OSU Micro 4000 Final Exam Review

The ability to cause disease

pathogenicity

The degree of pathogenicity

virulence

To cause disease, a pathogen must (4 main things)

1. Gain access to the host

2. Adhere to host tissue

3. Penetrate or evade host defenses

4. Damage host tissue

Traits of a pathogen that help the pathogen to escape the immune responses and successfully establish an infection.

Virulence factors

Which of the following statements about adherence is true?

A) Most bacteria can adhere to any cell in the host.

B) Most bacterial adhesins are glycoproteins or lipoproteins.

C) The host cell receptors for bacterial adhesins are usually proteins.

D) Adhesins are always located on the bacterium's cell membrane.

B) Most bacterial adhesins are glycoproteins or lipoproteins.

A pathogen that is capable of antigenic variation can...

avoid host immune defenses

Exotoxins are bacterial _____________ secreted by a living bacterium into its surroundings, which circulate and cause damage to host tissues.

proteins

Two main ways to classify exotoxins:

1. Based on the area of the host that is affected (example: neurotoxins, enterotoxin, cytotoxin, etc.)

2. By structure and function (A-B toxins, membrane toxins, superantigen toxins)

What are the 3 broad categories for portals of entry?

1. Mucous Membranes

2. Skin

3. Parenteral

The pathway/ route the pathogen used to enter the host

Portals of entry

Regarding portals of entry, what 4 particular paths fall under the mucous membrane category?

1. Respiratory tract

2. Gastrointestinal tract

3. Genitourinary tract

4. Conjunctiva

Conjunctiva

Delicate membrane lining the eyelids and covering the eyeball, this is one mucous membrane path through which pathogens can invade.

How do some pathogens get in through the skin?

Through small openings, like hair follicle pores or sweat glands.

Parenteral route

Microbes deposited directly into tissues beneath the skin or directly into mucous membranes. This most often occurs through bites, cuts, and other wounds.

Getting cut by a rusty nail and contracting tetanus would be an example of which type of portal of entry?

Parenteral

If someone were to spit in your eye and then it becomes infected, which specific pathogenic portal of entry would that be called?

Conjunctiva, a type of mucous membrane entry path

Which is more common: a pathogen having a preferred portal of entry and only causing infection if it enters through that path, OR a pathogen causing infection regardless of how it enters?

Most pathogens have a preferred portal of entry and cause infections only if they enter through that specific portal of entry.

What are the 2 terms by which virulence can be quantitatively expressed?

ID50 and LD50

ID50

The infectious dose (either virulent particle number or concentration) needed to successfully establish infection in 50% of a sample population.

NOTE that the same pathogen can have different ID50s for particular portals of entry depending on the efficiency in which it can establish infection when entering through that route.

Suppose rabies virus has an ID50 of 100 viral particles through the parenteral route, and an ID50 of 1,000 through the skin route.

What exactly does this mean?

That for 50% of the population, the number of rabies virus particles needed to establish infection is 10 fewer when the virus enters through a wound than when simply contacting the skin.

In other words, the rabies virus, on average, could be said to be 10 times more efficient at establishing infection when it enters through a wound compared to simply contacting the skin.

Which quantitative virulence term is used to compare relative virulence under experimental conditions?

ID50

For ID 50, the __________ the ID50, the __________ the virulence

Lower; higher

LD50

Lethal dose that causes death of 50% of a sample population.

Which quantitative term is best for expressing the potency of a toxin?

LD50

What is the first necessary step for most pathogens in the path towards establishing infection?

Adherence (adhesion)

Adhesins

glycoproteins or lipoproteins found on the pathogen's surface that enable it to bind to host cells

List 4 examples of microbial structures which can serve as adhesins:

1. Glycocalyx structures like capsule and slime layer

2. Fimbriae

3. Pili

4. Flagella

Adhesins are almost always what two classes of biomolecules?

Glycoproteins or lipoproteins

The adhesin receptors on host cells are most often what type of biomolecule?

Carbohydrates

Adherence can involve ___________ formation and more complex interspecies interactions

Biofilm

What are the 4 main ways (or structures) by which microbes get passed host defenses?

1. Capsules

2. Cell wall components

3. Extracellular enzymes

4. Antigenic variation

1. What is the main way through which a capsule can be used by a microbe to get passed host defenses?

2. What can the host do about this?

1. By impairing phagocytosis by preventing a phagocyte from adhering to the microbe.

2. Hosts can produce antibodies against capsules

What are 3 important cell wall components which can help a microbe get passed host defenses? (Just the names, details on other cards)

1. M protein

2. Opa

3. Waxy lipids

M protein is found on cell surfaces and....

Fimbriae

What do M proteins do?

