Study Notes on Inflammation, Immunity, and Infections

Inflammation, Immunity, and Infections

Presented by: Julie B. Grant, PhD, RN, CNRN, SCRN

Key Terms

  • Infection: A state in which microorganisms, such as bacteria, viruses, fungi, or parasites invade and multiply within the host, leading to disruption of normal physiological functions and causing disease.
  • Asepsis: The absence of pathogens.
  • Medical Asepsis: Techniques employed to reduce the number of pathogens to prevent the spread of infections.
  • Surgical Asepsis: Methods to keep an area or object free from all microorganisms.
  • Antibodies: Proteins produced by the immune system in response to antigens.
  • Antigens: Substances that trigger an immune response, typically proteins on the surface of pathogens.
  • Colonization: When pathogens establish themselves within the host without necessarily causing disease.
  • Dormant: A state in which a pathogen is inactive, but can potentially reactivate.
  • Epidemic: A sudden increase in the number of cases of a disease within a specific population or area.
  • Pandemic: An epidemic that has spread over multiple countries or continents.
  • Morbidity: The condition of being diseased or the prevalence of disease within a population.
  • Mortality: The state of being subject to death; often referred to in terms of the death rate from a specific disease in a population.
  • Pathogen: A biological agent that causes disease or illness to its host.
  • Vector: An organism, often an insect, that transmits pathogens from one host to another.
  • Virulence: The degree of pathogenicity or severity of disease associated with a pathogen.

Infection Process

  • Understanding Infection:
    • Involves the invasion and multiplication of microorganisms causing disease and disrupting normal physiological functions.
  • Six Links in the Chain of Infection:
    • Essential stages of infection:
    1. Infectious Agent
    2. Reservoir
    3. Portal of Exit
    4. Mode of Transmission
    5. Portal of Entry
    6. Susceptible Host
    • Breaking any link can stop the infectious agent from spreading, making it a key strategy in infection control.

Link 1: Infectious Agent

  • Categories of Infectious Agents:
    • Bacteria:
    • Examples:
      • Staphylococcus aureus: Causes cellulitis, impetigo, and pneumonia.
      • Escherichia coli: Linked to urinary tract infections and gastroenteritis.
      • Streptococcus pyogenes: Associated with strep throat, cellulitis, scarlet fever, and necrotizing fasciitis.
    • Fungi:
    • Candida albicans: Causes thrush, vaginitis, nailbed infections, and fungal pneumonia particularly in immunocompromised patients.
    • Histoplasma capsulatum: Known for similar risks.
    • Helminths:
    • Examples:
      • Pinworms, tapeworms, roundworms (trichinosis), hookworms.
    • Prions:
    • Examples:
      • Creutzfeldt-Jakob Disease, Bovine spongiform encephalopathy (Mad Cow Disease).
    • Protozoa:
    • Examples:
      • Giardia lamblia, malaria, toxoplasmosis.
    • Viruses:
    • Examples:
      • SARS-CoV-2 (Covid-19), influenza (types A, B, C), swine flu, Epstein-Barr virus, hepatitis viruses, varicella-zoster virus, herpes viruses.
    • Health Care-Associated Infections (Nosocomial Infections):
    • Types include catheter-associated urinary tract infections (CAUTI), surgical site infections (SSI), ventilator-associated pneumonia (VAP), and central line-associated bloodstream infections (CLABSI).

Link 2: Reservoir

  • Types of Reservoirs:
    • Animate Reservoirs:
    • Includes animals, insects, and humans.
    • Inanimate Reservoirs:
    • Includes plants, water, soil, and medical devices.

Link 4: Mode of Transmission

  • Direct Transmission:
    • Methods include kissing, sexual contact, touching, coughing, and sneezing (droplet transmission).
  • Indirect Transmission:
    • Includes vehicle-borne transmission (contaminated objects), vector-borne transmission (via a vector), and airborne transmission (suspended in the air).

Link 5: Portal of Entry

  • Common Portals of Entry:
    • Gastrointestinal tract, genitourinary tract, mucous membranes, placenta, respiratory tract, skin.

