17.1 Infection Prevention & Control: Standard & Transmission-Based Precautions

Infection Prevention & Control: Standard & Transmission-Based Precautions

Core Clinical Principle: Infection Prevention and Control (IPC) is a fundamental nursing competency governed in Ireland by the Health Service Executive (HSE) Antimicrobial Resistance and Infection Control (AMRIC) programme. Registered Nurses must operate under a two-tiered system of precautions: Standard Precautions, applied universally to all patients at all times, and Transmission-Based Precautions (Contact, Droplet, and Airborne), added whenever a patient is confirmed or suspected to harbour transmissible pathogens.

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The Chain of Infection

Healthcare-associated infections (HCAIs) develop through a continuous, cyclical biological pathway known as the Chain of Infection. Breaking any single link in this chain prevents transmission and halts the spread of pathogens:

+-----------------------------------------------------------------------------+
|                           THE CHAIN OF INFECTION                            |
+-----------------------------------------------------------------------------+
|  1. CAUSATIVE ORGANISM  --> Bacteria, viruses, fungi, parasites, prions     |
|          v                                                                  |
|  2. RESERVOIR           --> Humans (patients/staff), water, medical devices |
|          v                                                                  |
|  3. PORTAL OF EXIT      --> Respiratory tract, blood, stool, broken skin    |
|          v                                                                  |
|  4. MODE OF TRANSMISSION--> Direct contact, indirect fomites, droplets, air |
|          v                                                                  |
|  5. PORTAL OF ENTRY     --> Mucous membranes, open wounds, invasive lines  |
|          v                                                                  |
|  6. SUSCEPTIBLE HOST    --> Immunocompromised, elderly, surgical patients   |
+-----------------------------------------------------------------------------+

Clinical Strategies to Break Each Link

1. Causative Organism: Rapid diagnostic microbiology, targeted antimicrobial stewardship, immunisation.
2. Reservoir: Environmental cleaning, safe water management, prompt waste disposal, single-room isolation.
3. Portal of Exit: Respiratory etiquette (cough hygiene), waterproof wound dressings, safe handling of bodily fluids.
4. Mode of Transmission: Hand hygiene (WHO 5 Moments), personal protective equipment (PPE), physical distancing, dedicated patient equipment.
5. Portal of Entry: Aseptic Non-Touch Technique (ANTT) during invasive device insertion and maintenance, intact skin protection, secure catheter care.
6. Susceptible Host: Optimising nutritional status, treating underlying comorbidities, administering indicated vaccinations (e.g., Influenza, Pneumococcal, COVID-19), early removal of invasive devices (urinary catheters, peripheral IV cannulae).

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Standard Precautions

Standard Precautions represent the baseline standard of care applied to ALL patients at ALL times, regardless of their perceived or documented infection status. Standard Precautions presume that every patient's blood, body fluids, secretions, excretions (excluding sweat), non-intact skin, and mucous membranes contain transmissible infectious agents.

The 10 Core Components of Standard Precautions

1. Hand Hygiene: Performed before and after every patient contact using the WHO 5 Moments.
2. Point-of-Care Risk Assessment (PCRA) & PPE Selection: Evaluating the anticipated clinical exposure before touching the patient, selecting gloves, aprons, fluid-repellent surgical masks (Type IIR), and eye protection based on the likelihood of blood or body fluid splashes.
3. Respiratory Hygiene & Cough Etiquette: Providing tissues, masks, and hand sanitiser to coughing patients; covering mouth and nose with flexed elbow or tissue during coughing.
4. Safe Injection Practices & Sharps Safety: Utilizing safety-engineered needles, never re-sheathing needles manually, and disposing of sharps immediately at point-of-use into certified rigid containers.
5. Environmental Cleaning: Routine cleaning and disinfection of ward surfaces, bed frames, call bells, and sanitary facilities using neutral detergents and hospital-grade disinfectants.
6. Decontamination of Patient Care Equipment: Cleaning and disinfecting reusable medical equipment between patients according to Spaulding's Classification:
   • Critical items (entering sterile tissue or vascular system, e.g., surgical instruments): Require complete sterilization.
   • Semi-critical items (contacting mucous membranes or non-intact skin, e.g., endoscopes, respiratory circuits): Require high-level disinfection.
   • Non-critical items (contacting intact skin, e.g., BP cuffs, stethoscopes, commodes): Require intermediate to low-level disinfection with detergent wipes or 70% isopropyl alcohol wipes.
7. Safe Handling of Linen & Textiles: Rolling (not shaking) soiled linen away from uniform; placing non-soiled linen in white canvas bags and blood/body-fluid soiled linen into red water-soluble alginate bags enclosed in an outer impermeable bag.
8. Safe Management of Healthcare Waste: Segregating waste at source into domestic (black/clear), clinical/risk (yellow), or cytotoxic (purple) receptacles.
9. Safe Handling of Biological Specimens: Placing specimens in leak-proof primary containers sealed inside secondary biohazard bags with external laboratory requisition forms.
10. Patient Placement & Bed Spacing: Maintaining at least 1 metre (ideally 1.5–2 metres) of clearance between hospital beds to prevent cross-contamination.

