Microbial Mechanisms of Pathogenicity - ch 16

Flashcards covering key vocabulary related to microbial mechanisms of pathogenicity.

Pathogenicity

The ability of a microbe to cause disease.

Portals of Entry

Sites through which pathogens enter the body (e.g., mucous membranes, skin, parenteral route).

Adherence

The process by which microbes attach to host cells, often using adhesions.

Invasins

penetration or evasion of host defesnes - Substances or structures that allow microbes to penetrate or evade host defenses.

Siderophores

damage to host cell - Bacterial iron-binding proteins that steal iron from the host.

Toxins

Poisonous substances produced by microorganisms that damage host cells.

Exotoxins

Toxins, often proteins, secreted by living bacteria.

Endotoxins

Toxins composed of Lipid A, which is part of the lipopolysaccharide (LPS) of the outer membrane of gram-negative bacteria; released upon cell lysis.

can stimulate fever

damage associated with inflammation

LPS activates both innate and adaptive responses

macrophages—>release cytokines—>fever and inflammation

b cells—> non-specific activation

invasion of pathogens

penetration of skin and mucous membranes

Lysogenic Conversion

A change in the characteristics of a microbe due to incorporation of a prophage.

which is more common route of infection, skin or mucous membrane?

mucous membrane

Capsules

A structure that prevent encounters with phagocytes.

Protein A

A protein that binds to the Fc region of antibodies, preventing opsonization and phagocytosis.

Exoenzymes

Extracellular enzymes secreted by microbes to break down tissues and aid in spread.

Coagulase

An exoenzyme that clots fibrinogen in the blood.

Kinases

Enzymes that digest clots to allow spread of microbe (e.g., streptokinase).

Collagenase

An exoenzyme that breaks down collagen.

A-B Toxins

Exotoxins with two parts: A (active component) and B (binding component).

mechanism: AB toxin released from bacterium, B part binds to surface receptor on cell, AB toxin after binding will be transported across P.M. into host cell cytoplasm, A inhibits protein synthesis and kiss host cell whereas B goes on to be released from cell

Membrane-Damaging Toxins

Toxins that disrupt plasma membranes, leading to host cell lysis.

Superantigens

Toxins that trigger massive cytokine release by T cells.

LD50 (Lethal Dose 50%)

The dose of a toxin required to kill 50% of exposed subjects.

measurement to compare potency of different toxins

Neurotoxins

Toxins that damage the nervous system.

Enterotoxins

Toxins that cause intestinal symptoms.

Cytotoxins

Toxins that lyse cells or interfere with cell function.

Hemolysins

Substances that cause lysis of red blood cells.

Phospholipases

Enzymes that damage cell membranes by breaking down phospholipids.

Lipid A

The active component of endotoxin (LPS).

Septic Shock

A condition caused by large amounts of endotoxin triggering systemic inflammation and blood clotting.

DIC (Disseminated Intravascular Clotting)

A condition characterized by systemic blood clotting.

coagulation

adherence

adhesion allows microbes to bind to specific cell types

infection; growth of microbe

damage to host

evasion of host defenses

hiding within host cell

evasion of complement

evasion of phagocytosis

avoiding antibodies

exoenzymes

antigenic variation

microbes damage host cells by

using host nutrients

direct damage by invasion

producing toxins

inducing hypersensitivity reactions

membrane damaging toxins that disrupts plasma membrane causing host cell lysis

pore formation

phospholipase

portal of exit for microbes

allow for spread of infection

bodily secretions

blood

skin shedding