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Disinfectants and Antiseptics

• Disinfectants and antiseptics differ from systemically active antimicrobials because they have little selective toxicity.
• They are toxic to both microbial pathogens and host cells.
• Disinfectants and antiseptics are used to inactivate microorganisms in the inanimate environment and, to a limited extent, on skin surfaces.
• They cannot be administered systemically.

Sterilization

• Sterilization is the process of freeing an article, surface, or medium of all microorganisms, whether pathogenic or nonpathogenic, in their vegetative or spore state.
• Sterilization methods: physical and chemical.
• Sterilization results in a reduction of ≥10^6 log CFU (colony-forming units) of microorganisms and their spores.

Antiseptics

• Antiseptics come from the Greek words αντι (anti, against) and σηπτικος (septikos, putrefactive).
• They are antimicrobial substances applied to living tissue or skin.
• They reduce the possibility of infection, sepsis, or putrefaction.
• Antiseptics should be distinguished from antibiotics and disinfectants.
• Antibiotics destroy microorganisms within the body.
• Disinfectants destroy microorganisms found on non-living objects.
• Germicides, are able to destroy microbes (bacteriocidal).
• Other antiseptics are bacteriostatic, which only prevent or inhibit their growth. -Antibacterial antiseptics only affect bacteria.
• Common antiseptics include alcohols, quaternary ammonium compounds, boric acid, chlorhexidine gluconate, hydrogen peroxide, iodine, mercurochrome, octenidine dihydrochloride, phenol compounds, sodium chloride, and sodium hypochlorite.

Disinfectants

• Disinfectants are antimicrobial agents used to destroy microorganisms on non-living objects.
• This process of destroying microorganisms on non-living objects is called disinfection.
• Disinfectants should be distinguished from antibiotics and antiseptics.
• Sanitisers are high-level disinfectants that kill over 99.9% of a target microorganism.
• Very few disinfectants and sanitisers can sterilise (the complete elimination of all microorganisms).
• Effectiveness depends on their mode of application.
• Bacterial endospores are most resistant to disinfectants.
• Viruses and bacteria also possess some tolerance.
• Types of disinfectants include alcohols, aldehydes, halogens, oxidizing agents, quaternary ammonium compounds, and others.

Categories of Disinfectants

• High-Level Disinfectants (HLD): Capable of killing all microorganisms and bacterial spores when used in sufficient concentration under suitable conditions.
• Intermediate-Level Disinfectants (ILD): Destroy all microorganisms but not bacterial spores.
• Low-Level Disinfectants (LLD): Destroy vegetative bacteria and enveloped viruses.
• LLD have variable action on non-enveloped viruses and fungi.
• LLD have no action on tubercle bacilli and spores.
• Antiseptics: Disinfectants that can safely be used on living tissues (used for asepsis).

Sanitization

• Sanitization is disinfection used in connection with food & catering equipment.

Decontamination or Cleaning

• Decontamination or cleaning is the process by which an area or article is rendered free of contamination (microbial, chemical, or radioactive) to a level at which items are considered safe without protective attire.
• Sanitization results in a reduction of at least ≥1 log CFU of most microorganisms but not spores.

Physical Agents

• Physical agents for disinfection and sterilisation include sunlight, drying, heat, filtration, radiation, and ultrasonic & sonic vibration.

Sunlight

• Ultraviolet (UV) rays of sunlight have bactericidal activity leading to spontaneous natural sterilization.
• UV rays are filtered by the ozone layer and impurities in the atmosphere.
• There occurs a more appreciable bactericidal effect in tropical countries where there is less impurity.

Drying

• Water constitutes 80% of body weight of bacteria and drying therefore has deleterious effect on bacterial growth, however bacterial spores are unaffected.

Heat

• Heat is the most reliable method of sterilization, and method of choice unless it is contraindicated.
• Dry heat: kills by protein denaturation, oxidative damage, and toxic effect of elevated electrolytes.
• Moist heat: kills by protein denaturation & coagulation.

Dry Heat Methods

• Red Heat: Inoculating loops, wires, tips of forceps, and scissors are held vertically in flame until red hot.
• Flaming: Scalpel blades, glass slides, mouth of culture tubes, and bottles are exposed to flame briefly without heating them to become visibly red.
• Incineration: Efficient for destroying contaminated materials like soiled dressings, animal carcasses, and pathological materials.
• Disadvantage: Cannot incinerate polystyrene materials because they emit clouds of dense toxic smoke.
• Plastics like polyvinyl chloride and polythene can be incinerated.

