Infection & Inflammation Study Guide

Infection & Inflammation Study Guide

SECTION 1: The Chain of Infection

An infection requires all six links in the chain to be present. Breaking any link prevents infection.

• Link 1: Infectious Agent

  • Definition: Pathogens capable of causing disease.

  • Examples: Bacteria, fungi, viruses, parasites, prions (misfolded proteins).

• Link 2: Reservoir

  • Definition: Habitat where the agent lives, grows, and reproduces.

  • Example: Humans, soil, animals, water.

• Link 3: Portal of Exit

  • Definition: Route through which the infectious agent leaves the reservoir.

  • Examples: Respiratory secretions, blood, feces, urine.

• Link 4: Mode of Transmission

  • Definition: Mechanism by which the infectious agent is transmitted.

  • Types:

  • Direct Contact: Microorganisms move directly from infected person to another (no contaminated intermediary).

  • Indirect Contact: Microorganisms pass through a contaminated object or person between the two.

  • Droplet: Large respiratory particles (sneezing, coughing) that fall within approximately 3–6 feet.

  • Airborne: Tiny droplet nuclei that remain suspended in air requiring an N95 mask (e.g., TB, measles, chickenpox).

  • Vector: Transmitted via an arthropod/animal host (e.g., tick-borne Lyme disease).

• Link 5: Portal of Entry

  • Definition: Site where the agent enters the body and replicates.

  • Examples: Body orifices (ears, nose, mouth), skin breaks.

• Link 6: Susceptible Host

  • Definition: Individual at risk of infection who is exposed to the infectious agent.

  • Factors Influencing Susceptibility: Immune status, age, chronic diseases.

Risk Factors for Infection

Compromised Host Defenses

• Factors:

  • Immunocompromised status

  • Post-surgical patients

  • Indwelling devices (catheters, IVs)

  • Breaks in skin integrity

  • Poor oxygenation/impaired circulation

Chronic & Acute Disease

• Examples:

  • Diabetes mellitus

  • Adrenal insufficiency

  • Renal failure

  • Hepatic failure

  • Chronic lung disease

Lifestyle & Population Factors

• Examples:

  • Inadequate hand hygiene

  • IV drug use

  • Unprotected sex

  • Poor nutrition

  • Smoking/excessive alcohol

  • Crowded living environments

Older Adults

• Concerns:

  • Decreased immune response

  • Increased use of invasive devices

  • Dementia (reduced self-care ability)

SECTION 2: Body's Defenses Against Infection

Line of Defense

• Primary (First) Line of Defense:

  • Components:

  • Intact skin (#1 physical barrier)

  • Mucous membranes

  • Respiratory cilia

  • Stomach acid (pH)

  • Normal flora

  • Tears/saliva/urine flow

• Secondary (Second) Line of Defense:

  • Components:

  • Inflammatory response

  • Phagocytic cells (neutrophils, macrophages)

  • Complement system

  • Interferons

  • Fever response

  • Note: Nonspecific (no memory).

• Tertiary (Third) Line of Defense:

  • Components:

  • Specific adaptive immunity: B-lymphocytes produce antibodies; T-lymphocytes mediate cellular immunity.

  • Immunoglobulins: IgA, IgD, IgE, IgG, IgM — provides permanent immunity but requires time.

SECTION 3: Inflammation

Definition of Inflammation

• Description: Inflammation is the body's natural immune response to harm — injuries, infections, or toxins — designed to protect tissues and initiate healing.

Types of Inflammation

• Acute Inflammation:

  • Description: Protective and temporary; characterized by heat, pain, redness, swelling as WBCs fight threats.

• Chronic Inflammation:

  • Description: Unhealthy; damages cells and contributes to diseases like arthritis, vasculitis, and heart disease.

The Inflammatory Response (Steps)

1. Pattern receptors on cell surfaces recognize harmful stimuli.

2. Inflammatory pathways are activated.

3. Inflammatory markers are released.

4. Inflammatory cells are recruited to the site.

Hypersensitivity Reaction

• Definition: Exaggerated immune responses to harmless antigens.

• Severity Levels:

  • Mild: Hives, itching, runny nose — treat with antihistamines.

  • Moderate: Urticaria, angioedema — corticosteroids.

  • Severe (Anaphylaxis): Throat swelling, difficulty breathing, rapid pulse — treated with EPINEPHRINE (adrenaline).

  • Common Triggers: Food, medication, pollen, venom.

Lab Values: Measuring Infection & Inflammation

SECTION 4: Stages of Infection & Assessment

Stages of Infection

Local vs. Systemic Infections

Assessment Findings

Systemic (Generalized) Signs

• Symptoms:

  • Fever; chills (rising temp) → diaphoresis (falling temp).

  • Increased pulse & respiratory rate.

  • Malaise, fatigue, anorexia, nausea/vomiting.

  • Abdominal cramping, diarrhea.

  • Enlarged lymph nodes.

Local Inflammatory Response Signs

• Symptoms:

  • Redness (erythema).

  • Warmth.

  • Edema.

  • Pain/tenderness.

