Chapter 15- Microbial Mechanisms of Pathogenicity

Pathogenicity

Ability to cause disease by overcoming host defenses

Which of these eukaryotic molecules/structures can be responsible for movement of bacteria within host cells?

Actin molecules

Which of these substances are most important in the establishment of biofilms?

Adhesins

__________ are molecules on bacterial cell surfaces that enable them to adhere to the surface of host cells.

Adhesins

How can infection be prevented or controlled in regards to adherence?

Adhesins, receptors, or both, can altered to interfere with adherence.

Membrane ruffling

After making contact with the host cell, invasins of the microbe cause the appearance of the host cell plasma membrane to resemble the splash of a drop of liquid hitting a solid surface. Result of disruption in the cytoskeleton of the host cell. Microbe sinks into the ruffle and is engulfed by the cell.

What are the signs and symptoms of endotoxin production?

All endotoxins produce the same signs and symptoms, regardless of microorganism, although to varying degrees. Include chills, fevers, weakness, generalized aches, sometimes shock, and death. can cause miscarriages.

Which of the following virulence factors could directly prevent phagocytosis and/or phagocytic degradation? A. capsules B. M proteins C. waxy lipids D. all of the above E. none of the above

All of the above

Which of the following cell wall components do/does NOT contribute to virulence? A. Opa B. Mycolic acids C. Fimbriae D. M protein E. All of the listed choices contribute to virulence

All of the listed choices contribute to virulence.

Ergot

An alkaloid toxin that can cause hallucinations and is a natural source of LSD. Constricts capillaries and can cause gangrene of the limbs by preventing proper blood circulation in the body.

Fimbrae

An appendage on a bacterial cell used for attachment. Following attachment, host cells take in the bacterium.

Which of the following would be an example of an infection initiated via the parenteral route?

An individual contracts hepatitis B from an accidental stick with a contaminated needle.

Opa

An outer membrane protein that facilitates attachment. Bacteria that produce opa form opaque colonies on culture media. Following attachment, host cells take in the bacterium.

Antitoxins

Antibodies produced by the body that provide immunity to exotoxins

Botulism is caused by a proteinaceous exotoxin; therefore it can easily be prevented by

Boiling food prior to consumption.

How do membrane-disrupting toxins contribute to virulence?

By killing host cells, especially phagocytes, and by aiding the escape of bacteria from sacs within phagocytes (phagosomes) into the host cell's cytoplasm.

How do endotoxins exert their effects?

By stimulating macrophages to release cytokines in very high concentrations (toxic levels).

Sclerotia

Highly resistant, detachable portions of the mycelia of a fungus that contain the toxin ergot

Which of the following virulence factors is specifically involved in helping an organism to physically spread throughout the body?

Hyaluronidase

How does the gastrointestinal tract destroy most pathogens?

Hydrochloric acid and enzymes in the stomach or bile and enzymes in the small intestine

Gram-negative septic shock results from the following events. What is the second step?

LPS is released from gram-negative bacteria.

Endotoxins are also known as

Lipid A.

Lipid A

Lipid portion of LPS; is the actual endotoxin

Endotoxins

Located within the bacterial cells and are part of the outer portion of the cell wall of gram-negative bacteria. This outer membrane surrounding the peptidoglycan layer of the cell wall contains lipoproteins, phospholipids, and lipopolysaccharides (LPS), where the endotoxin is located.

Which of these viral cytopathic effects is most likely to be associated with the development of cancer?

Loss of contact inhibition

Which of these is a cell wall component that contributes to invasiveness?

M protein

Genotoxins

Made by some gram-negative bacteria; damage DNA by causing mutations, disrupting cell division, and may lead to cancer.

How is hyaluronidase used therapeutically?

May be mixed with a drug to promote the spread of the drug throughout a body tissue due to tis digestive action of spreading.

Which statement regarding endotoxins is true?

One consequence of endotoxins is the activation of blood-clotting proteins.

Hepatitis B virus transmitted by a finger-stick device enters the host via which portal of entry?

Parenteral

If a patient has a deep tissue infection as the result of an animal bite on the arm, the portal of entry is described as the __________.

Parenteral route

What are the components of A-B toxins?

Part A is the active (enzyme) component, part B is the binding component.

Endotoxins are

Part of the gram-negative cell wall.

