STERILISATION AND DISINFECTION Universities Press India Private Limited

STERILISATION AND DISINFECTION © Universities Press (India) Private Limited Universities Press

STERILISATION Sterilisation A process by which an article, surface or medium is free of all living organisms either in vegetative state or spore state Disinfection Removal or destruction of all pathogenic organisms Asepsis Prevention of infection by inhibiting the growth of bacteria © Universities Press (India) Private Limited Universities Press

STERILISATION Cleaning l Removal of soil and dirt to reduce microbial burden and to make sterilisation more effective Decontamination l The process of rendering an article or an area free of contamination including microbial, chemical, radioactive, etc. Bactericidal agents: Agents that kill bacteria Bacteriostatic agents: Agents that prevent multiplication of bacteria © Universities Press (India) Private Limited Universities Press

STERILISATION Objective: To destroy microorganisms from materials and areas Choice of method depends on: Purpose for which it is carried out, nature of microorganisms, material to be sterilised Uses of sterilisation: To prevent contamination by extraneous organisms, to prevent sepsis in surgery, for safety in food and drugs © Universities Press (India) Private Limited Universities Press

CLASSIFICATION Physical methods Sunlight, drying, dry heat - flaming - incineration, hot air oven Moist heat - Pasteurisation, boiling - Steam under normal pressure - Steam under pressure Filters, radiation Ultrasonic and sonic vibration © Universities Press (India) Private Limited Universities Press

CLASSIFICATION Chemical methods Alcohols - Ethyl alcohol, isopropyl alcohol Aldehydes - Formaldehyde, glutaraldehyde Dyes Halogens Phenols Surface active agents Metallic salts Gases: ETO, formaldehyde, betapropiolactone © Universities Press (India) Private Limited Universities Press

DRY HEAT © Universities Press (India) Private Limited Universities Press

FLAMING • Flaming: Inoculating loops, wires, tip of forceps, edges of test tubes © Universities Press (India) Private Limited Universities Press

HOT AIR OVEN Holding period – 160°C for 1 hour - Glassware, instruments, liquid paraffin, dusting powder, fats, grease, etc. - Rubber, cotton avoided Controls - C. tetani spores and Browne’s tubes © Universities Press (India) Private Limited Universities Press

HOT AIR OVEN Hot air oven © Universities Press (India) Private Limited Universities Press

INCINERATION Contaminated cloth, animal carcasses, pathological materials, infectious hospital waste © Universities Press (India) Private Limited Universities Press

STERILISATION CONTROL Physical l Temperature monitoring and thermocouples Chemical l Browne’s tube (green spot) Biological l Non-toxigenic strain of Clostridium tetani or Bacillus subtilis 6 l Paper strips impregnated with 10 spores inserted in pack to be sterilised © Universities Press (India) Private Limited Universities Press

MOIST HEAT Temp <100°C l Pasteurisation – Holder method- 63°C – 30 min – Flash method – 72°C – 20 sec Followed by quickly cooling to 13°C l Vaccine bath: Heat inactivation – 60°C – 1 hr l Inspissation: 80– 85°C 30 min on 3 days © Universities Press (India) Private Limited Universities Press

MOIST HEAT Temperature at 100°C l l Boiling Koch & Arnold steam steriliser: media – 90 min l Tyndalisation: sugars, gelatin l 100°C – 20 min - 3 successive days © Universities Press (India) Private Limited Universities Press

STEAMER Steamer © Universities Press (India) Private Limited Universities Press

MOIST HEAT l Temp >100°C : (Steam under pressure) Autoclaves A simple autoclave; 1. release valve; 2. safety valve; 3. pressure gauge; 4. tightening screws; 5. cover; 6. body; 7. bin containing material; 8. heating element; 9. stand © Universities Press (India) Private Limited Universities Press

STERILISATION CONTROL Physical l Temperature and pressure monitoring gauges, thermocouples Chemical l Bowie–Dick tapes l Biological l Bacillus stearothermophilus 106 spores © Universities Press (India) Private Limited Universities Press

FILTRATION - Heat labile fluids - sera, antibiotics, enzymes, toxins - Separation of virus from bacteria Types of filters: Candle filters Berkfeld & Mandler: Made of kieselghur, graded porosity, sterilised by steaming or autoclave Chamberland or Doulton: Made of unglazed ceramic © Universities Press (India) Private Limited Universities Press

FILTERS l Asbestos filters: Seitz filter: - pad of asbestos - inserted into metal holder - discarded after use Asbestos filter © Universities Press (India) Private Limited Universities Press

FILTERS l Sintered glass filters: Used for air filtration, made of finely ground glass Glass filter © Universities Press (India) Private Limited Universities Press

