MICR 2123 Exam 4

What is a pathogen?

A microbial organism that causes disease.

What is a commensal organism?

Harmless bacteria that are on our body and can only cause disease if they are accidentally introduced into deeper tissues.

Describe the human microbiome.

All the microbes in or on our body.

Name the body sites that are most hospitable to bacteria and have their own microbiomes.

Mouth, Respiratory tract, Stomach, Intestines (most hospitable), Skin (not very hospitable), eye (not very hospitable), genitourinary

Why is skin difficult for microbes to colonize?

Because it's dry, salty, acidic, and has protective oils.

Associate Propionibacterium acnes with acne.

It breaks down skin oil which causes inflammation, also known as, acne.

What are factors that make the mouth hospitable to bacteria?

Nutrients/Food, Epithelial debris, secretions, and it is warm and moist.

How is Helicobacter Pylori associated with stomach ulcers?

It causes stomach ulcers.

What are the mucociliary escalator components and what is it's function?

Along the lining of the lungs and parts of the lungs are cells with cilia lining them. The cilia containing cells have mucus on them and as the cilia constantly beat up they propel the mucus up and out of the lungs slowly. If we inhale anything it sticks to the mucus and is pushed up which keeps our lungs clear of bacteria and allows for proper function.

What bodily location contains the most resident bacteria?

The intestine (gut microbiome)

What factors influence the composition of the gut microbiota?

Food (biggest One), Sleep, Stress, Other diseases, and medication

What is dysbiosis?

An imbalance in the proportions of different commensal microbes in the gut.

What is a probiotic?

Living bacteria that are ingested and help to restore a healthy microbial population.

What is fecal microbial transplants?

Microbiotal species taken from a healthy individual usually from a fecal sample, then purified, then transplanted to a person or host with dysbiosis to try to correct it.

How do scientists assess the composition of a microbial community? What is the most commonly used method?

sequencing of the 16s rDNA that encodes the small ribosomal subunits of rna. By looking at the sequence of the DNA you are able to identify the species present.

What is an opportunistic pathogen?

A pathogen that typically only infects individuals who are already ill or immunocompromised.

What are 3 physical barriers to microbes entering the body?

Skin and Mucous membrane

physical and chemical barriers vs. innate immune functions vs. adaptive immune functions

chemicals involve chemicals. physical are like fences. innate are like a police force always checking for suspicious activity. adaptive always targeted.

What are the chemical barriers ?

Lysozyme, Peroxidase, Iron-binding proteins, Defensins

What is the function of the chemical barriers?

Lysozyme: enzyme that cuts peptidoglycan. Peroxidase: creates reactive oxygen species that damage microbial cells. Iron-binding proteins: deprive pathogens of iron. Defensins: small peptides made from mucous membranes that poke holes in bacterial membranes and let them leak out.

Describe pathogen associated molecular patterns.

Patterns of molecules that are associated with pathogens.

What phagocytic cells recognize and engulf pathogens to destroy them?

Neutrophils (white blood cells), Macrophages, and dendritic cells.

Describe the process of phagocytosis. How does it kill microbes?

A bacterium is taken into a phagosome and then the phagosome is fused with a lysosome and the lysosome contains chemicals and enzymes to kill or degrade the bacterium.

What is in the lysosome?

enzymes mostly.

Describe pattern recognition receptors in terms of their function.

molecules that detects PAMPS. Look for suspicious activity.

Name two classes of PRR's.

TLR's (on cell surface) NLR's (inside cell)

What are the 4 cardinal signs of inflammation (not including loss of function)?

Heat, Redness, Pain, Swelling

What is a cytokine and what are common functions of them?

Chemical messengers secreted by cells to signal to other cells. In a way call for back up and also activate other cells to make them participate.

Which bacteria are susceptible to damage by the MAC?

Gram-Negative bacteria

Humoral Immunity vs. Cell Mediated Immunity

Humoral: Happens within fluid. Cell Mediated: Requires cells.

Identify T-Cells and B-Cells as lymphocytes (part of adaptive immunity).

Both are lymphocytes that are part of adaptive immune system.

What are the primary and secondary lymphoid organs?

primary: Thymus (where t cells develop) bone marrow (b cells) Secondary: lymphnodes, appendix, adenoids, tonsils, and spleen

What is an antigen?

Pathogen that elicits an immune response.

What is an epitope?

A smaller part of an antigen. The molecular patterns that interact with the antibody or t cell receptor.

What are the cellular interactions that permit massive antibody production to an antigen?

A B cell sees an antigen (foreign invader) then thinks if the antibodies react that it can be activated must react with the t cell then say hey ive seen this antigen then the t cell has to say yes and that the b cell can interact and then it will differentiate into a plasma cell and make a ton of antibodies.

