Infection and Immunity Quiz

Infection and Immunity

• 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

• 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

Koch's Postulates

• 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

Steps in Pathogenesis

• To cause disease, a pathogen must:
  • Contact the host (be transmissible)
  • Colonize the host (adhere to and multiply on host surfaces)
  • Infect the host (proliferate in host cells or tissues)
  • Evade the host defense system (avoiding damage)
  • Damage host tissues.

Virulence Factors

• 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 and Antibody

• 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.

Test your knowledge on infection and immunity concepts. This quiz covers definitions and distinctions between hosts, parasites, diseases, symptoms, and signs, along with virulence and pathogens. Perfect for students studying biology or health sciences.