Antigenic variation

Pathogens can alter their surface antigens. By the time the body mounts an immune system response against a pathogen, the pathogen has already altered its antigens and is unaffected by the antibodies

Portals of entry

Pathogens can gain entrance to the human body and other hosts through several avenues

Toxins

Poisonous substances that are produced by certain microorganisms and are often the primary factor contributing to pathogenic properties of microbes.

Which disease is correctly matched with the common portal of entry?

Poliomyelitis; mucous membranes of gastrointestinal tract

What happens when a microorganism does not enter the body through its preferred portal of entry?

Preferred portals of entry are a prerequisite to being able to cause disease. Gaining access through another portal may cause the disease to occur more mildly or not at all.

What is phagocytosis?

Process by which certain cells of the body engulf and destroy microbes

How does the human body counteract capsule defense?

Produce antibodies against the capsule, and when these antibodies are present on the capsule surface, encapsulated bacteria are easily destroyed by phagocytosis.

Which of the following does NOT contribute to a pathogen's invasiveness?

Toxins

Interferons

-alpha and beta interferons protect neighboring uninfected cells form viral infection in two ways: -inhibit synthesis of viral proteins and host cell proteins -kill virus-infected host cells by apoptosis (programmed cell death)

What are the effects of TNF on the body?

-damages the blood capillaries by increasing their permeability, leading to large amounts of fluid loss and a drop in blood pressure -low blood pressure has serious effects on the kidneys, lungs, and gastrointestinal tract

What are the cytopathic effects a virus can produce on cells?

-macromolecular synthesis within the host cell stops -host cell lysosomes are made to release their enzymes, resulting in destruction of intracellular contents and host cell death -inclusion bodies are found in the cytoplasm or nucleus of some infected cells -several adjacent infected cells fuse to form a syncytium -changes in the host cell's functions with no visible changes in the infected cells -induce antigenic changes on the surface of the infected cells that elicit a host antibody response against the infected cell, and thus they target the cell for destruction by the host's immune system -induce chromosomal changes in the host cell, leading to oncogenes (cancer-causing genes) to be contributed or activated by a virus -capable of causing cancer transform host cells, resulting in abnormal, spindle-shaped cells that do not recognize contact inhibition, leading to unregulated cell growth -host cells produce alpha and beta interferons. Viral infections induce cells to produce interferons while the host cell's DNA codes for them. Most viruses have mechanisms to avoid interferons by partially blocking their synthesis.

How do helminths produce disease symptoms in a host?

-some organisms use host tissues for their own growth or produce large parasitic masses; resulting cellular damage evokes the symptoms -waste products of the metabolism of these parasites can also contribute to symptoms

How are exotoxins named?

-type of host cells attacked (neurotoxin, cardiotoxin, etc.) -diseases with which they are associated (diphtheria toxin, etc.) -specific bacterium that produces them (botulinum toxin)

How does a microorganism damage the host cell?

-using the host's nutrients -causing direct damage in the immediate vicinity of the invasion -producing toxins, transported by blood and lymph, that damage sites far removed from the original site of invasion -inducing hypersensitivity reactions

Which of these effects is most likely to occur if a pathogen enters the body by a portal of entry other than the preferred one?

A milder disease will result.

Saxitoxin

A neurotoxin produced by some genera of dinoflagellates.

Superantigens

Antigens that provoke a very intense immune response. Bacterial proteins that interact with various cells of the immune system. Nonspecifically stimulate the proliferation of immune cells (T cells)

Shock

Any life-threatening decrease in blood pressure.

Adhesins or ligands

Attachment between a pathogen and its host is accomplished by means of surface molecules on the pathogen that bind specifically to complimentary surface receptors on the cells of certain host tissues. May be located on microbe's glycocalyx or on other microbial surface structures, such as pili, fimbriae, and flagella.

Which domain of the A-B toxin binds to cell surface receptors on the host cell?

B domain

The scum that builds up on shower doors, the formation of dental plaque on teeth, and the algae growth on the walls of swimming pools are all examples of __________.

Biofilms

Kinases

Bacterial enzymes that break down fibrin and digest clots formed by the body to isolate the infection.

Coagulases

Bacterial enzymes that coagulate (clot) fibrinogen in the blood. Fibrinogen (plasma protein produced by the liver) is converted into fibrin (threads forming a blood clot)

Aflatoxin

Can cause recall of peanut butter if found in excessive amounts. Has carcinogenic properties and is produced by the mold Aspergillus flavus. When ingested, might be altered in the human body to a mutagenic compound.

