NURS 236: Human-Microbe Interactions Quiz

Human-Microbe Interactions: Principles of Disease and Transmission

• This course, NURS 236, focuses on human-microbe interactions and disease transmission.
• Learning objectives include recalling predisposing factors for disease, explaining disease stages, exploring infection reservoirs, contrasting transmission methods, and providing examples.

Patterns of Disease

• Predisposing Factors: Any factor that increases a host's susceptibility to infection or alters disease progression.
  • Examples include gender (UTIs, pneumonia), genetics (sickle-cell anemia, malaria), climate (MO survival), environment, lifestyle, and occupation.
• Stages of Disease:
  • Incubation period: Initial infection to first symptoms, early, mild symptoms; might be absent in some diseases.
  • Prodromal period: Early, mild symptoms; relatively short; may not be present in all diseases (due to virulence).
  • Period of illness: Most severe signs and symptoms; major immune response occurs.
  • Period of decline: Symptoms decrease, susceptibility to secondary infections increases.
  • Period of convalescence: Return to normal/homeostasis. -Stages can link to stages of microbial growth. Different microbes may have varying periods for each phase.

Spread of Infection: Reservoirs

• Reservoirs: Source of disease-causing microbes.
• 3 major groups:
  • Humans:
    • Symptomatic individuals.
    • Asymptomatic individuals (e.g., carriers like hospital staff with MRSA).
    • During incubation/convalescence stages of disease (e.g., STIs, streptococcal infections).
  • Animals:
    • Zoonoses: Diseases transferred from animals to humans.
    • Spread through many routes (direct contact with animal/feces, contaminated water/food/products/hides).
    • Can be transmitted by arthropods (insect vectors).
  • Nonliving:
    • Environmental sources of infection.
    • Soil: Fungi, nematodes, Clostridium tetani, C. botulinum.
    • Water: Protozoa, some helminths.
    • Food: Food poisoning (e.g., salmonellosis).

Spread of Infection: Transmission

• 3 Modes: Contact, vehicles, vectors.
• Contact:
  • Direct Contact: Physical contact (touching, kissing) between sources and hosts. Common cold, influenza, Hepatitis A, measles, STIs. Prevention via protective equipment.
  • Indirect Contact: Physical contact through nonliving objects (e.g., HIV or hepatitis B in contaminated syringes, organisms living in a hospital environment). Prevention by maintaining a clean environment.
  • Droplet: Contact with aerosolized liquid containing microbes (<1 m). Influenza, whooping cough. Prevention via good hygiene.
• Vehicle Transmission: Diseases transmitted by a medium.
  • Water: Fecal contamination (cholera, leptospirosis)
  • Food: Poor cooking/storage (food poisoning, tapeworms).
  • Air: Similar to droplet (larger distances); airborne microbes/dust (tuberculosis, fungal infections).
• Vectors: Microbes transmitted between hosts by another organism (typically an insect).
  • Mechanical: Passive transport by insect from vector's body to food (typhoid fever).
  • Biological: More active and complex; some phase of microbial life cycle occurs in a vector (malaria by Plasmodium species).

Nosocomial Infections

• Infections acquired during a hospital or other healthcare-associated visit.
• Increasing frequency.
• Interaction between 3 factors (microorganisms in the hospital environment, compromised host, chain of transmission).
  • Microorganisms: Common in hospital environment. Resistance to cleaning agents and antibiotics.
  • Compromised Host: Many body structures prevent illness; these structures can be broken (open wounds, skin), or the immune system can be weakened.
  • Chain of Transmission: Mostly through direct and indirect contact between hospital staff and patients, or between patients, or shared equipment.

Emerging Infectious Diseases

• Diseases that either appear for the first time or change in a manner that increases incidence.
• Factors Influencing Emergence:
  • New Diseases: (e.g., HIV). Zoonotic diseases that newly infect humans (e.g., West Nile virus, smallpox).
  • Genetic: Acquisition of new traits (e.g., antibiotic resistance, toxin production).
  • Environmental: Movement of microbes, reservoirs, or vectors to new areas, climate change altering disease patterns.

Important terms

• Pathology: Scientific study of disease.
• Etiology: Cause of a particular disease, often a specific microorganism.
• Pathogenesis: Steps in the progression of a disease.
• Infection: Pathogenic microorganism enters a host and begins to grow.
• Disease: Change in a host's state of health associated with infection.

Many MOs on the human body

• Microbiomes impacted by many factors.
• Differences between Normal and Transient Microbiota:
  • Normal: Normally found on the body.
  • Transient: Live on/in the body for a period of time and then leave.
  • Differences exist among individuals.

Example Human-Microbe Relationships

• Relationships: Commensalism (one benefits, other unaffected); mutualism (both benefit); parasitism (one benefits at expense of other) are affected by conditions and potentially by opportunistic pathogens like Candida albicans and Clostridium difficile.

This quiz covers the principles of disease and transmission in the context of human-microbe interactions. Students will explore predisposing factors, stages of disease, and methods of disease transmission. Prepare to demonstrate your understanding of how various factors influence infection susceptibility.