11.2 Infection Prevention & Isolation Precautions

The Chain of Infection

Infection requires six linked elements; breaking any single link prevents transmission — which is the logic behind every precaution you apply.

1. Infectious agent — bacteria, virus, fungus, parasite (killed or weakened by antibiotics, antisepsis, sterilization).
2. Reservoir — where the organism lives: people, water, equipment, soil (controlled by cleaning, disinfection, water management).
3. Portal of exit — how it leaves: respiratory secretions, blood, urine, wounds (controlled by covering coughs and wounds, containment).
4. Mode of transmission — contact (direct/indirect, the most common), droplet, airborne, vector, vehicle (broken by hand hygiene, PPE, isolation).
5. Portal of entry — how it enters the next host: mucous membranes, non-intact skin, invasive devices (broken by aseptic technique, catheter care).
6. Susceptible host — the elderly, immunocompromised, malnourished, or device-bearing patient (protected by vaccines, nutrition, device removal, glycemic control).

Hand Hygiene

Hand hygiene is the single most effective infection-prevention practice. The WHO "My Five Moments for Hand Hygiene" frame when to perform it:

• Moment 1: Before touching the patient
• Moment 2: Before a clean/aseptic procedure (e.g., dressing change, line access)
• Moment 3: After body-fluid exposure risk
• Moment 4: After touching the patient
• Moment 5: After touching the patient's surroundings (bed rails, tray table, monitors)

Alcohol-based hand rub (ABHR) is the default for routine decontamination when hands are not visibly soiled — rub until dry, about 20 seconds. Soap and water is mandatory when hands are visibly soiled and for spore-forming or non-enveloped organisms — classically Clostridioides difficile and norovirus — because alcohol does not inactivate spores. Wash with friction for at least 20 seconds (15–20 is taught by CDC), covering all surfaces. Other exam points: keep nails short and natural (no artificial nails in direct care), cover skin breaks, and perform hand hygiene before donning and after removing gloves — gloves are not a substitute.

Standard Precautions

Standard precautions apply to every patient, every time, regardless of known infection status, because any patient may harbor transmissible organisms. They include hand hygiene; gloves for anticipated contact with blood, body fluids, non-intact skin, or mucous membranes; gown, mask, and eye protection when splashes or sprays are anticipated; respiratory hygiene/cough etiquette; safe sharps handling (never recap by two-handed technique, never pass hand-to-hand); and proper equipment reprocessing and linen handling.

Transmission-Based Precautions

Added to standard precautions when a specific organism requires more.

Pearl: localized zoster in an immunocompetent host = standard precautions plus covering lesions; disseminated zoster or zoster in an immunocompromised host = airborne + contact. Meningococcal meningitis needs droplet precautions only for the first 24 hours of effective antibiotic therapy.

Donning and Doffing PPE

• Donning order: gown → mask/respirator → goggles or face shield → gloves (gloves pulled over gown cuffs). Hand hygiene first.
• Doffing order: gloves → goggles/face shield → gown → mask (removed after leaving an airborne room), then hand hygiene. Gloves are removed first because they are the most contaminated; the mask comes off last to protect the airway during removal of other items. Doff slowly, touching only the inside of contaminated items, and perform hand hygiene immediately if any bare skin touches a contaminated surface.

Multidrug-Resistant Organisms (MDROs)

Know the big four: MRSA (methicillin-resistant Staphylococcus aureus — treated with vancomycin or alternatives), VRE (vancomycin-resistant Enterococcus), ESBL producers (extended-spectrum beta-lactamase gram-negatives resistant to most penicillins/cephalosporins), and CRE (carbapenem-resistant Enterobacterales, resistant to last-line carbapenems). All are managed with contact precautions, dedicated equipment, meticulous hand hygiene, and antimicrobial stewardship. MDRO transmission in hospitals is overwhelmingly via the transiently contaminated hands of healthcare workers — hence the exam's fixation on hand hygiene.