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Transmission-Based Precautions

Transmission-Based Precautions are initiated in addition to Standard Precautions whenever a patient is infected or colonised with clinically significant pathogens transmitted via contact, droplet, or airborne routes.

+-----------------------------------------------------------------------------+
|                   TRANSMISSION-BASED PRECAUTIONS MATRIX                     |
+-------------------+--------------------+--------------------+---------------+
| CATEGORY          | PATHOGEN EXAMPLES  | PPE REQUIRED       | ROOM TYPE     |
+-------------------+--------------------+--------------------+---------------+
| CONTACT           | CPE, MRSA, VRE,    | Disposable plastic | Single room   |
| PRECAUTIONS       | C. diff, Norovirus | apron & gloves on  | (ensuite      |
|                   | Scabies            | room entry         | preferred)    |
+-------------------+--------------------+--------------------+---------------+
| DROPLET           | Influenza, Mumps,  | Fluid-repellent    | Single room   |
| PRECAUTIONS       | Pertussis, N.      | surgical mask      | or cohorting; |
|                   | meningitidis       | (Type IIR) + visor | standard air  |
+-------------------+--------------------+--------------------+---------------+
| AIRBORNE          | Pulmonary TB,      | Fit-tested FFP2 /  | Negative      |
| PRECAUTIONS       | Measles, Varicella | FFP3 particulate   | pressure room |
|                   | zoster (shingles)  | respirator mask    | (AIIR, 6-12ACH)|
+-------------------+--------------------+--------------------+---------------+

1. Contact Precautions

• Transmission Mechanism: Direct physical transfer between host and susceptible person (e.g., patient turning, bathing), or indirect contact via contaminated fomites, bed rails, blood pressure cuffs, or commodes.
• Key Organisms: Carbapenemase-Producing Enterobacterales (CPE), Methicillin-Resistant Staphylococcus aureus (MRSA), Vancomycin-Resistant Enterococci (VRE), Clostridioides difficile, Extended-Spectrum Beta-Lactamases (ESBL), Norovirus, and Scabies.
• Accommodation: Single room with dedicated ensuite facilities. If single rooms are exhausted, cohorting requires IPC team authorisation.
• PPE Mandate: Don disposable plastic apron and non-sterile gloves immediately upon entering the patient room; remove and discard into yellow clinical waste bins and perform hand hygiene before exiting the room.
• Equipment Controls: Dedicated single-patient equipment (commode, sphygmomanometer, pulse oximeter probe, stethoscope). If sharing is unavoidable, thoroughly disinfect using an approved agent before use on another patient.

2. Droplet Precautions

• Transmission Mechanism: Large respiratory droplets (>5 micrometres in diameter) generated during coughing, sneezing, talking, or airway suctioning. Droplets travel through the air for short distances (typically 1 to 2 metres) before settling onto mucosal surfaces (eyes, nose, mouth) of a susceptible host.
• Key Organisms: Influenza A and B, Bordetella pertussis (whooping cough), Neisseria meningitidis (meningococcal meningitis/sepsis), Rubella, Mumps, and Group A Streptococcus pharyngitis.
• Accommodation: Single room with standard neutral/positive airflow, door closed. Cohorting is permitted only among patients confirmed with the identical strain.
• PPE Mandate: Don a Type IIR fluid-repellent surgical mask upon entering the room or whenever within 1–2 metres of the patient. Add eye protection (visor, goggles) if there is risk of respiratory secretions spraying or splashing.
• Patient Transport: If transport outside the room is essential, the patient must wear a surgical mask.

3. Airborne Precautions

• Transmission Mechanism: Droplet nuclei (evaporated droplets <5 micrometres in diameter) or dust particles containing viable pathogens that remain suspended in ambient air currents for hours and disperse widely across room ventilation systems.
• Key Organisms: Infectious Pulmonary or Laryngeal Tuberculosis (Mycobacterium tuberculosis), Measles (Rubeola), Varicella zoster (Chickenpox), Disseminated Herpes Zoster, and viral haemorrhagic fevers.
• Accommodation: Airborne Infection Isolation Room (AIIR) with dedicated negative-pressure ventilation relative to corridors (pressure differential of at least −2.5 Pascals), achieving 6 to 12 air changes per hour (ACH), with exhaust air discharged directly outside or HEPA-filtered.
• PPE Mandate: All healthcare staff entering the room must wear a fit-tested FFP2 or FFP3 particulate respirator mask (filtering at least 94% or 99% of airborne particles respectively). Check facial seal integrity on every donning.
• CRITICAL DOFFING RULE: The FFP2/FFP3 respirator mask must NEVER be removed inside the airborne isolation room. Doff the apron and gloves inside the room, perform hand hygiene, exit the room, close the door, and then remove the respirator mask in the anteroom or outer corridor, followed by immediate hand hygiene.

