Microbiology: Infection, Infectious Diseases, and Epidemiology Summary

Symbiotic Relationships

• Symbiosis: Means "to live together"; involves interactions between microorganisms and hosts.

• Types:

  • Mutualism: Both organisms benefit.

  • Commensalism: One benefits, the other is unaffected.

  • Amensalism: One is harmed, other is unaffected.

  • Parasitism: One benefits at the expense of the other.

Human Microbiome

• Normal Microbiota: Organisms that colonize the body without causing disease.

  • Resident Microbiota: Permanent; mostly commensal.

  • Transient Microbiota: Temporary, cannot persist in the body due to competition and defenses.

• Acquisition: Begins at birth, develops through early months of life.

Pathogen Reservoirs

• Reservoirs: Sites where pathogens are maintained.

  • Animal Reservoirs: Diseases (zoonoses) spread from animals to humans.

  • Human Carriers: Asymptomatic individuals can transmit infections.

  • Nonliving Reservoirs: Contaminated water, food, and soil.

Infection and Disease

• Infection: Invasion by a pathogen that multiplies and establishes itself.

• Contamination: Presence of microbes.

• Stages of Infectious Disease:

  • Incubation

  • Prodromal

  • Illness

  • Decline

  • Convalescence

Modes of Transmission

• Contact Transmission:

  • Direct: Physical interaction between hosts.

  • Indirect: Via fomites.

  • Droplet: Transfers through respiratory droplets.

• Vehicle Transmission:

  • Airborne: Long-range spread via aerosols.

  • Waterborne & Foodborne: Contaminated sources.

• Vector Transmission:

  • Biological: Active host (e.g., mosquitoes).

  • Mechanical: Passive transport (e.g., flies).

Epidemiology of Diseases

• Incidence: New cases over time; Prevalence: Total cases.

• Public Health Agencies: Track diseases, enforce policies, and implement preventive measures.