What happens when antibiotics are used to treat diseases caused by gram-negative bacteria?

Can lyse the cells, releasing endotoxin and may lead to immediate worsening of the symptoms, but the condition usually improves as the endotoxin breaks down.

Toxigenicity

Capacity of microorganisms to produce toxins

How can capsules enable bacteria to evade the immune system?

Capsules block the complement biding sites on the surface of the pathogen.

Membrane-disrupting toxins

Cause lysis of host cells by disrupting their plasma membranes. Some form protein channels in the plasma membrane, other disrupt the phospholipid portion of the membrane.

Endotoxic shock

Caused by gram-negative bacteria and is produced by endotoxins and their ability to trigger cytokine release by macrophages. Phagocytosis of gram-negative bacteria causes phagocytes to release tumor necrosis factor (TNF or cachectin), which binds to many tissues in the body and alters their metabolism.

intoxications

Caused by the presence of a toxin, not by microbial growth

Contact inhibition

Cell's do not stop growing when they come in close contact with other cells.

Which disease would be potentially propagated in an environment without functional plumbing and in which drinking water is contaminated with sewage?

Cholera

The pathogenicity of which of the following is NOT the result of lysogeny? A. Clostridium botulinum B. Clostridium tetani C. Vibrio cholerae D. Streptococcus pyogenes E. Corynebacterium diphtheriae

Clostridium tetani

Which one of these pairs is not correctly matched? A. collagenase; breaks down connective tissue B. coagulase; lyses fibrin clots C. leukocidin; lyses WBC membranes D. siderophore; traps iron E. IgA protease; digest antibodies

Coagulase; lyses fibrin clots

Which of these organisms does NOT produce an enterotoxin? A. Shigella spp. B. Clostridium botulinum C. Vibrio cholerae D. Staphylococcus aureus

Colostridium botulinum

Given the following LD50 values for Bacillus anthracis, through which portal of entry is it easiest to get anthrax? A. Cutaneous: 50 endospores B. Inhalation: 20,000 endospores C. Ingestion: 1 million endospores D. All of the listed choices are equally easy portals of entry.

Cutaneous: 50 endospores

An exotoxin that has the ability to kill or damage host cells is referred to as a(n)

Cytotoxin

Virulence

Degree of pathogenicity

M protein

Heat and acid resistant protein found on both the cell surface and fimbriae and contributes to virulence. Mediates attachment of bacterium to epithelial cells of the host and helps bacterium resist phagocytosis by WBC. (Steptococcus pyogenes)

How do exotoxins work on the body?

Destroy particular parts of the host's cells or by inhibiting certain metabolic functions. Highly specific in their effects on body tissues and are among the most lethal substances known.

How are endotoxins released?

During bacterial multiplication and when gram-negative bacteria die and their cell walls undergo lysis.

Streptolysins

Hemolysins produced by streptococci. -Streptolysin O (SLO) is inactivated by atmospheric oxygen. -Streptolysin S (SLS) is stable in an oxygen environment. Both can cause lysis of RBC, WBC, and other body cells.

Which of the following toxins is NOT produced by a bacterium as a result of lysogenic conversion?

Endotoxin

You conduct a Limulus amebocyte lysate (LAL) assay on a sample of fluid that should be sterile. The result is positive. What does this indicate?

Endotoxin is present.

Which of these events leads to all of the others in a pyrogenic (fever) response? A. Endotoxin is released from the cell wall of gram-negative bacteria. B. The hypothalamus releases prostaglandins. C. IL-1 is released by macrophages. D. The body's thermostat is set to a higher level, and fever occurs. E. IL-1 travels via the blood to the hypothalamus

Endotoxin is released from the cell wall of gram-negative bacteria.

Disseminated intravascular coagulation (DIC)

Endotoxin release causes the activation of blood-clotting proteins, causing the formation of small blood clots. These clots obstruct capillaries, resulting in decreased blood supply to tissues, which may cause them to die.

What happens when super antigens cause T cells to release large amounts of cytokines?

Enter the bloodstream and give rise to several symptoms, such as shock, fever, nausea, vomiting, diarrhea, and death.

Most pathogens that gain access through the skin

Enter through hair follicles and sweat ducts.

