Microbiology: Pathogens and Pathogenicity/Immunology
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An infection is?
colonized by microbe but may not be interfering with normal body function.
A disease is?
colonized by microbe that is harming body functions.
A situation in which both organisms benefits from the symbiotic relationship.
A situation in which one organism does not benefit and the other may or may not benefit from the symbiotic relationship.
A situation in which one organism benefits and the other is harmed from the symbiotic relationship.
What is resident flora?
Bacteria that is always on or in the host.
What is transient flora?
Bacteria that comes and goes.
What is an opportunistic pathogen?
A bacteria (resident or transient) that gets put somewhere where it is not supposed to be and thus creates damage.
What is etiology?
The study of finding the cause and microbe associated with a disease.
What is an etiologic agent?
The microbe that is associated with a particular disease.
What are Koch's Postulates?
- 1) Same organism present in every cause of the disease.
- 2) Must be able to culture the organism.
- 3) Inoculate into a susceptible host and host must develop the same symptoms as previously infected hosts.
- 4) Organism is the same as the original isolate.
How do you make a bad bug?
- 1) Gain entry into the host
- 2) Adhere
- 3) Virulence Factors
- 4) Evade Host Defense
How can the organism gain entry into the host?
They can gain entry through the skin, respiratory tract, urinary tract, GI tract, and genital tract.
What are the defenses that the skin provide?
The skin is very thick and has a keratinized layer that makes it waterproof. Sweat also helps because it is salty and acidic. If there is an abrasion then the bacteria will be able to enter the host.
How do the bacteria adhere?
- 1) Adhesion factors (adhesion ligands)
- 2) Pili/Fimbrae
- 3) Capsule (glucose polymers -> dextran)
What are virulence factors?
Features that increase the ability of the microorganism to infect and cause disease. These factors are not meant to cause disease but it gives them a home and a means of transmission.
What are the phagocytes?
macrophages and neutrophils.
What is the purpose of the phagocytes?
To engulf an offending organism. If the organism has a capsule then it makes it difficult to engulf.
What is incomplete phagocytosis?
The bacteria is engulfed but it blocks the lysosome from dissolving it so it can multiply in the macrophage and neutrophil and the immune system won't attack.
What are the enzymes that degrade the tissue so that the microbe can get deeper inside for protection?
coagulase and kinase
Pili and fimbrae...
help with adherence but also make it very difficult for a white blood cell to engulf the organism.
What is a fomite?
An inanimate object that transfers bacteria.
What is an exotoxin?
Toxins that are produced and secreted by the organism.
What is an endotoxin?
Toxins that are physically part of the organism.
What are the exotoxins?
Haemolysins, Enterotoxins, Cytotoxins, and Neurotoxins.
Exotoxin genes are....
located on the chromosome or plasmids. The plasmids can transfer the plasmid via conjugation.
What are the endotoxins?
Mainly found in the gram negative bacteria because of their lipopolysaccharide membrane. When this membrane breaks down it leads to fever due to a change in the set rate of the hypothalamus.
What is innate immunity?
A type of immunity that is provided to the organism by evolution. You have this type of immunity from birth. It is non-specific and will pretty much attack anything foreign that enters into the body.
What is the first line of defense against disease?
The skin and the mucous membranes.
What is the second line of defense against disease?
- Blood cells
- * neutrophils, basophils, eosinophils, and monocytes.
- part of the granulocytes
- highly phagocytic
- first responders
- attracted to the bacteria via a chemical (chemotaxis)
- the best and most abundant phagocytes
- attracted by chemotaxis
- used to clean up the tissue and last bit of bacteria that the neutrophils left behind.
- able to produce toxins against eukaryotic pathogens
- slightly phagocytic
- able to trigger inflammation
- responsible for producing histamine and releasing it which recruits white blood cells
What is inflammation?
It is usually a localized response in which cells release a chemical known as chemokine. Chemokine is a communication molecule.
- a systemic response
- stimulated by a chemical known as a pyrogen which act to reset the hypothalamus set point.
- not always a bad thing because it can help to kill of microbes since they are not accustomed to living at higher temperatures.
- an immune stimulant
What is complement?
a group of about 20-25 proteins found in the blood that are targeted specifically against bacteria, but they are not active all of the time.
What are the three goals of the complement system?
- 1) Trigger inflammation
- 2) Kill the bacteria (cell lysis)
- 3) Opsonization ( some of the proteins will bind to the bacteria which will aid in white blood cell phagocytosis)
Acquired/Adaptive immunity is...
specific and learned
How is adaptive/acquired immunity learned?
natural exposure (everyday occurrences and run ins with bacteria and viruses, breast milk, and from the mother at birth) and intentional exposure (vaccinations).
What are the components of humoural immunity?
B-lymphocytes (B-cells) and antibodies that the B-cells produce.
What are the components of cell mediated immunity?
T-lymphocytes (T-cells) and NK cells (natural killer cells).
What are the five main immunoglobulin classes?
- 1) IgG (most abundant and used for long term immunity)
- 2) IgM (pentamer and linked by J-chain; used in short term immunity)
- 3) IgE (surface of basophils->receptor proteins)
- 4) IgD (surface of immature B-Cells-> receptor proteins)
- 5) IgA (monomer, dimer or trimer; usually found in mucous membranes)
Explain Antibody Production
Stem Cell -> Pre-B cells -> migrate to lymphatics -> Blast Cells (immature B-cells) -> antibody exposure -> clonal selection-> binding of specific epitope -> clonal expansion-> differentiation-> mature B-Cell.
What are the two types of mature B-Cell?
- Plasma cells (used for short term immunity; IgM producer; antibody protein producer)
- Memory B-Cells (long term; IgG producer)
What is the anamnestic response?
The body making antibodies in response to an antigen.
What does immunogenic mean?
How good is the antigen at stimulating the immune response.
Explain the latent period
This is where B-Cell activation occurs and it usually takes about 7-14 days.
Explain the exponential phase
The antibody levels rise and IgM is produced.
Explain the declining phase
The plasma cells die off and memory cells increase along with the production of IgG.
Explain cell-mediated immunity (T-cell production).
Hematopoietic stem cells make non-active T-Cells -> T-cells migrate from bone marrow to the thymus gland or lymphatic system -> antigens activate -> mature T cells move to circulation or the lymph system.
What are the specialized T-Cells?
T-Helper, T-Suppressor, Cytotoxic T, and Hypersensitivity T.
Explain the T-dependent antigen response.
The macrophage engulfs the microbe and begins to digest it. Then it displays the pathogen peptide (antigen presentation). The antigen presentation is recognized by a helper T-Cell and they interact activating the T-helper cell. It begins to activate proteins like interleukin 1 and this acts as an attractant to the blast cells. The helper-T activates the B-Cell and also produces a B-Cell growth factor that stimulates B-cell reproduction. B-Cells then differentiate into plasma cells.
What are Cytotoxic T Cells?
T-cells that are filled with granules of the protein perforin. If a cell is presenting antigen peptides, then the T-cell will bind to the cell membrane and release the perforin which basically pops the offending cell. T-cells have protection from the perforin so that they do not dissolve themselves that is known as protectin.
What are hypersensitivity T-Cells?
They are responsible for the allergy "delayed" response.
What are T-Suppressor cells?
They are cells that help to dampen the immune response. They also lead to the prevention of B-cell conversion to plasma cells.
What happens in an auto-immune disease?
The B-cells get confused because some of the normal cells present peptides that look like the same antigens they target. So this leads to the attack of normal cells thus leading to damage to healthy body tissue.
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