Host-Microbe Interactions Overview

Symbiotic relationships

Interactions categorized as mutualistic, commensal, or parasitic.

Normal microbiota

Microorganisms residing in/on healthy individuals.

Hygiene hypothesis

Theory suggesting lack of microbe exposure leads to allergies.

Infection establishment

Process of pathogen colonization and multiplication.

Sign vs. symptom

Objective vs. subjective indicators of infection.

Primary pathogen

Microbe causing initial infection.

Opportunistic pathogen

Microbe causing infection under specific conditions.

Virulence

Degree of pathogenicity of a microorganism.

Virulence factor

Attribute promoting pathogenicity in a microorganism.

Communicable/contagious

Diseases transferable between hosts.

Infectious dose

Amount of microbes needed to cause disease.

Incubation period

Time between pathogen introduction and illness onset.

Illness

Signs and symptoms of a disease.

Convalescence

Recovery period after illness.

Carrier

Individual spreading pathogens without showing symptoms.

Localized infection

Infection confined to a specific area of the body.

Systemic infection

Infection spreading throughout the body.

Bacteremia

Presence of bacteria in the bloodstream.

Toxemia

Presence of toxins in the bloodstream.

Viremia

Presence of viruses in the bloodstream.

Koch's postulates

Steps to identify the cause of an infectious disease.

Molecular Koch's postulates

Modern approach to identify disease-causing agents.

Adherence

Bacteria sticking to host tissues.

Colonization

Establishment and multiplication of microbes on body surfaces.

Invasion

Microbes entering host tissues.

Immune evasion

Microbes avoiding host immune responses.

Direct effect by toxins

Toxins causing harm to host cells.

Indirect damage

Harm caused by microbial activities other than toxins.

Latent infections

Pathogen remains in host tissues without symptoms for years

Septicemia

Life-threatening illness from infectious agents in the bloodstream

Koch's Postulates

Criteria to establish the cause of infectious diseases

Pathogenicity

Methods used by microbes to evade host defenses and cause damage

Exotoxins

Proteins with specific damaging effects, often secreted by pathogens

Neurotoxins

Toxins damaging the nervous system, causing paralysis

Enterotoxins

Toxins causing intestinal symptoms like diarrhea and vomiting

Cytotoxins

Toxins damaging various cell types by interfering with mechanisms

A-B Toxins

Toxins usually containing a toxic enzyme

Membrane-Damaging Toxins

Toxins disrupting eukaryotic plasma membranes, causing lysis

Superantigens

Toxins causing overstimulation of the T cell immune response

Endotoxin

Lipopolysaccharide triggering immune response in Gram-negative bacteria

Immune complexes

Formed when antibodies bind to antigens, can cause destructive inflammation

Cross-reactive antibodies

Antibodies binding to body's own tissues, causing autoimmune response