  • Loss of function.

Types of Exudate

Diagnostic Procedures

• Gallium scan: Identifies WBC 'hot spots' at sites of inflammation.

• X-ray, CT scan, MRI: Detect infections, abscesses, lesions.

• Biopsy: Tissue analysis to confirm infection or malignancy.

SECTION 5: Infection Prevention & Nurse's Role

Health Care-Associated Infections (HAIs)

• Definition: Infections acquired while receiving care in a healthcare setting, most commonly occurring in the ICU.

  • Sources:

  • Exogenous: Outside client.

  • Endogenous: Client's own altered flora.

  • Common Sites:

  • Urinary tract (most common) — E. coli, S. aureus, enterococci.

  • Surgical wounds; respiratory tract; bloodstream.

Iatrogenic Infection

• Definition: HAI resulting from a diagnostic or therapeutic procedure.

Risk Factors

• Examples:

  • Poor hygiene.

  • Poor nutrition.

  • Smoking.

  • Alcohol use.

  • Stress.

Best Prevention

• Frequent and effective hand hygiene.

Hand Hygiene

• Recommendation:

  • At least 20 seconds for both hand sanitizer and handwashing.

  • If hands are visibly soiled, wash with soap and water (not hand sanitizer).

  • Key Fact: C. diff and norovirus are NOT effectively killed by hand sanitizer — always use soap and water for these pathogens.

Standard Precautions

• Definition: Review all types of precautions applied to all clients regardless of known diagnosis.

• Components include:

  • Hand Hygiene.

  • Personal Protective Equipment (PPE).

  • Respiratory Hygiene / Cough Etiquette.

  • Sharps Safety.

  • Environmental Cleaning.

  • Safe Waste Disposal.

National Patient Safety Goals (NPSGs) — Infection

• NPSG Goals:

  • 07.01.01: Hand Hygiene — Comply with CDC/WHO guidelines; set goals to improve compliance.

  • 07.03.01: MDROs — Implement evidence-based practices to prevent MDRO-related HAIs; educate staff & families.

  • 07.04.01: Central Line BSI — Use proven guidelines to prevent CLABSIs; perform surveillance.

  • 07.05.01: Surgical Site — Implement evidence-based practices to prevent SSIs; educate staff and patients.

  • 07.06.01: Urinary Catheter — Use proven guidelines to prevent CAUTIs; avoid unnecessary catheter use.

SECTION 6: Specific Infections

Urinary Tract Infection (UTI)

UTI Quick Reference

• Symptoms:

  • Dysuria, frequency, hematuria, pyuria, malodorous urine, low back pain.

• Common Organisms:

  • E. coli (most common), S. aureus, enterococci.

• Risk Factors:

  • Indwelling urinary catheter, short female urethra, previous UTI, diabetes, poor hygiene.

• Diagnosis:

  • Urine culture & sensitivity.

• Prevention:

  • Adequate fluid intake, sterile catheter technique, wipe front-to-back.

• Treatment:

  • Antimicrobial therapy + Phenazopyridine for dysuria relief.

UTI Medications

Pyelonephritis

Pyelonephritis Quick Reference

• Description: Serious kidney infection — bacteria (usually E. coli) ascending from the bladder.

• Symptoms:

  • High fever, chills, flank pain, nausea and vomiting.

• Risk Factors:

  • Diabetes, pregnancy, immunocompromised individuals.

• Prevention:

  • Early and complete UTI treatment; good hydration.

• Treatment:

  • May require hospitalization for IV antibiotics, hydration, and pain management.

• Complications:

  • Sepsis, long-term kidney damage.

MRSA (Methicillin-Resistant Staphylococcus aureus)

• Definition: Gram-positive cocci resistant to methicillin and many other antibiotics.

MRSA Quick Reference

• Symptoms:

  • Resembles spider bite or pimple — red, swollen, painful bump/boil; warm to touch; may contain pus or drainage.

• Risk Factors:

  • Hospital patients, crowded settings, contact sports, weakened immune system.

• Diagnosis:

  • Culture & sensitivity (obtain BEFORE starting antibiotics).

• Precautions:

  • Contact Precautions.

• Prevention:

  • Good hygiene, screening & decolonization, antibiotic stewardship, disinfecting surfaces.

• Treatment:

  • Vancomycin OR Linezolid; monitor therapeutic drug levels.

MRSA Medications — Nursing Considerations

Cellulitis

Cellulitis Quick Reference

• Description: Bacterial skin infection of deep dermis & subcutaneous tissue — caused by S. aureus or Streptococcus.

• Symptoms:

  • Redness, warmth, edema, tenderness, fever.

• Risk Factors:

  • Poor circulation, diabetes, chronic skin infections, obesity, IV drug use.

• Diagnosis:

  • CBC, wound culture & sensitivity, ESR.

• Treatment:

  • Antibiotic therapy based on culture & sensitivity; wound care with aseptic technique.

• Prevention:

  • Maintain intact skin integrity, good hygiene, moisturize skin, clean open wounds.

SECTION 7: Quick Review & Key Concepts

Key Terms to Know