Hot Air Oven

• Most widely used method of dry heat sterilization for sterilizing loads damaged by moist heat.
• Hot air ovens tolerate high temperature (160 °C-180 °C).
• Acts by oxidation of cell constituents.
• Used to sterilize glassware, forceps, scissors, scalpels and others.
• Operation: heated electrically with heating elements in the walls of the chamber.
• A fan is fitted inside for even distribution of air.
• Has a temperature indicator, control thermostat, timer, open mesh shelving, and wall insulation.
• Sterilization temperature ensures sterilization hold starts only when required temp is reached as detected by thermocouples.
• Materials to be sterilized are cleaned, dried, and packed loosely.
• This allows optimum heat transfer.
• Glass test tubes with slip-on aluminum caps are placed vertically in metal racks.
• Ends of pipettes are stoppered 2cm deep with non-absorbent cotton wool and kept in metal canisters.
• Powders, fats, oils, and greases are sterilized in sealed metal containers.
• Temperature-time cycles: 160°C for 120 minutes, 170°C for 60 minutes, 150°C for 150 minutes.
• Cooling: The oven is cooled for 2 hours before the door is opened.
• Sterilization controls is the use of bacillus atrophaeus.
• Efficacy test with nontoxigenic strains of clostridium tetani..
• Browne's tube: Containing red colour solution turns green, indicates proper sterilization.

Moist Heat

• Temperature Below 100°C.

Pasteurization

• Used to control microorganisms in beverages.
• Holder method: Heated at 63°C for 30 minutes.
• Flash method: Heated at 72°C for 20 seconds.
• Then rapidly cooled to 13°C.
• UHT Sterilisation: Milk & milk products are heated at 140-150°C for 1-3 seconds.

Water Bath

• Water bath vaccines or serum containing coagulable protein is kept in a water bath at 60°C for 1 hour, for example, Typhoid vaccine.

Inspissation

• Inspissation (fractional sterilization)- media like Lowenstein Jensen's medium is heated at 80-85°C for 30 minutes, repeated for 3 days with a special instrument (Inspissator).

Temp at 100°C

• Boiling: vegetative bacteria almost die immediately-spores requires a longer time (20-30 mins), not ideal for surgical instruments.
• Steam at atmospheric pressure: (Koch's/ Arnold steam sterilization), a single exposure (90 mins) ensures sterilization.
• Tyndallisation: exposure to steam at 100°C, sugar & gelatin media, 20 min for 3 successive days to kill spores.

Temp above 100°C

• Autoclave:
• Water boils when its vapour pressure equals the surrounding atmosphere.
• Pressure: a closed vessel rises, water boils at a higher temperature and releases steam.
• Steam: good penetrating power and condenses, latent heat to the article.
• Creates a vacuum, drawing more steam and raises the steam temperature
• Vertical or horizontal cylinder: A steam jacket (water compartment).
• Gunmetal or stainless steel material.
• Lid is airtight with screw clamps and asbestos washer.
• Upper side: discharge tap, pressure gauge, safety valve.
• Heating is done electrically.

Autoclave Use

• All critical and semi-critical items that are both heat and moisture resistant.
• Surgical instruments, anesthetic equipment, dental instruments, and implanted medical devices.
• Used for surgical drapes and linens.
• Can sterilize for sterilization of various culture media & aqueous solutions, surgical dressings, pharmaceutical products and biohazardous wastes.
• Autoclavable plastic containers.

Autoclave Method of Operation

• Water is adjusted, articles are placed on perforated tray, lid is closed & autoclave is switched on.
• Conditioning phase: Safety valve is adjusted, discharge tap is closed.
• When desired pressure is reached (15 lbs psi), the safety valve opens & excess steam escapes.
• From this point holding time is calculated (15 mins).
• Exhaust phase: switched off to cool till pressure inside is equal atmospheric pressure and discharge tap is opened.

Autoclave Precautions

• Tap should not be opened if pressure is high, violent.
• If it is opened after the inside pressure has fallen below atmospheric, excessive water evaporates.
• Sterilization conditions - a temperature of 121°C for 15 minutes, 126°C for 10 minutes, or 134°C for 3 minutes.
• Sterilization controls are used for sterilization conditions.

Sterilization Controls for Autoclave Use

• Geobacillus stearothermophilus (thermophile) is used to test efficacy by moist heat.
• Spores grow at 55- 60°C & require an exposure of 12 mins at 121°C to be killed.
• Paper strips (106 spores), parts of the load.
• After, inoculated & incubated at 55°C for 5 days.
• Changes colour from purple to yellow results indicate improper.
• Autoclave tape indicates a heat sensitive material that undergoes colour change to indicate parameters are achieved.