Mediates the attachment of the bacterium to the host, and helps resist phagocytosis.

Opa protein is in....

Cell wall

What do Opa proteins do?

Allow attachment to host cells in conjunction with fimbriae, helps the bacterium be brought into the host.

Waxy lipids may be found as a component of...

The cell wall

What is a main example of a waxy lipid found in bacterial cell walls?

Mycolic acid

How do waxy lipids help a bacteria get passed host defenses?

Resists digestion by phagocytic cells, and may even allow the bacteria to multiply inside of phagocytes.

What is the main functional difference between M proteins and waxy lipids regarding how these help bacteria get passed host defenses?

M proteins help resist being phagocytosed in the first place (makes it so the phagocyte can't even attach to the bacteria).

Waxy lipids on the other hand don't really stop the bacteria from being brought into a phagocyte, BUT it prevents the bacteria from being digested once inside the phagocyte.

What are the 3 main mechanisms of action through which extracellular enzymes may help a bacteria get passed host defenses?

1. The enzymes covers/ physically shields the bacteria, hiding it from the host immune system.

2. The enzymes aid in the spread of the pathogen throughout the body (such as helping them pass through capillary walls and stuff)

3. The enzymes may degrade antibodies.

List 5 extracellular enzymes bacteria use to avoid and evade the immune system:

1. Coagulases

2. Kinases

3. Hyaluronidase

4. Collagenase

5. IgA proteases

What do coagulases do and how do bacteria use these enzymes to their advantage

Coagulate fibrinogen to form blood cots. Helps isolate the bacteria from any influx of host immune cells and may protect the bacterium from phagocytosis.

What do Kinases do and how do bacteria use these enzymes to their advantage?

Digest fibrin blood clots. Blood clots are often formed by the host to help isolate infections. Kinases can break down these clots to help the pathogen spread throughout the body.

What do hyaluronidases do and how do bacteria use these enzymes to their advantage?

Digest the polysaccharide called "hyaluronic acid". Hyaluronic acid helps hold cells together in connective tissues of the host, so breaking it down helps the pathogen spread from its initial site of infection into other areas.

What do collagenases do and how do bacteria use these enzymes to their advantage?

Break down collagen, the major component of connective tissue. Breaking down connective tissue helps the pathogen spread.

IgA antibodies are present in...

Body secretions

Antigenic variation

Altering surface antigen to evade the adaptive immune response

Altering surface antigen to evade the adaptive immune system

Antigenic variation

What is a main reason flu vaccines have to be changed every year?

Antigenic variation

List 3 advantages of biofilms

1. Helps with adherence (to host and other microbes)

2. Helps resist phagocytosis

3. Extrapolymeric subtances (EPS) can shield antigens from detection.

Surface proteins produced by bacteria which rearrange actin filaments of the cytoskeleton of the host and causes membrane ruffling of host cell such to aid pathogen entry:

Invasins

Invasins

Surface proteins produced by bacteria that rearrange actin filaments of the cytoskeleton to aid in pathogen entry.

Invasins rearrange.....

Actin filaments of the cytoskeleton of the host cell.

Most bacteria that are captured by phagocytes are killed inside the phagolyosome, what neat evolutionary theme have some bacteria evolved which turns this problem into a solution?

Using phagocytic cells and structures of the phagosome as a part of their replication mechanism.

What are 3 ways some bacteria can use phagocytic cells and structures of the phagosome to their advantage?

1. Their replication mechanisms may be evolved for low pH, so the bacteria can use the low pH of the phagolysosome for their replication.

2. Some bacteria can escape the phagosome before it fuses with the lysosome, giving it free reign in the phagocyte to replicate in peace, hidden from the host immune system inside one of its own cells.

3. Some bacteria can prevent the phagosome from being able to fuse with the lysosome, providing the same advantage from #2 above (except in this scenario the bacteria is also inside of a vesicular compartment within the phagocyte).

Once inside the host cell, bacteria use __________ to propel themselves through host cytoplasm

Actin

Actin

thin filaments

bacterial actin (function in pathogenicity)

Component of the cytoplasmic matrix which can contract and release differentially within the bacterial cell to generate movement. This is used by bacteria to propel themselves through host cytoplasm regarding the establishment of an intracellular infection.

Cadherin

A member of a family of Ca2+-dependent proteins that mediates the attachment of one cell to another in animal tissues.

This protein can be used by bacteria to facilitate movement of bacterial cells between host cells, allowing for the spread of pathogens along a completely intracellular route (where the pathogen is also invisible to host defenses).

What are the 3 broad types of ways that bacterial pathogens cause damage to the host?