FILTERS Membrane filters: Cellulose nitrate - Also called gradacol MEM - To separate viruses, to know their size Cellulose acetate or millipore filters or oxoid MEM filters HEPA: High efficacy particulate air filters Membrane filter © Universities Press (India) Private Limited Universities Press

RADIATION Non-ionising radiation - Infrared and ultraviolet rays - low energy type - Control of closed environment with UV lamp - Bacteriological laboratory, inoculation hoods, laminar flow © Universities Press (India) Private Limited Universities Press

RADIATION Ionising radiation - Gamma rays, X rays and cosmic rays lethal to penetrative power No appreciable increase in temperature – ‘cold sterilisation’ Use: Sterilising pharmaceuticals, medical, dental equipment, sterilising plastics, syringes, swabs, catheters, oil grease © Universities Press (India) Private Limited Universities Press

CHEMICAL METHODS © Universities Press (India) Private Limited Universities Press

CHEMICAL METHODS Alcohols l Protein denaturation and lipid dissolution l Bactericidal, fungicidal l Not effective on spores and viruses l l Commonly used - Ethyl alcohol, isopropyl alcohol Concentration 60 -90% in water © Universities Press (India) Private Limited Universities Press

CHEMICAL METHODS Aldehydes Active against amino group in protein molecule Formaldehyde Used for sterilising instruments, heat-sensitive catheters, fumigation of wards, sick rooms and laboratories Glutaraldehyde l Disinfection of medical equipment like cystoscopes and bronchoscope l Effective against tubercle bacilli, fungi and viruses © Universities Press (India) Private Limited Universities Press

DYES Aniline dyes l Brilliant green, malachite green and crystal violet l Non-toxic, non-irritant l Active against Gram-positive organisms l Used as selective agents in culture media Acridine dyes l Proflavine, acriflavine and euflavine l Impair DNA, destroy the reproductive capacity of the cell © Universities Press (India) Private Limited Universities Press

CHEMICAL METHODS Phenols l Lister - antiseptic surgery l Distillation of tar between 170°C and 270°C l Damage to cell membrane, release cell contents and cell lysis l Cresols, chlorhexidine, hexachloraphane l Disinfection of floors, excreta, preoperative disinfection of skin © Universities Press (India) Private Limited Universities Press

CHEMICAL METHODS Halogens Iodine – Skin disinfectant l Bactericidal, sporicidal l Iodophores more active Chlorine – Used as hypochlorite l l Bactericidal Disinfect water supplies, swimming pools and used in diary industries © Universities Press (India) Private Limited Universities Press

GASES Ethylene oxide - Kills microorganisms by altering their DNA by alkylation of amino carboxyl, hydroxyl and sulphydryl groups in protein molecules - Used in sterilising packaged heat-sensitive devices - Respirators, heart–lung machines, dental equipment, sutures, books and clothing © Universities Press (India) Private Limited Universities Press

GASES Formaldehyde l Fumigation of theatres and rooms l 150 g of KMn. O 4 to 280 ml formalin for every 1000 cu ft. l Doors sealed, opened after 48 hrs Betapropiolactone (BPL) l Condensation product of ketane and formaldehyde l Hydrogen peroxide fogging l Short cycle time, non-toxic © Universities Press (India) Private Limited Universities Press

SURFACE ACTIVE AGENTS l Act by altering energy relationship at interfaces - reduction in surface tension Classification l Anionic, cationic, amphoteric, non-ionic l Antibacterial, fungicidal, virucidal l Cetavlon, cetrimide © Universities Press (India) Private Limited Universities Press

SALTS OF HEAVY METALS l l l Copper, silver, mercury Combine with sulphydryl groups of cell enzymes, denaturation of enzymes Highly toxic Thiomersal, mercurochrome less toxic, used as mild antiseptics Copper salts - fungicide © Universities Press (India) Private Limited Universities Press

PLASMA l l l Produced at very high temperature or low temperature in strong electromagnetic fields Plasma consists of ions, electrons and free radicals Used for arthroscopes, urethroscopes © Universities Press (India) Private Limited Universities Press

DISINFECTION Spaulding Classification l Eagle H Spaulding believed that the method used to disinfect an object will depend on the object’s intended use © Universities Press (India) Private Limited Universities Press

WHICH PROCEDURE TO USE? Category Items in each category Procedure Critical Items that: (1) enter the tissue; (2) Enter vascular system; (3) through which blood flows High level disinfection Semi-critical Items that: (1) touch mucous membranes; (2) touch non-intact skin (e. g. endoscopes, respiratory therapy equipment, thermometer) Intermediate level disinfection Non-critical Items such as bedpans, blood pressure cuffs, and bedside tables Low level disinfection © Universities Press (India) Private Limited Universities Press