Microbe-Human Interactions

Mutualism

Both organisms benefit

Commensalism

One organism benefits

Parasitism

One organism benefits and one organism is harmed

Symbiotic relationships

Two organisms living in close interaction with one another

Symbiotic relationship examples

Mutualism, commensalism, parasitism

Nonsymbiotic relationships

Relationships not required for survival of either organism

Nonsymbiotic relationship examples

Synergism, antagonism

Antagonism

Relationship between normal microbiota and pathogens where normal microbiota harm pathogens

Synergism

Relationship between multiple organisms that is beneficial but not required

Normal microbiota

Permanently colonize the host and do not cause disease under normal conditions

Infection

Contamination or invasion of body tissue by pathogenic organisms

Disease

An abnormal state in which the body is not functioning normally

Infectious disease

A disease that is caused by a pathogen and that can be spread from one individual to another

Communicable

Disease that may be transmitted directly or indirectly from one individual to another

Non communicable

Disease that is not transmitted from one host to another

Contagious

Able to be passed easily from one person to another

True pathogen

Microorganisms capable of causing disease in healthy individuals (functioning host defenses) under the right circumstances

Opportunistic pathogen

Microbes (exogenous or endogenous) that cause disease only in hosts with weakened defenses

Pathogenicity

Ability of a pathogen to infect a person

Virulence

Ability of a pathogen to cause disease

Virulence factor

Any characteristic of a pathogen that assists it in causing disease

Adhesion virulence factors

Capsule, fimbriae, adhesion proteins

Evasion of host defenses virulence factors

Capsule, mycolic acid, antigenic variation, intracellular life

Direct damage to host virulence factors

Use/steal host nutrients, exoenzymes (secreted), exotoxins (secreted)

Exoenzymes

Coagulase, kinase, hyaluronidase

Exotoxins

Cytotoxins, neurotoxins, enterotoxins, membrane-disrupting exotoxins

Indirect damage to host virulence factors

Endotoxin, superantigens

Viral virulence factors

Adhesion, evasion of host defenses, antigenic variation & intracellular life, damage to host