1. Using host nutrients

2. Direct damage to cells in the immediate vicinity

3. Producing toxins which are transported via blood and lymph and cause damage throughout the body

What is the main resource which pathogenic bacteria steal from the host?

Iron

Why is iron concentration low within human cells?

Due to a variety of iron binding proteins

Transferrin, lactoferrin, ferritin, and hemoglobin, are all...

Iron binding proteins

List the 4 main iron binding proteins found in human blood:

1. Transferrin

2. Lactoferrin

3. Ferritin

4. Hemoglobin

siderophores

proteins secreted by pathogens that bind iron more tightly than host cells

What are the 4 ways bacterial pathogens can cause direct damage which are limited to the immediate vicinity?

1. Get inside of a host cell and use its nutrients

2. Secrete harmful metabolic waste

3. Replicate inside of host cells, eventually causing them to rupture.

4. Damage host cell membranes in the process of getting into the host cell.

poisonous substance produced by certain microorganisms

toxins

What is often the primary factor contributing to pathogenic properties?

Toxins

Capacity to produce toxins is referred to as...

toxigenicity

Intoxications:

When the effects of pathogenesis are due to toxins and NOT the microbial growth itself.

Botulism (a type of food poisoning) is a good example of this. The microbes which cause botulism do not do so by "infecting"/ multiplying in the host, but rather they produce botulinum toxins (a class of neurotoxins) that cause paralysis and eventual death (since the diaphragm becomes unable to contract for breathing).

Botulism

a type of food poisoning cause by microbial production of botulinum toxins (neurotoxins)

Suppose a type of bacteria produces a gaseous compound that when inhaled causes damages the lungs and prevents the absorption of oxygen. This is an example of damage via...

Intoxications; effects of pathogenesis that is due to the toxin (not the microbial growth)

Suppose you consume a fruit that is a carrier of a pathogenic bacteria. Upon ingestion, this bacteria is NOT able to grow, but it does take a while to die off. During this time before it dies, it produces compounds that are absorbed, circulate, and cause damage to some tissue types throughout the body.

1. This is an example of damage via what?

2. During the time in which you have these harmful compounds circulating, it could be said that you have what?

1. Intoxications; effects of pathogenesis that are due to the toxin (not the microbial growth).

2. Toxemia; the presence of toxins in the blood

Toxemia

toxins in the blood

List 7 common ways that toxins may negatively impact the host:

1. Fever

2. Cardiovascular disturbances

3. Diarrhea

4. Shock (known as toxic shock syndrome aka TSS)

5. Inhibit protein synthesis

6. Destroy blood cells

7. Disrupt the nervous system

What are the 2 broad categories of toxins?

Exotoxins and endotoxins

Exotoxins

Produced inside some bacteria as part of their growth and metabolism and are secreted by the bacterium into the environment.

Endotoxins

The toxin is some physical component of the bacterial cells, which is released when the cells divide or when bacteria are destroyed.

Exotoxins are usually

proteins (typically soluble enzymes)

Exotoxins are often encoded on....

Plasmid or phage

Are exotoxin effects usually specific or non-specific

Highly specific

An exotoxin that causes signs and symptoms is referred to as a(n)...

Intoxicant

Antitoxins

antibodies against specific exotoxins

Toxoids

inactivated exotoxins (used in many vaccines).

Tetanus vaccines are an example of a __________

Toxoid

Exotoxins can be divided into 3 functional categories. These are...

1. A-B

2. Membrane disrupting

3. Superantigens

Which functional category constitutes a majority of exotoxins?

A-B

A-B toxin

Bacterial exotoxins consisting of two polypeptides. Part A inhibits protein synthesis of host, Part B binds to the host receptor.

Which part of an A-B toxin is the binding component?

B; B = Binding

What does the A component of an A-B exotoxin do?

A = Active component. Its what actually have the negative effect on the host cells (usually be inhibiting protein synthesis).

For an A-B toxin, what does the "A" and the "B" stand for?

A = active component

B = binding component

What are the 2 main ways membrane disrupting exotoxins work?

1. By forming pores in the host membrane

2. By disrupting phospholipids

What are two examples of membrane disrupting exotoxins?

Leukocidins and hemolysins

Leukocidins

A type of exotoxin which kills phagocytic leukocytes of the host immune system.

Hemolysins

A type of exotoxin which lyses red blood cells of the host.

Superantigens

cause an intense immune response due to release of cytokines from host cells

How do superantigens work? (the short version)

Combine with macrophages and stimulate T cell production, T cells release excessively high levels of cytokines. This leads to fever, nausea, vomiting, diarrhea, shock, and possibly death.

Endotoxins are usually part of the....

Outer portion of cell wall in gram negatives (lipid A)