Antisepsis

• Disinfection


  The killing of many, but not all, microorganisms
• For adequate disinfection, pathogens must be killed, but some organisms and bacterial spores may survive
• Disinfectants


  • Vary in their tissue-damaging properties from corrosive phenol-containing compounds, which should be used only on inanimate objects, to less toxic materials such as ethanol and iodine, which can be used on skin surfaces

  
• Antiseptics


  Chemicals used to kill microorganisms on the surface of skin and mucous membranes
• Antiseptics


  • Lysol (pheno-derivative; not good for skin)
  • Ethanol, isopropyl alcohol (can be used for skin surfaces)
• Antiseptics vs Disinfectants

  Antiseptics are chemicals intended to reduce or destroy microorganisms on living tissue (eg., skin), as opposed to disinfectants, which are used on inanimate objects (e.g., medical devices such as endoscopes)
• Levels of Disinfection

  • High-level disinfection (HLD)
  • Intermediate-level disinfection
  • Low-level disinfection
• High-level disinfection (HLD)


  The destruction of all viruses, vegetative bacteria, fungi, mycobacterium, and some, but not all, bacterial spores
• Intermediate-level disinfection


  The destruction of all mycobacteria, vegetative bacteria, fungal spores, and some nonlipid viruses, but not bacterial spores
• Low-level disinfection


  A process that can kill most bacteria (except mycobacteria or bacterial spores), most viruses (except some nonlipid viruses), and some fungi
• Sterilization


  The killing or removal of all microorganisms, including bacterial spores, which are highly resistant
• Antibiotics

  Taken inside
• Sterilization


  Taken outside
• Sterilization by autoclaving

  Exposure to steam at 121oC under the pressure of 15 lb/in2 for 15 minutes
• Sterilization of surgical instruments that can be damaged by moist heat

  Exposure to ethylene oxide gas
• Ethylene oxide (EO)


  A low temperature gaseous process widely used to sterilize a variety of healthcare products, such as single-use medical devices
• Ethylene oxide


  • It is an alkylating agent that disrupts cellular metabolism and reproductive processes of microorganisms
  • It penetrates breathable packaging, making contact with all accessible surfaces of the product to deliver the required sterility assurance level (SAL)

  
• Products commonly processed with ethylene oxide

  • Assembled complex devices
  • Catheters
  • Custom procedure packs
  • Equipment with integrated electronics
  • Multi-lumen tubing products
  • Stents
  • Wound care dressings
• Sterilization of intravenous solutions

  By filtration
• Chemical agents


  • Vary greatly in their ability to kill microorganisms
  • Act primarily by one of three mechanisms: 1) Disruption of the lipid-containing cell membrane, 2) Modification of protein, 3) Modification of DNA
• Alcohol


  Ethanol is widely used to clean the skin before immunization or venipuncture. It acts mainly by disorganizing the lipid structure in membranes, but it denatures protein as well. Ethanol requires the presence of water for maximal activity; ie, it is far more effective at 70% than at 100%. Alcohol with water is more effective compared to alcohol alone.
• Detergents


  Are "surface-active" agents composed of long-chain, lipid soluble, hydrophobic portion and a polar hydrophilic group, which can be a cation, an anion, or a nonionic group. They interact with the lipid in the cell membrane through their hydrophobic chain and with the surrounding water through their polar group and thus disrupt the membrane.
• Phenol


  Was the first disinfectant in the operating room (by Lister in the 1860s), but it is rarely used as a disinfectant today because it is too caustic. Phenols not only damage membranes but also denatures proteins.
• Phenol derivatives


  • Hexachlorophene, a biphenol with six chlorine atoms, used in germicidal soaps
  • Cresol (methylphenol), the active ingredient in Lysol

  
• Chlorine


  A powerful oxidizing agent that kills by cross-linking essential sulfhydryl groups in enzyme that form the inactive disulfide. They destroy secondary and tertiary protein structures; thus, protein loses its shape.
• Iodine


  The most effective skin antiseptic used in medical practice and should be used prior to obtaining a blood culture and installing intravenous catheters because contamination with skin flora such as Staphylococcus epidermis can be a problem. Iodine, like chlorine, is an oxidant that inactivates sulfhydryl-containing enzyme. It also binds specifically to tyrosine in protein.

  
• Forms of iodine

  • Tincture of iodine (2% solution of iodine and potassium iodide in ethanol)
  • Iodophors (complexes of iodine detergent)
• Heavy metal salts


  Mercury and silver have the greatest antibacterial activity of the heavy metals and are the most widely used in medicine. They act by binding to sulfhydryl groups, thereby blocking enzymatic activity.
• Heavy metal antiseptics


  • Thimerosal and merbomin, which contains mercury, used as skin antiseptics
  • Silver nitrate drops useful in preventing gonococcal ophthalmia neonatorum
  • Silver sulfadiazine used to prevent infection of burn wounds

  
• Hydrogen peroxide


  Used as an antiseptic to clean wounds and to disinfect contact lenses. Its effectiveness is limited by the organism's ability to produce catalase enzyme that degrades H2O2. It is an oxidizing agent that attacks sulfhydryl groups, thereby inhibiting enzymatic activity.

  
• Formaldehyde

  Available as a 37% solution in water (Formalin), denatures protein and nucleic acids.

  
• Glutaraldehyde


  Also denatures protein and nucleic acids.
• Thimerosal


  Mercury-containing skin antiseptic
• Merbomin


  Mercury-containing skin antiseptic
• Antiseptics


  • Used to prevent infection of wounds and skin
• Silver nitrate drops


  Used to prevent gonococcal ophthalmia neonatorum

  
• Silver sulfadiazine


  Used to prevent infection of burn wounds

  
• Hydrogen peroxide


  Used as an antiseptic to clean wounds and disinfect contact lenses

  
• Hydrogen peroxide


  • Its effectiveness is limited by the organism's ability to produce catalase enzyme that degrades H2O2
  • The bubbles produced when peroxide is used on wounds are formed by oxygen arising from the breakdown of H2O2 by tissue catalase
• Mechanism of action of hydrogen peroxide

  Hydrogen peroxide is an oxidizing agent that attacks sulfhydryl groups, thereby inhibiting enzymatic activity