Link 6: Susceptible Host

  • Factors Increasing Host Susceptibility:
    • Conditions such as burns, chronic diseases, immunocompromise, invasive procedures, malnutrition, stress, young age, and old age increase vulnerability to infections.

Body's Defense Mechanisms

  • Natural Immunity:
    • Comprises physical barriers (like skin), chemical barriers (such as mucus and acidic secretions), and microbiological barriers (normal flora).
  • Innate Immunity:
    • Involves mechanisms like enzymes in mucus, tears, saliva, etc., along with physiological responses like coughing and sneezing.
  • Adaptive Immunity:
    • A more specific immune response that develops after exposure to pathogens, including cellular and humoral responses.
  • Acquired Immunity:
    • Involves herd immunity where a significant portion of a population is immune, thus protecting even those who are not immune.

Inflammatory Response

  • Acts as the body’s final defense against infection.
  • Triggers cellular and molecular events designed to prevent the spread of infection and promote healing.

Infection Progression

  • Progression from localized infection to sepsis can occur if local bacterial infections are left untreated, especially in individuals with weakened immune systems.
  • Stages Involved:
    • Localized infection develops into a systemic bacterial infection, which may lead to severe outcomes without timely intervention.

Laboratory Assessment

  • Common Tests:
    • Gram Staining: Classifies bacteria into gram-positive or gram-negative and helps identify pathogens.
    • Antibody Testing: Detects specific immune responses to pathogens.
    • Culture Sensitivity Tests: Identify infectious organisms and determine effective antibiotics.
    • Complete Blood Count (CBC) and Erythrocyte Sedimentation Rate (ESR).

Medication Treatment of Infections

  • Treatment is guided by the type of pathogen involved.
  • Types of Anti-infective Agents:
    • Antibiotics:
    • Act against bacterial infections.
    • Types include:
      • Penicillin and Cephalosporins:
      • Effective against a range of gram-positive and gram-negative bacteria.
      • Pros: Affordable and effective.
      • Cons: Possible allergic reactions.
      • Generational distinctions exist for cephalosporins (1st to 4th generation).
      • Tetracyclines:
      • Prevents protein synthesis, effective against bacterial reproduction.
      • Cons: Risk of permanent staining in teeth for children and fetuses.
      • Aminoglycosides:
      • Effective against aerobic gram-negative bacteria.
      • Cons: More toxic; requires careful monitoring of blood levels.
      • Quinolones:
      • Effective against certain infections; monitor for side effects.
      • Sulfonamides:
      • Early class antibiotics effective for UTIs; noted for high allergy occurrence.
      • Macrolides:
      • Inhibit protein synthesis with variable effectiveness.

Antibiotic-Resistant Infections

  • Notable resistant infections include:
    • Methicillin-resistant Staphylococcus aureus (MRSA)
    • Vancomycin-resistant Enterococci (VRE)
    • Carbapenem-resistant Enterobacteriaceae (CRE)

Antibiotic-Associated Diarrhea (AAD)

  • Symptoms often resolve after stopping antibiotic therapy, but more serious cases like C. Diff may require further treatment.
  • Causes:
    • Disruption of gut microbiota balance allows harmful bacteria to proliferate, producing toxins.
  • Key Symptoms:
    • Up to 20+ stools per day, potentially life-threatening if untreated.

Other Anti-Infective Agents

  • Antituberculosis Agents:
    • Specifically target Mycobacterium tuberculosis.
    • Often administered in combination (two to four drugs) for extended periods (up to one year).
    • Examples:
    • Cycloserine (inhibits growth)
    • Rifampin (causes discoloration of body secretions).
  • Antiprotozoals:
    • Example: Metronidazole.
  • Antihelminthics:
    • Example: Pyrantel Pamoate for pinworms.

Nursing Responsibilities & Patient Education

  • Medication Monitoring:
    • Verify patient allergies and administer medications as ordered.
    • Monitor treatment side effects and effectiveness of medical interventions.
  • Assessment Responsibilities:
    • Early detection of signs/symptoms and ongoing patient assessment and communication.

Questions and Discussion

  • An opportunity for students and professionals to engage in dialogue regarding the material presented.