What is the structure and major functions of antibodies?

A Y

heavy chains, light chains, variable region, constant region.

Being able to neutralize toxins and bacterial cells.

What is the genetic process by which antibody diversity is generated from relatively few genes?

Pick and choose gene segments and put them into different combinations and then further mutate them.

How do antibodies specifically interact with antigens/ epitopes?

They have regions at the variable region with different amino acids that come off and they physically interact with a particular antigen that matches the pattern of amino acids on the antibody

Physical interactions at the tips of the y.

How do B cells undergo negative selection to avoid auto immunity?

Make sure B cells don't make antibodies to the things in our own bodies. Tested in the bone marrow and if they react to things in our own body they are destroyed.

B cells vs. plasma cells (with respect to antibody production)

Plasma comes from B cells, but they are designed to manufacture antibodies.

B cells display antibodies on their surface and plasma cells make and secrete antibodies.

What are memory B cells and what is their relationship to a secondary antibody response?

Memory B cells circulate around to make more antibodies once one antibody has been made. Much faster than a primary antibody response. Secondary antibody response helps you to not get the disease.

What is the function of antigen presenting cells?

To present antigens to T cells.

What is the function of the major histocompatability complex (with respect to antigen presentation)?

A molecule that is the platform used to hold the antigen being presented.

What is the function of T cell receptors and what do they interact with?

T cell receptors on the other side of the MHC molecule and sees the antigen that is being presented to see if they match up with it.

How is T cell diversity generated?

Generated by an analogous mechanism where different gene segments are recombined and then further mutated.

How do helper T cells function?

Helper t cells help other immune functions (required to let a b cell turn into a plasma cell)

How do Cytotoxic T cells function?

To kill infected cells (not the pathogen only the cells) used to fight viral infections.

How are T cells educated in the thymus to avoid autoimmunity?

They make sure the t cells interact weakly with the MHC (not at all or strongly is a no no) Educated so only weakly interacting t cells interact weakly with an MHC and then if there is an antigen it strengthens the interaction and activates the t cell.

How do cytotoxic T cells kill infected cells?

Release granzymes that poke holes in the membranes and induce cell death in the target cells.

What are superantigens and why can they be dangerous?

Strengthens the interaction by binding to the outside and bridging the MHC with a t cell receptor and due to a really strong reaction it sets off a huge immune response and could kill you

How do vaccines take advantage of adaptive immunity?

You expose the body to an antigen by a vaccine and a primary immune response occurs and the body makes antibodies to that antigen so if it sees that antigen again it will wipe out that pathogen right away

What is herd immunity?

when you have a transmissible disease and 2/3 of a community are vaccinated you will stop the transmission of the disease if it hits you and you've been vaccinated.

What is autoimmunity in terms of what the immune system recognizes or fails to recognize?

Effective immunity depends on the immune system to know what should and shouldn't be in your body. Autoimmunity is a failure of the immune system to distinguish between self and non-self and can severely harm a person when their own tissues are being attacked.

How does molecular mimicry of the u protein of streptococcus pyogenes lead to rheumatic fever?

A cardiac antigen that looks like the m protein antigen in S pyogenes (strepthroat) and sometimes a b cell will recognize the cardiac antigen and will attack your own heart tissue and cause rheumatic fever.

What is a parasite?

Anything that can dwell on or in another organism.

What organisms can be a parasite?

bacteria, protozoa, worms, eukaryotic or multicellular organisms.

Endoparasite vs. ectoparasite

endoparasites live inside the host and ectoparasites live outside the host or on the host.

Primary pathogen vs. opportunistic pathogen

Opportunistic pathogens cause disease ONLY when normal immunity is compromised (immunocompromised). Primary pathogens can even get a healthy person sick.

What is pathogenicity?

How well an organism can infect (infectivity) and how severe the infection is (virulence)

What is virulence and how is it related to LD50 or ID50 values?

How severe an infection is caused by a pathogen. The fewer organisms you need for infection or death the more virulent the organism is.

What is LD50?

Amount of pathogen you have to administer to animals to have half of them die (the lethal dose of 50% or LD50).

What is ID50?

When you have a pathogen that doesn't kill the host you use the ID50 value which is the amount of pathogen you have to administer to an animal to have half of them get an infection.

On the basis of infectious doses, accurately compare the virulence of two different pathogens.

The more virulent pathogen is the one that requires the smaller dose. Look for the smaller number.

What is a pathogen reservoir?

A host species where a pathogen lives in nature.

What is a pathogen vector?

A reservoir host that can transfer the pathogen

What is vertical pathogen transmission?