Device- and Procedure-Associated Infection Bundles

CLABSI (central line–associated bloodstream infection) bundle:

• Hand hygiene before line access
• Maximal sterile barrier at insertion: cap, mask, sterile gown, sterile gloves, full-body drape
• Chlorhexidine (>0.5% in alcohol) skin antisepsis, scrubbed and allowed to dry
• Optimal site selection — subclavian preferred; avoid the femoral site in adults
• Daily review of line necessity with prompt removal — the single most powerful element
• Scrub the hub/needleless connector before each access; change transparent dressings every 7 days (gauze every 2 days) or when soiled

CAUTI (catheter-associated urinary tract infection) bundle: insert only for appropriate indications using aseptic technique and the smallest feasible catheter; maintain a closed drainage system with unobstructed flow; secure the catheter; keep the bag below the bladder and off the floor; perineal hygiene; and daily necessity review with early removal.

VAP (ventilator-associated pneumonia) bundle: elevate the head of bed 30–45°; daily sedation interruption and spontaneous breathing trial to shorten ventilator days; regular oral care (many protocols use chlorhexidine); subglottic secretion drainage when available; peptic ulcer and DVT prophylaxis as appropriate.

SSI (surgical site infection) prevention: prophylactic antibiotics within 60 minutes before incision (120 minutes for vancomycin and fluoroquinolones); remove hair with clippers, never a razor; perioperative normothermia and serum glucose control (commonly <180 mg/dL); sterile technique and appropriate skin prep.

Neutropenic Precautions vs. Protective (Reverse) Isolation

Neutropenic precautions protect the profoundly immunosuppressed patient — typically absolute neutrophil count (ANC) <500 cells/mm³ (severe neutropenia) — from environmental organisms. Key elements: private room, strict hand hygiene, no fresh flowers or standing water in plants, no raw or undercooked foods (a low-microbial/neutropenic diet avoids unpasteurized products and unwashed produce), no live plants, screening visitors for illness, and a mask on the patient when leaving the room. Modern guidance frames this as standard precautions with added environmental protections rather than true "reverse isolation"; full protective environments with positive-pressure HEPA filtration are reserved for hematopoietic stem-cell transplant patients. Report fever urgently: a single oral temperature ≥38.3°C (101°F) or ≥38.0°C (100.4°F) sustained over 1 hour in a neutropenic patient is a medical emergency — obtain cultures and start broad-spectrum antibiotics within 1 hour.

Safe Injection Practices (CDC One & Only Campaign)

• One needle, one syringe, one patient — every time. Needles and syringes are single-patient, single-use even if the needle is changed.
• Single-dose vials are for one patient; multi-dose vials should be dedicated to a single patient whenever possible and are discarded per policy (typically 28 days after first puncture unless manufacturer states otherwise).
• Never use the same syringe to re-enter a vial, never administer medications from the same syringe to multiple patients, and never use IV solution bags as a common supply for multiple patients. Unsafe injection practices have caused real HBV/HCV outbreaks — the exam treats them as never events.

Needlestick / Bloodborne Pathogen Exposure Protocol

1. Immediately wash the site with soap and water (flush mucous membranes with water/saline); do not squeeze aggressively or apply caustic agents.
2. Report at once to occupational/employee health and your supervisor; complete an exposure report — time matters.
3. Test the source patient (with consent per state law) for HIV, hepatitis B surface antigen, and hepatitis C antibody; draw baseline labs on the exposed worker.
4. HIV post-exposure prophylaxis (PEP) is indicated based on risk and must begin within 72 hours — ideally within 2 hours — and continues 28 days.
5. Hepatitis B: response depends on the worker's vaccination and antibody status; the unvaccinated or non-immune worker may receive hepatitis B immune globulin (HBIG) and begin the vaccine series. Hepatitis C: no PEP exists; serial HCV RNA testing detects early infection so direct-acting antivirals can cure it.
6. Follow-up testing and counseling per occupational health protocol. The HBV vaccine, offered free to at-risk employees under OSHA's Bloodborne Pathogens Standard, is the worker's best protection.