Infection and Immunity Quiz

Study Notes

Host: An organism that provides nutrients to another organism
Parasite: An organism living at the expense or harming its host, generally smaller than the host and metabolically dependent upon it
Disease: An upset in the host's homeostasis, causing observable changes
Symptom: Subjective evidence of damage (e.g., headache, anorexia)
Sign: Objective evidence of damage (e.g., fever, rash, vomiting)
Infectious disease: Detrimental changes in the host's health due to parasite damage
Pathogen: A microorganism capable of causing disease

Virulence: A measure of pathogenicity, the ability to cause disease
Virulent: Microorganisms readily causing disease; only small numbers are needed to initiate and sustain infection
Opportunistic: Microorganisms that often colonize the host but do not cause disease, unless introduced to an unusual site, and normal healthy microbiota, can cause disease if introduced into the wrong site
Avirulent: Microorganisms that do not cause disease
Attenuated: Microorganisms with reduced ability to cause disease

If a microorganism is the causative agent of a disease, it should be:
- Present in every case of the disease, but absent in healthy hosts
- Isolated and grown in pure culture
- Able to cause disease when a pure culture is inoculated into a healthy host
- Re-isolated from the inoculated host

Adhesins: Promote attachment to host cells and tissues
- Examples: Pili in Escherichia coli and Neisseria gonorrhoeae attach to urethral cells; Salmonella and Escherichia coli attach to intestinal cells

Antigen: Any substance capable of inducing an immune response in an organism
Antibody: A protein (immunoglobulin molecule) produced by the organism in response to antigen stimulation.