Sterilization…

• Critical processes for safety in hospital/research facilities, validity of tests and infection control

  • Sterilization
  • Disinfection
• Cleaning


  General removal of debris (dirt, food, feces...) to reduce the amount of organic matter that contributes to proliferation of bacteria and viruses
• Disinfection


  Reducing the number of contaminating organisms to a level which is deemed no longer harmful to health
• Antiseptic


  A disinfectant applied to living tissue such as a wound on skin
• Sterilization


  The killing or removal of all organisms
• Dose


  The concentration of the killing agent and the length of time the agent is applied
• Decreasing order of innate resistance of microorganisms

  • Prions (Creutzfeldt-Jakob Disease)
  • Bacterial spores (Bacillus atrophaeus)
  • Coccidia (Cryptosporidium)
  • Mycobacteria (M. tuberculosis, M. terrae)
  • Nonlipid or small viruses (polio, coxsackie)
  • Fungi (Aspergillus, Candida)
  • Vegetative bacteria (S. aureus, P. aeruginosa)
  • Lipid or medium-sized viruses (HIV, herpes, hepatitis B)
• Levels of disinfection or sterilization

  • Prion reprocessing
  • Sterilization
  • Disinfection
  • High
  • Intermediate
  • Low
• Personal protective equipment for cleaning, disinfection, sterilization

  • Long sleeved impervious gown
  • Eyewear
  • Mask or mask with face shield
  • Gloves
  • Cap
  • Chemical goggles (when mixing or changing solution)
• Cleaning


  A soil removal process, contaminated surfaces increase potential for transmission of pathogens, difficult to quantify but a necessary pre-requisite to sterilization and disinfection
• Enzymatic detergent products


  • ENZYCLEAN Protease Enzyme Low Suds Detergent
  • ENZYCLEAN IV NE
  • ENZYCLEAN II LS Dual Enzyme Low Suds Detergent
  • ENZYCLEAN II Qual Enzyme Detergent
  • WEIMAN Dual enzymes detergents
• Methods to monitor environmental cleaning processes

  • Visual inspection (during, post cleaning)
  • Fluorescence (process measure)
  • Culturing
• Healthcare devices and equipment designated

  • Critical
  • Semi-critical
  • Non-critical
• Critical items


  Require sterilization, includes items that enter sterile tissue or the vascular system
• Semi-critical items


  Require high level disinfection or sterilization, includes items in contact with non-intact skin or mucous membranes
• Non-critical items


  Require low-level disinfection, includes items in contact only with intact skin
• Sterilization methods


  • Heat-dry/moist
  • Sterilant chemicals
  • Filtration
  • Radiation
• Dry heat sterilization


  Heat destroys microorganisms by the irreversible coagulation and denaturation of enzymes and structural proteins
• Dry heat sterilization methods

  • Hot air oven sterilizer
  • Flaming
  • High vacuum Infra red sterilizer
• Steam sterilization - Autoclave


  The oldest and most recognized agent for inactivation of microorganisms, achieves rapid heating and penetration, no toxicity to workers, inexpensive, can damage delicate instruments
• Types of autoclaves


  • Common Laboratory Autoclave
  • Pressure Cooker Type
  • Vertical Autoclave
  • Large Automatic Hospital Autoclave
  • Horizontal Autoclave
• D-values

  Time to reduce the surviving population by 99%, at a particular temperature, allows direct comparison of the heat resistance of microorganisms
• D121c-Values for Bacillus stearothermophilus used to monitor the steam sterilization process
• Common mistakes in use of autoclaves/hot air ovens

  • Overloading of sterilizer chamber
  • Lack of separation between packs or trays
  • Incorrect packaging material
  • Excessive layering of wrap inhibiting penetration
  • Closed container not penetrated by steam
  • Dry heat sterilizer door opened to add more items without starting
  • Sterilizer timer malfunction
• Rapid Cycle or Flash Sterilization


  Unwrapped steam sterilization, originally defined by Underwood and Perkins as sterilization of an unwrapped object at 132°C for 3 minutes at 27-28 lbs. of pressure
• Monitoring Sterilization


