MICR 300 Medical M&I

infection

A microbe is actively dividing inside the tissue of the host cell

disease

When infection causes damage, leading to signs and symptoms

pathogenicity

the ability of a pathogen to enter host cell tissues and cause disease

virulence

the degree of pathogenicity

true pathogen

A pathogen that can cause disease in anyone, regardless of their health and immune system

opportunistic pathogens

Avirulent; Unlikely to cause disease in healthy people, but can cause disease in immunocompromised people

signs

evidence of disease as detected by outside observers

symptoms

evidence of disease as detected by the patient/host

syndrome

collective term for signs and symptoms

incidental host

A host outside of a pathogen’s primary, natural transmission cycle. The pathogen did not evolve to rely on this host for its long-term survival in nature. Ex. The first human to contract COVID-19, which originated in bats

dead end host

An infected host that cannot generate a high enough pathogen load (or produce the necessary secretions/vectors) to transmit the disease to another susceptible host

human commensals

microbes that normally colonize humans without causing disease, but which can cause disease in immunocompromised people OR when entering a normally uncolonized part of the body

environmental pathogens

pathogens with reservoirs in the environment, which do not rely on living organisms to reproduce

human-adapted pathogens

pathogens that depend on humans as their primary or exclusive natural host and reservoir

transmission-virulence tradeoff hypothesis

The idea that natural selection favors a level of virulence that results in the greatest overall pathogen transmission; more virulence doesn’t always mean higher transmissionm

microbiota

Normal flora of microbes that live in and on and individual, including bacteria, archea, fungi, protozoa and viruses

microbiome

Aggregate collection of microbial genomes that are present in and on an individual

dysbiosis

Disruption or breakdown of the structure and functional activity of the microbiota; Leads to loss of beneficial microbes, proliferation of potentially harmful ones, and a loss of overall microbial diversity

eubiosis

Normal, healthy state of the microbiota, where trillions of bacteria, fungi and viruses live symbiotically with the host, aiding digestion, producing nutrients, supporting immune function, and protecting against opportunistic pathogens