Hyaluronidase

Enzyme secreted by certain bacteria that hydrolyzes hyaluronic acid, a type of polysaccharide that hold together certain cells of the body, particularly cells in connective tissue. Digesting action is thought to be involved in the tissue blackening of infected wounds and to help the microorganism spread from its initial site of infection.

IgA proteases

Enzyme that can destroy IgA antibodies- antibodies produced as a defense against adherence of pathogens to mucosal surfaces.

Some organisms are capable of orchestrating alterations that are collectively termed antigenic variation. This allows an organism to __________.

Evade the host's immune system

Which of the following statements about lysogenic conversion is true?

Exotoxin production by bacteria is frequently the result of a lysogenic infection.

Exoenzymes

Extracellular enzyme that are thought to increase virulence of bacteria. They digest materials between cells and form or digest blood clots, among other functions.

Collagenase

Facilitates the spread of gas gangrene. Breaks down the protein collagen, which forms the connective tissue of muscles and other body organs and tissues.

Which of the following would be the first sign of an infection that resulted in the release of endotoxin?

Fever

Which type of bacterial enzyme helps spread Streptococcus pyogenes by digesting blood clots?

Fibrinolysin

What cell structures does Neisseria gonorrhoeae use to attach and enter host epithelial cells?

Fimbriae

A-B toxins

First toxins to be studied; named because they consist of two parts designated A and B, both of which are polypeptides. Most exotoxins are A-B toxins.

How do microorganisms gan access to the gastrointestinal tract?

Food, water, and contaminated fingers

Mycotoxins

Fungal toxins produced in mushrooms, such as phalloidin and amanitin

What are capsules?

Glycocalyx material that forms around cell walls, which increases virulence.

Cadherin

Glycoprotein used by Listeria and Shigella, which bridges the membrane junctions that form part of the transport network between host cells, to move from cell to cell.

What are the most common types of adhesins?

Glycoproteins and lipoproteins

Antibiotics can lead to septic shock if used to treat

Gram-negative bacterial infections.

Inclusion bodies

Granules are sometimes viral parts- nucleic acids or proteins in the process of being assembled into virions. Vary in shape, size, and staining properties. Characterized but heir ability to stain with an acidic stain (acidophilic) or basic stain (basophilic). Important in helping to identify the causative agent.

Which of the following is NOT considered entry via the parenteral route?

Hair follicle

Which of these statements is NOT true for bacterial capsules? A. Immune system antibodies are not produced against a capsule. B. Capsules related to virulence are produced by the causative agents of anthrax and bubonic plague. C. Pathogenic and nonpathogenic bacteria can produce capsules. D. The importance of the capsule to virulence for Streptococcus pneumoniae can be determined because there are strains both with and without the capsule. E. For Streptococcus pneumoniae, the encapsulated strain is more virulent.

Immune system antibodies are not produced against a capsule.

The mechanism by which gram-negative bacteria can cross the blood-brain barrier?

Inducing TNF

Which is a method of avoiding phagocytosis?

Inducing endocytosis

Which one of these is NOT an example of pathogen entry via the parenteral route?

Infection of a hair follicle

Which of the following diseases is NOT usually contracted by the respiratory route?

Infectious hepatitis

Pseudomonas aeruginosa produces a two-part exotoxin. The most likely pathologic effect of this toxin is

Inhibition of protein synthesis.

How does the protozoan Trypanosoma evade detection by the immune system?

It can change the surface antigens frequently, preventing the immune system from tracking it.

Why is a release of endotoxin into the bloodstream potentially deadly?

It can lower blood pressure and cause the patient to go into shock.

Which of the following statements about M protein is false?

It is readily digested by phagocytes.

Which of the following is NOT a method of avoiding host antibodies?

Membrane-disrupting toxins

Hemolysins

Membrane-disrupting toxins that destroy erythrocytes, produced mainly by streptococci and staphylococci

Leukocidins

Membrane-disrupting toxins that kill phagocytic leukocytes; act by forming protein channels. Active against macrophages, which are phagocytes present in most tissues. Produced mainly by streptococci and staphylococci.

How do biofilms form?

Microbes adhere to a particular surface that is typically mouse and contains organic matter. First microbes to attach are usually bacteria. Once they adhere to a surface, they multiply and secrete a glycocalyx that further attaches the bacteria to each other and to the surface.

Biofilms

Microbes have the ability to come together in masses, cling to surfaces, and take in and share available nutrients in communities (dental plaque, algae, scum, etc.)

