Microbial Mechanisms of Pathogenicity Flashcards

A complete set of vocabulary flashcards covering the microbial mechanisms of pathogenicity, including portals of entry, host defense avoidance, and the types of toxins.

Pathogenicity

The ability of a microorganism to cause disease.

Virulence factors

Specific characteristics that determine the extent of pathogenicity and aid a pathogen's ability to cause disease.

Portal of entry

The specific route or avenue by which a pathogen enters a host, such as the respiratory, gastrointestinal, or genitourinary tracts.

Parenteral route

A portal of entry where an organism is deposited directly into the tissues as a result of an injury like a knife wound or bullet wound.

STORCH

An acronym for pathogens that can cross the placenta and infect a fetus: Syphilis, Toxoplasmosis, Other (HIV and Chlamydia), Rubella, Cytomegalovirus, and Herpes simplex virus.

$$ID_{50}$$

The infectious dose for $50\%$ of the test population, indicating the number of organisms required to cause infection.

$$LD_{50}$$

The lethal dose for $50\%$ of the test population, primarily used when discussing the potency of toxins.

Adhesion

The process by which a microorganism attaches to the host after entry to avoid being expelled.

Skolex

A structure in tapeworms consisting of hooks and suckers used to embed in the host's intestinal wall.

Mycolic acid

A hydrophobic waxy layer found in the cell wall of pathogens like $Mycobacterium \, tuberculosis$ that resists digestion by the host defenses.

Coagulases

Bacterial enzymes that cause blood clots, allowing the pathogen to hide from the host immune system.

Kinase

A bacterial enzyme that breaks down host-formed clots to allow the pathogen to migrate through the host.

IgA protease

An enzyme that breaks down IgA antibodies to weaken the host immune response.

Antigenic drift

A process in RNA viruses like Influenza where random mutations create new antigens, necessitating yearly vaccinations.

Antigenic shift

A process seen only in Influenza A where two or more variations of a virus combine to create a unique subtype with new antigens.

Membrane ruffling

A process where pathogens alter host actin fibers to enter the host cell, as seen in $Salmonella$.

Leukocidins

Toxins produced by pathogens that are toxic to and kill white blood cells.

Siderophore

A molecule produced by pathogens to take iron from host cells to fuel their own metabolism.

Toxoid

Inactivated toxins used in vaccines to stimulate an immune response and the production of memory cells.

Antitoxins

Antibodies produced by the host immune response that are designed to bind with and inactivate specific toxins.

Exotoxins

Proteins primarily produced by Gram-positive cells that are heat-sensitive, actively secreted by living cells, and have a very low $LD_{50}$.

Endotoxins

Lipid components (specifically Lipid A) of the outer membrane of Gram-negative cells that are heat-resistant and released only upon cell lysis.

Superantigen

A type of exotoxin that stimulates an overwhelming immune response known as a cytokine storm, resulting in symptoms like fever, nausea, and shock.

Cytokine storm

An intense immune response involving the release of fluids and inflammation that can cause breathing difficulties and death.

Botulinum toxin

An AB neurotoxin that causes flaccid paralysis by preventing muscle contraction.

Tetanus toxin

An AB neurotoxin that causes permanent muscle contraction by preventing muscle cells from relaxing.

Inclusion bodies

Cytoplasmic sites of viral protein synthesis, such as Negri bodies which are used to diagnose rabies.

Mycotoxins

Secondary compounds produced by fungi that provide a chemical defense and can act as neurotoxins in humans.

Ergot toxin

A toxin produced by $Claviceps$ that is a precursor to LSD and has profound effects on the central nervous system.

Paralytic shellfish poisoning

A condition caused by toxins from algal blooms (dinoflagellates) that accumulate in filter-feeding shellfish.

Fecal-oral route

A transmission cycle where pathogens exit one host via feces and enter a new host through ingestion of contaminated material.