Lec 14 - Microbial Mechanisms of Pathogenicity - Exam 3

What is pathogenicity?

The ability of a microorganism to cause disease.

What is a pathogen?

A disease-causing microorganism.

What is a true pathogen?

A microorganism that can cause disease in a healthy host.

What is an opportunistic pathogen?

A microorganism that causes disease when host defenses are weakened or conditions allow it.

What is virulence?

The degree or severity of pathogenicity.

What is infectious dose?

The number of microorganisms needed to establish an infection.

What is ID50?

The dose of a pathogen that infects 50% of a test population.

What is LD50?

The dose of a toxin that kills 50% of a test population.

What does a low ID50 indicate?

Greater infectious potential and generally greater virulence.

What is a portal of entry?

A route through which a pathogen enters the body.

What are five major portals of entry?

Skin, gastrointestinal tract, respiratory tract, urogenital tract, and transplacental route.

What does exogenous mean?

Coming from outside the body.

What does endogenous mean?

Coming from within the body, such as normal microbiota.

What is adhesion?

The process by which microorganisms attach to host cells.

What are adhesins?

Microbial molecules that bind to host-cell receptors.

What are receptors?

Specific structures on host cells that pathogens attach to.

What structures help microbes attach to host cells?

Fimbriae, pili, flagella, capsules, glycocalyx, hooks, and surface proteins.

What structure does E. coli use for adhesion?

Fimbriae.

What structure does Neisseria gonorrhoeae use for adhesion?

Type IV pili.

What structure does Streptococcus pyogenes use for adhesion?

M protein.

What structure does Vibrio cholerae use for adhesion?

Glycocalyx.

What structure does HIV use for attachment?

Surface spikes.

What structure does influenza use for attachment?

Surface spikes.

What is a biofilm?

A community of microorganisms attached to a surface and surrounded by extracellular material.

What are examples of biofilms?

Dental plaque, shower buildup, contact lenses, catheters, and artificial hip replacements.

Why are biofilms difficult to eliminate?

Their extracellular material protects microorganisms and can increase resistance to certain antibiotics and disinfectants.

What are exoenzymes?

Enzymes released outside microbial cells that help break down substances and invade tissues.

What does amylase break down?

Starch.

What does gelatinase break down?

Gelatin.

What does coagulase do?

Causes blood clotting.

What do kinases do?

Break down fibrin clots.

What does collagenase break down?

Collagen.

What is a toxin?

A poisonous substance produced by a microorganism.

What is toxinosis?

Harmful effects caused by toxins.

What is toxemia?

Toxin circulating through the bloodstream.

What is intoxication?

Disease caused by consuming a toxin.

What is endotoxin?

A toxic component of the outer membrane of Gram-negative bacteria.

What is the toxic component of endotoxin?

Lipid A.

When is endotoxin commonly released?

When Gram-negative bacterial cells are damaged or destroyed.

Can antitoxins neutralize endotoxin?

No.

What is an exotoxin?

A protein toxin secreted by living bacterial cells.

Can Gram-negative bacteria produce exotoxins?

Yes. Both Gram-positive and Gram-negative bacteria can produce exotoxins.

Can antitoxins neutralize exotoxins?

Generally, yes.

What is an A-B toxin?

An exotoxin in which B binds to the target cell and A produces the harmful effect.

What is an example of an A-B toxin?

Diphtheria toxin.

What is a superantigen?

A toxin that causes excessive, nonspecific immune activation.

What is a membrane-disrupting toxin?

A toxin that damages cell membranes or creates channels.

What are hemolysins?

Toxins that damage red blood cell membranes.

What is the main difference between endotoxin and exotoxin?

Endotoxin is LPS containing Lipid A; exotoxin is a secreted protein.

How do bacterial capsules help pathogens?

They help bacteria avoid phagocytosis.

How does Salmonella invade intestinal cells?

It attaches using fimbriae, injects proteins, causes actin rearrangement and membrane ruffling, and is engulfed into a vacuole.

What is a portal of exit?

A route through which a pathogen leaves its host.

What are common portals of exit?

Respiratory secretions, skin, feces, urine, reproductive secretions, and blood.

What is the incubation stage of infection?

The pathogen enters and multiplies, but obvious symptoms have not appeared.

What is the prodromal stage?

Early, vague symptoms begin.

What is the invasion stage?

The disease becomes more severe and characteristic symptoms appear.

What is the convalescent stage?

The patient begins recovering.

What is a localized infection?

An infection limited to one area.

What is a systemic infection?

An infection that spreads throughout the body.

What is a focal infection?

A localized infection that spreads to another location.

What is a mixed infection?

An infection caused by multiple microorganisms.

What is a primary infection?

The original infection.

What is a secondary infection?

An additional infection that develops following a primary infection.

What is an acute infection?

An infection with rapid onset and usually short duration.

What is a chronic infection?

An infection that lasts for a long time.