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Carbapenemase-Producing Enterobacterales (CPE)

In October 2017, the National Public Health Emergency Team (NPHET) and Department of Health declared Carbapenemase-Producing Enterobacterales (CPE) a National Public Health Emergency in Ireland. Enterobacterales (E. coli, Klebsiella pneumoniae, Enterobacter cloacae) are normal intestinal commensals. When they acquire plasmid-mediated carbapenemase enzymes (e.g., OXA-48, KPC, NDM, VIM), they become resistant to carbapenems (meropenem, ertapenem, imipenem)—the ultimate "last-line" broad-spectrum beta-lactam antibiotics.

HSE National CPE Screening Criteria

Every adult patient admitted to an Irish acute hospital must undergo an assessment for CPE risk. An admission rectal swab (or fresh faecal sample) must be collected from patients meeting any of the following high-risk criteria:

1. Inpatient admission to any Irish or overseas hospital for at least one night in the preceding 12 months.
2. Transfer directly from another acute hospital, rehabilitation facility, or long-term nursing care facility.
3. Known prior colonisation or infection with CPE.
4. Household contact or close contact with a known CPE-colonised individual.
5. Regular attendees at oncology, haematology, or renal dialysis services.

Clinical Management Protocol for Suspected or Confirmed CPE

• Pre-emptive Isolation: Patients fulfilling screening criteria must be placed in pre-emptive Contact Isolation in a single room with ensuite facilities while awaiting laboratory PCR/culture screening results.
• Specimen Collection: Collect a rectal swab ensuring visible faecal staining on the swab tip; transport immediately in Amies transport medium to microbiology.
• Barrier Nursing: Don disposable apron and gloves on room entry; change gloves and wash hands between clinical tasks.
• Dedicated Facilities: Patient must have a dedicated ensuite toilet or dedicated commode marked with their identification; shared ward commodes are strictly prohibited.
• Environmental Cleaning: Daily and terminal cleaning with a chlorine-releasing agent (1,000 ppm available chlorine) or hydrogen peroxide vaporisation. CPE persists on dry hospital surfaces for months.
• Clearance Policy: In Ireland, CPE colonisation is considered lifelong for infection control purposes. Patients are never considered "cleared" by negative repeat swabs; single-room contact precautions remain mandatory on all subsequent admissions.

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Clostridioides difficile Infection (CDI)

Clostridioides difficile is an anaerobic, Gram-positive, spore-forming bacillus that causes severe toxin-mediated pseudomembranous colitis, toxic megacolon, and septic shock. CDI typically follows broad-spectrum antimicrobial exposure (especially third-generation cephalosporins, fluoroquinolones, co-amoxiclav, or clindamycin) that disrupts protective colonic microflora.

Pathological Spore Resilience

C. difficile produces hardy endospores that survive on dry inanimate surfaces for months. These endospores are resistant to heat, drying, and chemical disinfectants, including standard alcohol hand gels and chlorhexidine.

[!CAUTION] The Soap and Water Mandate: Alcohol-Based Hand Rub (ABHR) is completely ineffective against bacterial endospores. When caring for any patient with confirmed or suspected Clostridioides difficile, or any patient with unexplained acute watery diarrhoea, healthcare workers MUST wash hands using liquid soap and warm running water for at least 40 to 60 seconds. Mechanical friction and running water physically detach and flush spores off epidermal ridges.

Environmental Decontamination for C. difficile

• Standard quaternary ammonium detergents and alcohol wipes do not kill spores.
• Decontamination requires a sporicidal agent: a chlorine-releasing agent (sodium hypochlorite) diluted to 1,000 parts per million (ppm) available chlorine (0.1% solution), or an approved accelerated hydrogen peroxide or peracetic acid formulation.
• Commodes must be cleaned immediately after each use using a sporicidal wipe or chlorine solution.

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Clinical Traps & OSCE Safety Pearls

• OSCE Trap 1: Doffing FFP3 Masks Inside the Patient Room. In airborne stations (e.g., suspected TB), removing your respirator mask inside the room causes immediate inhalation of suspended droplet nuclei. You must exit the room, close the door, and doff the respirator outside in the anteroom or corridor.
• OSCE Trap 2: Using Alcohol Gel for C. diff or Norovirus. In practical examinations, selecting ABHR after managing a patient with active diarrhoea is an automatic critical failure. You must state: "I am washing my hands with liquid soap and water because alcohol rub does not kill Clostridioides difficile spores."
• OSCE Trap 3: Omitting Eye Protection During High-Risk Procedures. Wearing only a mask and gloves during airway suctioning or wound irrigation of a contact/droplet patient violates Standard Precautions. Whenever splashing is anticipated, eye protection (goggles or full-face visor) is mandatory.
• OSCE Trap 4: Attempting to "De-isolate" a CPE-Positive Patient. In Ireland, a patient with a history of CPE carriage cannot be released from contact isolation based on three negative follow-up swabs. The HSE AMRIC protocol classifies CPE carriage as persistent for hospital IPC purposes.