Portals of exit

Microbes tend to leave the body via specific routes in secretions, excretions, discharges, or tissue that has been shed. Generally relate to the infected part of the body, with microbes tending to use the same portal for entry and exit. Portals of exit let pathogens spread through a population by moving from one susceptible host to another.

Parenteral route

Microorganisms gain access to the body when they are deposited directly into the tissues beneath the skin or into mucous membranes when these barriers are penetrated or injured (cuts, wounds, surgery, bites, injections, punctures, mucous membrane splitting due to drying or swelling)

What are leukocidins?

Molecules that are capable of destroying phagocytes

Which of the following statements about adherence is true?

Most bacterial adhesins are glycoproteins or lipoproteins.

Adherence or adhesion

Most pathogens have a means of attaching themselves to host tissues at their portal of entry and is a necessary step of pathogenicity

The most frequently used portal of entry for pathogens are the

Mucous membranes of the respiratory tract.

Waxy lipid

Mycolic acid; makes up the cell wall and increases virulence be resisting digestion by phagocytes. Found on Mycobacterium tuberculosis, which can multiple inside of phagocytes.

Which of the following organisms exhibits antigenic variation?

N. gonorrheae

Meningitis and gonorrhea are caused by

Neisseria species.

A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)

Neurotoxin

Exotoxins

Produced inside some bacteria as part of their growth and metabolism and are secreted by the bacterium into the surrounding medium or released following lysis. Proteins; many are enzymes that catalyze only certain biochemical reactions.

Siderophores

Proteins secreted by some pathogens in order to obtain iron. Released into the medium, where they take iron away from iron-transport proteins by binding to the iron even more tightly. Once the iron-siderophore complex is formed, it is taken up by siderophore receptors on the bacterial surface. Then the iron is brought into the bacterium.

Toxemia

Refers to the presence of toxins in the blood

How do capsules protect the cell from the host?

Resist's host's defenses by impairing phagocytosis. Chemical nature of the capsule prevents phagocytic cell from adhering to the bacterium.

What are the most common portals of exit?

Respiratory and gastrointestinal tracts

What is the most frequent and easiest portal of entry for pathogens?

Respiratory tract

Noncytocidal effects

Result in cell damage, but not cell death.

Which would be the most UNLIKELY location to find adhesin molecules on a newly discovered bacterium? A. Ribosomes B. Glycocalyx C. Fimbriae D. Cell wall E. Capsule

Ribosomes

Which of the following organisms does NOT produce an exotoxin?

Salmonella typhi

How are exotoxins secreted?

Secreted to the outside of the bacterial cell that produces them.

Limulus amebocyte lysate (LAL) assay

Sensitive test to identify the presence of endotoxins in drugs, medical devices, and body fluids. Atlantic coast horseshoe crabs have hemolymph (blood) contains amebocytes (WBC) containing a large amount of protein (lysate) that causes clotting. In the presence of endotoxin, amebocytes in the hemolymph lyse and liberate their clotting protein. Resulting gel-clot (precipitate) is a positive test for the presence of endotoxin.

In mice, the LD50 for staphylococcal enterotoxin is 1350 ng/kg, and the LD50 for Shiga toxin is 250 ng/kg. Which of the following statements is true?

Shiga toxin is more lethal than staphylococcal enterotoxin.

Septic shock

Shock caused by bacteria.

Which of these substances does NOT protect a bacterium from phagocytosis? A. leukocidins B. siderophores C. capsule D. M protein

Siderophores

Cytokines

Small protein molecules produced by various body cells, especially T cells, that regulate immune responses and mediate cell-to-cell communication.

Lysogenic conversion

Some bacteriophages can incorporate their DNA into the bacterial chromosome, becoming a prophage, and thus remain latent and do not cause lysis of the bacterium. Such a state is called lysogeny, and cells containing a prophage are considered to be lysogenic. One outcome of lysogeny is that the host bacterial cell and its progeny may exhibit new properties encoded by the bacteriophage DNA. This change in characteristics of a microbe due to a prophage is lysogenic conversion. As a result, the bacterial cell is immune to infection by the same type of phage.

Adaptive immunity

Specific defensive response of the body to an infection or to antigens. In the presence of antigens, the body produces proteins (antibodies), which bind to the antigens to inactivate or destroy them.

