Principles of Infection Prevention and Control – Vocabulary Review

Learning Objectives

• Define health care–associated infections (HAIs) and recognize their frequency in modern clinical practice.

  • Roughly 4\% of hospitalized patients develop an HAI.

• Understand the importance of infection prevention in respiratory care.

• Identify the three elements that must be present for transmission of infection in a health-care setting.

• List patient-related risk factors that increase the probability of hospital-acquired infection.

• State the three major routes through which pathogens spread from human sources in the health-care environment.

• Describe aerosol transmission and the continuum between droplets and droplet nuclei.

• Summarize practical strategies for curbing infection spread in hospitals.

• Select and apply chemical disinfectants appropriately when processing respiratory-care equipment.

• Outline equipment-handling procedures that limit pathogen dissemination.

• Recognize situations that demand special infection-control measures.

• Determine when and how to use personal protective equipment (PPE).

• Explain how infection-control surveillance programs function.

Health-Care–Associated Infections (HAIs)

• Definition

  • Any infection that develops during the course of medical treatment.

  • Sub-categories by point of origin:

  • Community-onset: develops outside the hospital.

  • Hospital-onset / nosocomial: originates \ge 48 hours after admission.

• Incidence & Impact

  • Occur in about 4\% of admitted patients.

  • Lead to prolonged stays, increased costs, higher morbidity/mortality, and reputational harm.

• Institutional Response

  • Infection Prevention (IP) programs are tasked with lowering HAI risk for patients, staff, and visitors by “breaking the chain of infection.”

  • Multidisciplinary approach: clinicians, nurses, respiratory therapists, environmental services, administration.

Elements Required for Infection Transmission

1. Source (reservoir) of pathogens.

2. Susceptible host.

3. Route (mode) of transmission.

Sources (Reservoirs) of Pathogens

• Human Reservoirs

  • Patients, visitors, health-care workers.

  • Endogenous flora (e.g., skin, upper airway, GI tract) serve as major donor microbes.

• Inanimate Reservoirs

  • Contaminated medical equipment, linens, medications, surfaces.

  • Patients quickly contaminate the local environment (bed rails, over-bed tables, call buttons).

Susceptible Hosts

• Host susceptibility varies according to immune competence, comorbidities, and invasive devices.

• High-risk factors:

  • Poorly controlled diabetes mellitus.

  • Extremes of age (neonates; elder adults).

  • Immunodeficiency (e.g., HIV infection, chemotherapy-induced neutropenia).

  • Invasive lines and tubes: IV catheters, endotracheal tubes, urinary catheters.

• Significance: Understanding host factors guides targeted prevention strategies such as vaccination, prophylaxis, and device-bundle implementation.

Modes of Transmission

1. Contact (direct & indirect) – most common.

2. Droplet – large-particle respiratory sprays.

3. Airborne – small droplet nuclei that remain suspended.

Contact Transmission

• Direct contact

  • Physical person-to-person transfer (e.g., turning or bathing patient without gloves).

  • Less frequent in hospitals compared with indirect.

• Indirect contact

  • Transfer via contaminated intermediate objects or personnel (fomites).

  • Examples: stethoscope, blood-pressure cuff, improperly disinfected bronchoscope.

Respiratory Transmission

• Droplet

  • Particles > 5 µm travel short distances (≈ 1 m) and settle on surfaces.

  • Representative agents: Neisseria meningitidis, influenza virus.

• Airborne

  • Droplet nuclei \le 5 µm remain suspended for hours, dispersing over long distances.

  • Classic pathogens: Mycobacterium tuberculosis, measles virus.

• Continuum Concept: Droplets may partially desiccate, shrinking into droplet nuclei capable of airborne behavior—underlines the need for flexible precautions.

Infection-Prevention Strategies

Creating a Safe Culture

• Leadership at all levels must foster a shared commitment to patient & worker safety.

• Everyone empowered to “stop the line” if best practices are threatened.

• Comprehensive Unit-Based Safety Program (CUSP) promotes frontline involvement.

Maintaining a Healthy Workforce

• Sick workers jeopardize care delivery & patient safety.

• Measures include:

  • Immunizations (influenza, HepB, MMR, varicella, Tdap).

  • Chemoprophylaxis (e.g., oseltamivir during flu outbreaks).

  • OSHA standards govern employee safety & reporting.

Eliminating the Source of Pathogens

• Standard measures encompass thorough environmental cleaning & equipment reprocessing.

• Two tactical clusters:

  1. General sanitation (routine surface disinfection, waste disposal).

  2. Specialized equipment processing (cleaning, disinfection, sterilization schedules).

• Definitions

  • Bactericidal: kills bacteria.

  • Bacteriostatic: inhibits bacterial growth.

  • Sporicidal: destroys spores.

  • Virocidal: inactivates viruses.

Interrupting Routes of Transmission

• Adherence to guidance from HICPAC & CDC.

• Key interventions: hand hygiene, PPE compliance, safe injection practices, environmental controls.

Standard Precautions

• Baseline strategy for all patients regardless of diagnosis.

• Components:

  • Hand hygiene before & after patient/environment contact.

  • Gloves when touching blood, body fluids, mucous membranes.

  • Mask, eye protection/face shield during procedures that generate splashes/sprays.

  • Respiratory hygiene/cough etiquette.

  • Gowns/aprons for procedures with expected clothing contamination.

  • Use of source-control masks for coughing patients.

Transmission-Based Precautions (Used in Addition to Standard)

Contact Precautions

• Single room preferred; if unavailable, cohort with same pathogen.

• Wear gown & gloves upon room entry.

• Dedicated equipment or disinfect between uses.

