Sterilization & Disinfection in Healthcare

Key Definitions

Term	Definition
Sterilization	Destruction of ALL microbial life, including bacterial spores
Disinfection	Elimination of most pathogenic organisms (not necessarily spores)
Antisepsis	Disinfection applied to living tissue/skin
Decontamination	Reduction of microbial load to safe levels on objects/surfaces
Cleaning	Physical removal of organic/inorganic material — always the first step

Cleaning must precede disinfection and sterilization; organic material shields microorganisms and inactivates chemical agents. (CDC Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008, p. 8)

Spaulding Classification — Levels of Care Required

The Spaulding system categorizes patient-care items by infection risk:

Category	Definition	Required Process	Examples
Critical	Enters sterile tissue or vascular system	Sterilization	Surgical instruments, cardiac catheters, implants
Semi-critical	Contacts mucous membranes or non-intact skin	High-level disinfection (minimum)	Endoscopes, laryngoscope blades, respiratory therapy equipment
Non-critical	Contacts intact skin only	Low- or intermediate-level disinfection	Blood pressure cuffs, stethoscopes, bedpans

Levels of Disinfection

High-Level Disinfection (HLD)

Kills all organisms except large numbers of bacterial spores
Required for semi-critical items
Agents: glutaraldehyde, ortho-phthalaldehyde (OPA), hydrogen peroxide, peracetic acid, chlorine compounds

Intermediate-Level Disinfection

Kills Mycobacterium tuberculosis, vegetative bacteria, most viruses and fungi; not spores
Agents: alcohols, iodophors, phenolics

Low-Level Disinfection

Kills most vegetative bacteria, some fungi and viruses; not mycobacteria or spores
Agents: quaternary ammonium compounds, low-concentration chlorine

Chemical Disinfectants — Quick Reference

Agent	Level	Key Uses	Notes
Glutaraldehyde (2%)	High	Endoscopes, heat-sensitive instruments	Requires adequate contact time (20–45 min); toxic fumes
OPA (0.55%)	High	Endoscopes	Superior mycobactericidal activity; stains protein gray
Hydrogen peroxide (3–6%)	High/Intermediate	Surfaces, contact lenses	Environmentally friendly
Peracetic acid	High/Sterilant	Endoscopes (Steris system)	Rapid action; no toxic residues
Alcohols (70–90% ethanol/isopropanol)	Intermediate	Skin antisepsis, surfaces	No sporicidal activity; flammable
Chlorine/hypochlorite	High–Low (concentration-dependent)	Blood spills, surfaces, C. diff	1:10 bleach for blood spills; sporicidal at high concentrations
Iodophors	Intermediate	Skin antisepsis, surfaces	Less irritating than iodine
Phenolics	Intermediate–Low	Environmental surfaces	Not for use in neonatal settings
Quaternary ammonium compounds (QACs)	Low	Non-critical surfaces, housekeeping	Limited spectrum; inactivated by soaps
Formaldehyde	High	Rarely used due to toxicity	Carcinogen; limited clinical use

Sterilization Methods

Physical Methods

Method	Mechanism	Application	Notes
Steam (Autoclave)	Moist heat (121°C/132°C)	Most surgical instruments, textiles	Gold standard; rapid, cheap, non-toxic; cannot be used for heat/moisture-sensitive items
Dry Heat	Oxidation (160–170°C)	Glassware, oils, powders	Longer cycles; no moisture damage
Radiation (gamma/electron beam)	DNA damage	Single-use devices (industrial)	Not used in clinical settings

Chemical/Gas Methods

Method	Agent	Application	Notes
Ethylene oxide (ETO)	Alkylating agent	Heat/moisture-sensitive devices (endoscopes, plastics)	Long aeration time needed; carcinogenic; excellent penetration
Hydrogen peroxide gas plasma	Free radical oxidation	Heat/moisture-sensitive instruments	Short cycle (~55 min); no toxic residues; cannot process cellulose or long narrow lumens
Peracetic acid (liquid)	Oxidation	Immersible instruments (endoscopes)	Point-of-use system (Steris); no sterilant storage needed
Vaporized H₂O₂ (VHP)	Oxidation	Room decontamination, heat-sensitive items	Effective against spores
Low-temperature steam + formaldehyde	Alkylation	Heat-sensitive items	Common in Europe

Practical Workflow

Receive soiled instrument
        ↓
  1. CLEAN (manual scrubbing / ultrasonic / washer-disinfector)
        ↓
  2. INSPECT & TEST (check for integrity, residual soil)
        ↓
  3. PACKAGE (if sterilization required)
        ↓
  4. DISINFECT or STERILIZE (based on Spaulding classification)
        ↓
  5. STORE properly (maintain sterility/cleanliness until use)

Special Considerations

Endoscopes

Flexible endoscopes are the most common source of instrument-related infection outbreaks
Require high-level disinfection at minimum; sterile water for final rinse preferred
Drying is critical — residual moisture promotes biofilm and waterborne pathogen growth
Endovaginal/transrectal probes: probe cover does not replace HLD (covers frequently leak)

Clostridioides difficile (C. diff)

Spores are resistant to most disinfectants including alcohols and QACs
Use sodium hypochlorite (bleach) or EPA-registered sporicidal agents for environmental decontamination

Prions (CJD)

Extremely resistant — survive routine sterilization
Require prolonged autoclaving (134°C, 18 min) or sodium hydroxide/hypochlorite treatment
Single-use instruments preferred for high-risk neurosurgical procedures

Immediate-Use Steam Sterilization (IUSS / "Flash")

Reserved for emergency situations only — not a substitute for standard sterilization
Associated with increased SSI risk when used routinely

Monitoring Sterilization Efficacy

Monitor Type	Purpose	Examples
Biological indicators (BIs)	Confirm kill of resistant spores (gold standard)	Geobacillus stearothermophilus (steam), Bacillus atrophaeus (ETO)
Chemical indicators (CIs)	Confirm exposure to sterilizing conditions	Color-changing tape, integrators
Mechanical indicators	Record time, temperature, pressure	Autoclave printout, gauges

All three monitoring types should be used together for complete quality assurance.

Primary source: CDC Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008 (p. 8); Rutala WA, Weber DJ. Disinfection, Sterilization, and Antisepsis: An Overview. Am J Infect Control 2019;47:A3–A9.

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