When a pathogen is passed from a parent to a child.

What is horizontal pathogen transmission?

From individual to individual.

What is accidental pathogen transmission?

A species that is not usually a part of the normal life cycle of the pathogen enters the life cycle of the pathogen and is accidentally infected.

What is immunopathogenesis?

When you become sick due to the immune response to something.

What is a virulence factor?

The things that bacteria or viruses produce that enable them to cause disease or be virulent.

What are the steps of pathogenesis once a pathogen enters the host body?

Enter into the body (passes through barriers).

Sticks to cells (adhere to the host cells).

Uses one or more virulence factors to escape from the immune system and allow them to replicate and get out of the host.

What is the function of adhesins?

Involved in the pathogen sticking to the host cells.

What are the mechanisms of bacterial exotoxins (diphtheria and cholera)?

Transfer a group onto a target enzyme within the host cell.

What are the bacterial organisms that make Diphtheria?

Corynebacterium diphtheriae

What are the bacterial organisms that make cholera?

Vibrio cholerae

What are diphtheria toxin targets in their host?

protein synthesis in the host cell.

What are cholera toxin targets in their host?

second messenger signaling in the host cell.

What class of bacteria make bacterial endotoxins? Where are they located?

LPS

Gram-Negative

outside of the bacterium

What is type II secretion and what is an organism that uses it?

Cholera and it has a piston that rams a folded protein out of the cell to secrete it

What is type III secretion and what is an organism that uses it?

Salmonella, shigella, Yersinia and it looks like a tiny needle so an unfolded protein passes through that needle from one cell into another cell.

What is type IV secretion and what is an organism that uses it?

Bordetella pertussis and secretes things into the medium outside of the cell (looks more like a mating pilus)

What is type VI secretion and what is an organism that uses it?

Pseudomonas and it's a harpoon that's able to stick into a neighboring cell and deliver a pathogen.

What is an obligate intracellular pathogen?

Only can survive within host cells.

What is a facultative intracellular pathogen?

Can dwell inside or outside of host cells.

What are the mechanisms for immune evasion?

Phagosome escape, inhibition of phagosome-lysosome fusion, growth in the phagolysome, and inhibition of antigen presentation

What makes a compound an antibiotic?

Compound is able to kill or stop the growth of bacterial cells. Can't harm eukaryotic cells or the host.

What is the spectrum of activity?

How many different species a given antibiotic is effective against.

What is minimal inhibitory concentration (MIC)?

How much of an antibiotic you need in order to stop bacterial growth.

How do you compare the potency of different antimicrobial compounds based on their MIC value?

The lower the value is the more potent one.

Lower value=more potent

higher value=less potent

What is the target of B lactam antibiotics?

The bacterial peptidoglycan cell wall.

What are the targets for antibiotics?

Cell wall, cell membrane, DNA synthesis, RNA synthesis, Protein synthesis

What are the two B-lactam antibiotics?

Penicillin's and cephalosporins are beta lactam antibiotics.

What are bactericidal antibiotics with respect to their effect on bacterial growth and survival?

They kill bacteria.

What is bacteriostatic antibiotics with respect to their effect on bacterial growth and survival?

They stop the growth of bacteria.

What are the three major mechanisms of antibiotic resistance?

Antibiotic modification, antibiotic efflux, and destruction.

What is the modification of antibiotic targets as a mechanism of antibiotic resistance?

Modifies the target of the antibiotic so that the antibiotic can no longer effect its target.

How does overuse of antibiotics relate to antibiotic selection and the emergence of antibiotic resistant pathogens?

Overusing antibiotics you are always selecting for the most antibiotic resistant bacteria and increasing the chance that we have antibiotic resistant bacteria in our immediate environment and increasing the risk of infection with antibiotic resistant bacteria making infections harder to treat.

What are persistor cells and distinguish persistence from resistance?

The tiny population of non-growing cells within a larger population of growing cells. When introduced to an antibiotic the growing cells die and the non-growing cells survive (not grow) and if the antibiotic leaves then the non-growing cells can grow and restart the population. (The resulting population will still be antibiotic sensitive, but it didn't get wiped out thanks to the persistor cells)

Why are fungal infections more difficult to treat than bacterial infections?

Fungal cells are eukaryotes so its harder to find compounds that can tell the difference and leave our cells alone and only harm the fungal cells. However, fungal cells have a cell wall so most compounds now a days target the fungal cell wall.

Which of the following is a defensive enzyme made by the human body that specifically cleaves the disaccharide backbone of peptidoglycan?

a. Lysozyme

b. Peroxidase

c. Lactoferrin

d. Interleukin 6

Lysozyme