express IgM and IgD (high) receptors. They are activated by an APC (involves somatic hypermutation) They proliferate and differentiate into memory cells and antibody secreting plasma cells
Memory cells have ___ receptors
IgG
What is the order of class switching (isotype switching)
IgM/IgD —- IgG/IgA/IgE
Describe somatic hypermutation
It rapidly increases antibody affinity, and only occurs on the light chain on the HV (hyper mutation sites)
What is the difference between polyclonal and monoclonal?
Polyclonal - multiple antibodies targeted against the same antigen
Monoclonal - a single antibody targeted against a single antigen