Filtration

• Filtration sterilizes heat sensitive liquids like serum, sugars & antibiotic solutions.
• Only bacteria is removed through this process.

Depth Filters

• Depth filters are porous and filter particles: metallic, polymeric or inorganic material.
• Depth filters are rated by density & thickness of filters.
• Examples: candle filters, unglazed porcelain, asbestos filters and sintered glass filters.
• Uses are in industrial applications, food, beverages & chemicals.
• Depth filters can retain a mass of particles, fluids are high, and low cost.
• Particles still go through- filtration is bacteria filled.

Membrane Filters

• Membrane filters are manufactured of cellulose nitrate, polyvinylidene chloride.
• Sterilizes solutions- parenteral use.
• 0.22 µm pore size.

Air Filters

• Air filters are made of surgical masks and HEPA filters.
• Surgical masks: (3 ply mask): polypropylene between non woven fabric.
• The large air volumes free agents: high (HEPA) filters at 99.97% (0.3µ ).
• Used in Biosafety, used in OTs.
• Ultra low particulate filters removes dust, pollen, mold, bacteria and air.
• The ultra low particles are 0.12µm or higher.
• Filtration removes water: bacteria pharmaceutical fluids.

Filtration Sterilization Control

• Brevundimonas diminuta
• Serratia marsecens

Radiation

• Non ionizing radiation affects DNA (glass, thin films).
• Infrared rapid.
• mass sterilization pre-items.
• Ultraviolet enclosed cabinets where germs are handled/water and drinking use.
• The 250-300nm wavelength ray should take about half an hour.
• Gamma rays from cobalt, high heat and increased DNA levels
• Used for transplant tissues- gloves and oils that are unable tolerate heat.
• Spoilage control is bacillus pumilus.

Incineration

• Incineration occurs to treat wastes.
• Occurs 870- 1,200°C, a high temperature.

Microwave

• Microwaves disinfect lenses and urinate catheters (2450 MHz);
• MOA: generates heat through friction.

Chemical Disinfectants

• Microorganisms are killed in a chemical.
• Different cells vary- gram/myco resist slow high.
• Chemicals include phenolics hypochlorites compounds.

High-Level Disinfectants (HLD)

• Kill spores, sufficient concentrations.

Aldehyde (HLD)

• Formaldehyde, ortho molecules.
• Inactive through linking.

Ortho-phthalaldehyde (OPA)

• Semicritical in 60% items (5-10 min).
• Better smell faster.

Disadvantages:

• kills stains.

Formaldehyde

• Preservative for specimen
• Embalming Agent uses:
• It remains an active matter. A pungent smell, a skin hazard.

Peracetic Acid:

• 0.1-0.2 molecules (5-15).
• For instruments-damage eye.
• hydroxyl-component attacker.

Hydrogen Peroxide:

• 3-6% to disinfect contact lens
• Advantages- detergent organic.
• Disadvantages: irritation to eyes, chemical concerns of patients.

Potassium Permanganate

• Disenfects aquariums and pulls bacteria before teeth are removed

Intermediate-Level Disinfectants

Alcohol

• Spores prevent 60-80.
• Alcohol sterilize small instruments/material
• small medical items.
• Skin antiseptic.
• Disadvantages: matters/damage.

Phenolics

• Joseph Lister antiseptic ( father antiseptic.
• Lysol environmental surfaces/medical sterilization
• Myco bactericidal 5%.
• Anti Chloroxylenol.
• Retain activity in matters causes.

Halogens (carbolic)

• Disrupt wall and cause toxic reaction.

Tincture of iodine

• Tincture of iodine is the disinfectant: It 2 and cause staining.
• With carrier iodine prepares release.
• 7 point 5/ 10 preparations.

Dichloride

• Form tables chlorine.
• Bacteria infection

Sterilization of heat

• Is disinfection of equipment.

Radiation

• Non ionization materials on the UV radiation and are less safe

Steaming Radiation

• An egg based culture with sterilization

QAC: Compound Action

• Protein disrupt.
• An environmental noncritical.

Biguanide

• Disrupt membrane
• Wash solution to kill
• Action pH can great presence
• Disinfect surgical.

Infection Cleaning

• Enzyme cleaners' proteolytic.
• Cleaning action detergent.
• Manual by cloth.
• Instrument machine is useful.
• Use cleaning.