  • Mechanical Indicators
  • Chemical Indicators
  • Biological Indicators
• Suggested protocol for management of positive biological indicator in a steam sterilizer

  1. Take the sterilizer out of service

  2. Notify area supervisor and infection control department

  3. Supplies processed since the last acceptable (negative) biological indicator should be recalled

  4. Repeat biological indicator test in three consecutive sterilizer cycles

  5. Check to ensure the sterilizer was used correctly

  6. Check with hospital maintenance for irregularities or changes in the hospital steam supply

  7. Close sterilizer down until the manufacturer can assure that it is operating properly

  8. Retest at that time with biological indicators in three consecutive sterilizer cycles
• Sterilization by Gaseous Processes

  • Ethylene oxide
  • Hydrogen peroxide
  • Peracetic acid
  • Glutaraldehyde
  • Formaldehyde
• Ethylene Oxide


  Highly penetrative, non-corrosive microbiocidal gas, useful for sterilization of heat-sensitive materials, alkylates protein, DNA, and RNA, disadvantages include lengthy cycle time, cost, and potential hazards to patients and staff
• Hydrogen Peroxide Gas


  Inactivates microorganisms primarily by the combined use of hydrogen peroxide gas and the generation of free radicals during the plasma phase of the cycle, can sterilize devices that cannot tolerate high temperatures and humidity
• Peracetic Acid Sterilization


  A highly biocidal oxidizer that maintains its efficacy in the presence of organic soil, can remove surface contaminants and denatures proteins and disrupts cell wall permeability
• Formaldehyde/Glutaraldehyde


  Give an effective sporicidal process, can be used to sterilize respiratory therapy equipment
• Sterilization by Ionizing Irradiation


  Includes X-rays, gamma rays, accelerated electrons, UV light and X-rays kill microorganisms by damaging DNA, used to sterilize large amounts of prepackaged single use items
• Sterilization by Filtration


  Membrane filters like the millipore filter made of nitrocellulose with a pore size of 0.22um, useful in sterilizing fluids such as antibiotic solutions, blood products
• Characteristics of an ideal sterilization process

  • High efficacy
  • Rapid activity
  • Strong penetrability
  • Material compatibility
  • Nontoxic
  • Organic material resistance
  • Adaptability
  • Monitoring capability
  • Cost effectiveness
• Advantages and disadvantages of sterilization methods

  • Peracetic Acid/Hydrogen Peroxide
  • Glutaraldehyde
  • Hydrogen Peroxide
  • Ortho-phthalaldehyde
  • Peracetic Acid
• Slow sporicidal activity


  Peracetic Acid
• Peracetic Acid


  • Rapid sterilization cycle time (30-45 minutes)
  • Low temperature (50-55°C) liquid immersion sterilization
  • Environmental friendly by-products (acetic acid, O2, H₂O)
  • Fully automated
  • Single-use system eliminates need for concentration testing
  • Standardized cycle
  • May enhance removal of organic material and endotoxin
  • No adverse health effects to operators under normal operating conditions
  • Compatible with many materials and instruments
  • Does not coagulate blood or fix tissues to surfaces
  • Sterilant flows through scope facilitating salt, protein, and microbe removal
  • Rapidly sporicidal
  • Provides procedure standardization (constant dilution, perfusion of channel, temperatures, exposure)
• Storage of Sterile Items

  • Protect sterility until ready to use
  • Store to protect packages from dust, moisture, falling on floor
  • Transport only covered, dry packages
  • Handle to protect package integrity
  • Rotate sterile items first in, first out
  • Store and label (date/time) for effective recall system
• Disinfectant use- considerations


  • Follow manufacturer's recommendations to avoid medical device damage
  • Use correct dilution – more is not better!
  • Use correct contact time
  • Use correct temperature
  • Understand environmental safety issues
  • Do not exceed exposure limits /Know permissible exposure levels
  • Assess compatibility with gloves, basins, other products