The LD50 of Vibrio cholerae is 108 cells through the oral route. If the bacterial cells are ingested with bicarbonate, the LD50 drops to 104. Which of these explanations is the most likely?

Stomach acid decreases the virulence of Vibrio cholerae.

A person who attended a picnic early in the day develops a very high fever and is unresponsive by the evening. This person most likely has been exposed to a(n)

Superantigen

Septic shock due to gram-positive bacteria is caused by

Superantigens

How are superantigens different from other types of exotoxins?

Superantigens cause an overstimulation of the host immune system.

Measles viruses are capable of inactivating host defenses by

Suppressing the immune system.

Invasins

Surface proteins that rearrange nearby actin filaments of the cytoskeleton when a cell makes contact with the host cell plasma membrane.

Which of these conditions would NOT affect the ability of Streptococcus mutans to attach to teeth?

The absence of Actinomyces, a bacterium that can be part of dental plaque

How does a capsule help certain bacteria evade detection by the immune system?

The capsule is composed of polysaccharides that are similar to those found in the host; thus, the immune system does not recognize it as foreign.

How are immune cells able to detect foreign pathogens?

They are able to detect structures on the surfaces of foreign cells that are not found in the host.

What do hyaluronidase and kinase have in common?

They are both enzymes involved in evading host defense.

Which statement is NOT true of endotoxins? A. They are eliminated from the body as a result of antitoxin production. B. They are more heat-resistant than exotoxins are. C. They can lyse amoebocytes found in crab hemolymph. D. They can induce chills, fever, aches, clotting, shock, and miscarriage. E. Endotoxins are produced by Neisseria meningitidis and E. coli.

They are eliminated from the body as a result of antitoxin production.

Which of the following statements about exotoxins is generally false?

They are not destroyed by heat.

Which of the following statements is NOT true of A-B exotoxins? A. Many exotoxins are A-B toxins. B. They consist of two polypeptide components. C. They are produced only by gram-negative bacteria. D. The A portion of the toxin is the active component. E. The B portion of the toxin binds to surface receptors on host cells.

They are produced only by gram-negative bacteria.

Which of the following is an accurate statement about A-B toxins?

They are proteins.

Which statement is true of endotoxins?

They are released upon cell lysis.

How do superantigens enable pathogens to hide from the immune system if they actually stimulate the immune system?

They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen.

Cytocidal effects

Those effects that result in cell death.

In which of the following cases would the Limulus amebocyte lysate (LAL) assay be used?

To ensure that a sterilized medical device is free of endotoxin

T/F: Endotoxins are made of lipopolysaccharides, while exotoxins are made of protein.

True

Which of the following microorganisms actually grows inside the macrophage?

Tuberculosis bacterium

Phallodin and amanitin

Types of mycotoxins produced by Amanita phalloides or the death cap. Neurotoxins that are so potent that ingestion of the mushroom may result in death.

T cells

Types of white blood cells (lymphocytes) that act against foreign organisms and tissues (transplants) and regulate the activation and proliferation of other cells of the immune system. In response to super antigens, they are stimulated to release enormous amounts of chemicals (cytokines)

What are most receptors made of?

Typically sugars, such as mannose

ID50

Used to express the virulence of a microbe; infectious dose for 50% of the sample population. 50 is not an absolute value, but is used for comparing relative virulence under experimental conditions.

Syncytium

Very large multinucleate cell; giant cells are produced from infections by viruses that cause measles, mumps, and the common cold.

Which of the following toxins does NOT match the description? A. Vibrio enterotoxin: a superantigen that destroys epithelial cells B. tetanus toxin: an A-B neurotoxin that causes uncontrollable muscle contractions C. streptococcal erythrogenic toxin: a superantigen that damages capillaries and results in a characteristic rash D. hemolysins: membrane-disrupting toxins that destroy erythrocytes

Vibrio enterotoxin: a superantigen that destroys epithelial cells

Cytopathic effects are changes in host cells due to

Viral infections.

Cytopathic effects (CPE)

Visible effects of viral infection.

Toxoids

When exotoxins are inactivated by heat, formaldehyde, iodine, or other chemicals, they no longer cause disease but can still stimulate the body to produce antitoxins. When injected into the body as a vaccine, they stimulate antitoxin produce so that immunity is produced.

When would endotoxins be released from a bacterial cell?

When the cell dies

LD50

used to express the potency of a toxin; lethal dose for 50% of a sample population.