Droplet Precautions

• Surgical mask within 1 m of patient.

• Patient wears mask during transport.

Airborne Infection Isolation (AII)

• Pathogens: M. tuberculosis, varicella, rubeola.

• Requirements:

  • Negative-pressure room with \ge 2 air exchanges/hr.

  • HEPA filtration of exhaust air.

  • NIOSH-approved N-95 (or higher) respirators for staff.

Protective Environment

• For highly immunocompromised (e.g., allogeneic stem-cell transplant).

• Engineering controls:

  • HEPA-filtered supply air.

  • Positive pressure relative to corridor.

  • \ge 12 air changes/hr.

  • Sealed room envelope; dust reduction strategies; ban on flowers/plants.

Special Population: Cystic Fibrosis (CF)

• CF patients prone to recurrent infections, bronchiectasis, and multidrug-resistant organisms.

• Universal contact precautions in all settings.

• Patients should wear surgical masks outside their rooms.

Transport of Infected Patients

• Limit movement whenever feasible.

• During necessary transport:

  • Patient dons appropriate barrier (mask, gown).

  • Manual resuscitator must have expiratory-side filter for respiratory-isolation patients.

Device-Related HAIs & Prevention Bundles

• Common device infections:

  • Ventilator-Associated Pneumonia (VAP).

  • Catheter-Related Bloodstream Infection (CRBSI/CLABSI).

  • Catheter-Associated Urinary Tract Infection (CAUTI).

• Prevention Bundles: sets of evidence-based actions implemented together (e.g., head-of-bed elevation 30^{\circ}–45^{\circ} plus daily sedation holidays for VAP).

• Demonstrated to significantly lower HAI rates.

Disinfection & Sterilization of Equipment

Cleaning (Step 1)

• Physical removal of soil; prerequisite for all further processing.

• Use soaps/detergents compatible with device.

• Noncritical items (commodes, IV pumps, ventilator surfaces) must be cleaned & low-level disinfected between patients.

Disinfection (Step 2)

• Destroys vegetative pathogens but not spores.

• Methods:

  • Heat: pasteurization (e.g., 70–75 °C for 30 min).

  • Chemical: immersion in EPA-registered disinfectants for specified dwell time.

Chemical Disinfection Nuances

• Total immersion ensures internal & external surfaces treated.

• Manufacturer instructions dictate concentration, temperature, exposure time, and rinsing.

Sterilization (Step 3)

• Destroys all microorganisms, including spores.

• Physical: steam under pressure (autoclave) — typically 121 °C, 15 psi, 15 min.

• Chemical: low-temperature options for heat-sensitive devices (ETO gas, hydrogen-peroxide plasma).

Equipment-Handling Procedures

• In-use maintenance: periodic changing of ventilator circuits, suction tubing according to policy.

• Reusable processing: adherence to Spaulding classification (critical, semi-critical, non-critical).

• Single-patient disposables: eliminate reprocessing but raise cost & waste issues.

High-Risk Respiratory Devices

• Nebulizers (large- & small-volume) — can aerosolize bacteria.

• Ventilator circuits — condensate fosters growth; HEPA filters on expiratory limb reduce contamination.

• Bag-valve-mask & suction equipment — surfaces become colonized; require cleaning/disinfection.

• Oxygen therapy & pulmonary-function devices — mouthpieces, humidifiers must be disinfected/changed.

Reprocessing Reusable Equipment

• Decision variables:

  • Manufacturer’s Instructions for Use (IFU).

  • Infection-risk category.

  • Device material & geometry.

  • Available institutional resources.

  • Cost (labor + supplies).

Bronchoscope Reprocessing

• High contamination risk due to mucosal contact.

• Transmission drivers:

  • Failure to perform meticulous manual cleaning before high-level disinfection.

  • Malfunctioning automated endoscope reprocessors (AERs).

  • Instrument design flaws (e.g., narrow lumens that trap debris).

Disposable Equipment Considerations

• Pros: eliminates cross-contamination risk, saves reprocessing labor.

• Cons: increased cost, variable quality, environmental burden.

• Re-use of intended single-use items may breach regulations and compromise integrity.

• Fluid & medication precautions: single-dose vials when possible; never top-off humidifiers.

Surveillance of HAIs

• Continuous monitoring of patients & staff to detect infection/colonization trends.

• Infection-Control Committee crafts policy; IP experts execute data collection and feedback.

• Common surveillance targets:

  • Hand-hygiene compliance.

  • Device-related infections (CLABSI, CAUTI, VAP/VAE).

Ventilator-Associated Events (VAE)

• Three-tier hierarchical surveillance construct:

  1. VAC – sustained \uparrow in daily minimum PEEP or FiO_2 \ge 2 calendar days after baseline stability.

  2. IVAC – VAC plus fever/hypothermia or leukocytosis/-penia and ≥ 4 days of new antibiotics.

  3. PVAP – IVAC with positive quantitative culture above threshold or purulent secretions plus culture growth below threshold.

• Purpose: provides objective, automatable metrics that capture a wider spectrum of ventilator complications than classic VAP alone.

• Limitation: may over- or under-detect true pneumonias; must be complemented by clinical judgment.

Practical Take-Home Points

• Meticulous hand hygiene remains the single most effective HAI countermeasure.

• AII rooms = negative pressure, whereas protective environments = positive pressure — memorize the difference for exams & clinical practice.

• Cleaning failure negates all downstream disinfection/sterilization — “dirty in, dirty out.”

• Device bundles succeed because each component targets a different link in the infection chain; partial compliance erodes benefit.

• Surveillance data are actionable only when fed back to frontline staff in a timely, comprehensible format.