Mechanisms of Pathogenicity

A compilation of key terms and definitions regarding the mechanisms of pathogenicity and related concepts.

Pathogenicity

The ability of a microorganism to cause disease.

Virulence

Degree of pathogenicity.

Exotoxins

Toxins secreted by bacteria that can destroy parts of host cells or inhibit metabolic functions.

Endotoxins

Part of the outer membrane of gram-negative bacteria that can cause septic shock when released.

ID50

The number of pathogenic cells required to cause infection in 50% of a sample population.

LD50

The number of pathogenic cells or toxins required to kill 50% of a sample population.

Incubation period

The time between infection and the appearance of signs and symptoms.

Prodromal period

The stage of disease when early symptoms appear but are not yet specific.

Syndrome

A specific group of signs and symptoms characteristic of a particular disease.

Opportunistic pathogen

Pathogens that cause disease only when the host's defenses are compromised.

Adhesins

Molecules that allow pathogens to attach to host cells.

Virulence factors

Specific characteristics of pathogens that contribute to their ability to cause disease, such as toxins and adhesion factors.

Zoonotic diseases

Diseases transmitted from animals to humans.

Nosocomial infections

Infections acquired in a hospital setting.

Iatrogenic diseases

Diseases caused by medical procedures.

Primary infection

The initial infection in a host caused by a pathogen.

Secondary infection

An infection caused by a second pathogen following the primary infection.

Koch's postulates

A series of criteria to establish the cause of an infectious disease.

Antigenic variation

The ability of pathogens to change their surface antigens to evade host immune responses.

Biofilms

Communities of bacteria that adhere to surfaces and are surrounded by a self-produced matrix.

Virulence factors: Exoenzymes

Enzymes that help pathogens colonize tissues and evade host immune responses.

Pathogen

An organism that causes disease.