INTRODUCTION: Sterilization : the process by which an article, surface or medium is freed of all living micro-organisms either in the vegetative or spore state. Disinfection : destruction or removal of all pathogenic organisms or organisms capable of giving rise to infection Anti-sepsis : prevention of infection usually by inhibiting the growth of bacteria in wounds or tissues
HISTORY OF ASEPSIS Zaccharias Jansenin 1590 and Robert Hookein 1660 opened the world of microbes to mankind by their inventions of microscopes Anton Van Leeuwenhoek :a tradesman and scientist from Netherlands……… “Animolecules” in 1667 through his handcrafted microscope. Microbes became visible when he observed tooth scrapings and gutter water under a simple microscope. Semmelweis (1847) – washing hands prior to delivery reduced puerperal fever Lister (1865) –suggested carbolic acid as an antiseptic Pasteur and John Tyndallused boiling water to kill bacteria and the process was known as Pasteurization Ernst von Bergmann (1880) – introduced autoclave Further acceleration in the field of sterilization, disinfection and infection control progressed when finally in 1890’s the advent of Steam sterilizers, Sterile gowns, drapes and Gloves emerged.
CLASSIFICATION PHYSICAL AGENTS: 1) SUNLIGHT 2) DRYING 3) DRY HEAT a) Flaming b) Incineration c) Hot Air 4) MOIST HEAT: Pasteurisation, Boiling, Steam Under Normal Pressure, Steam Under Pressure. 5) FILTRATION: Candles, Asbestos Membranes. 6) RADIATION 7) ULTRASONIC AND SONIC VIBRATIONS CHEMICAL AGENTS: 1) ALCOHOLS 2) ALDEHYDES 3) DYES 4)HALOGENS 5) PHENOLS 6) SURFACE ACTIVE AGENTS 7) METALIC SALTS 8) GASES
IDEAL PROPERTIES An ideal antiseptic or disinfectant should: • Have a wide spectrum of activity and be effective against all micro organisms • Be active in the presence of organic matter • Be effective in acid as well as alkaline media • Have speedy action • High penetrating power • Be stable • Be compatible with other antiseptics and disinfectants • Not corrode metals, not cause local irritation or sensitization • Not interfere with healing • Non toxic if absorbed into circulation • To be cheap and easily available • Be safe and easy to use
FACTORS THAT DETERMINE THE POTENCY OF DISINFECTANTS • Concentration of the substance • Time of action • pH of the medium • Temperature • Nature of the organism • Presence of extraneous material
MODES OF ACTION • Protein coagulation • Disruption of cell membrane • Removal of the free sulphydryl groups • Substrate competition
Physical AgentsSUNLIGHT • Bactericidal activity • Under natural conditions Action: primarily- UV rays DRYING • 4/5th by wt bacterial cell-water • Drying-deleterious effect on bacteria • Unreliable &theoretical interest • spores are not effected
HEAT • Most reliable method • Factors influencing: a. Nature of heat b. Temperature & time c. Number of microorganisms present d. Characteristic of organisms e. Type of material
I. Dry heat (principle:denaturationof protien) 1) Flaming: tips of the instrument held in the bunsen flame till red hot. • Indications: loops/ innoculating wires/forcep points/ scalpels/needles. • Disadvantage: • Not completely sporicidal. • Restricts the number and size of instruments.
2. Incineration: Destruction of materials – • Soiled dressings • Animal carcasses • Bedding • Pathological materials • Plastics-PVC, polythene • Except polystyrene.
3. Hot Air Oven: • Pastuer-1876 • Holding period-160c-1hr • Sterilizes-glassware, forceps, scissors, scalpels, all-glass syringes, swabs, liquid paraffin, • Disadv: .dry heat- bad conductor • poor penetration • spore resistance • Control: Clostridium tetani
MOIST HEAT • Temperature <100c • Pasteurization of milk: holder method -63c-1/2hr flash method -72c-15-20 sec Cooling quickly -13c or lower
Temperature at 100c: Boiling: • vegetative bacteria-90-100c • hard water-not to be used • 2%NaHCO3-increases boiling point of water.
Steam at atmospheric pressure 100c • Also known ascompressed or saturated steam • This is an inexpensive method using aKoch orArnold steamer. • Principle • steam under pressure ishotter • higher the pressure the higher the temperature • Liquids were sterilized by this method at1000C for 30minon each of3 successive days. • Also calledFractional sterilization, because a fraction was accomplished on each day. • Also calledTyndallizationafter its developerJohn Tyndall, and Intermittent sterilizationbecause it has a stop and start operation.
Tyndallisation or Intermittent sterilization… • During thefirst day’sexposure, steam kills virtually all organismsexcept bacterial sporesand itstimulatesspores to germinate into vegetative cells. • During overnight incubationthe cells multiply and arekilled on second day. • Again the material is cooled and afew remaining sporesgerminate only to be killed on the3rd day. “This method also fails because thermophils andcertain spores ( eg., some anaerobes ) fail to germinate. A suitable medium for germination such as broth is required”.
AUTOCLAVE STEAM UNDER PRESSURE: * Principle: water boils when its vapour pressure equals that of the surrounding atmosphere. * Saturated steam has penetrative power. when steam comes in to contact with a cooler surface it condenses to water and gives up its latent heat to that surface . *Reduction in volume sucks in more steam to the area and the process continues till temperature of surface = steam. The condensed water ensures moist conditions for killing the microbes present. *Temperature: between 108 ° C and 147 °C (121 °C) * Pressure: 15psi * Duration: 15 mins * Items: Dressings , instruments, gloves, laboratory ware, media and pharmaceutical products
PRINCIPLE….. Dry saturated steam Meets cooler surface Gets condensed into water Denat. of proteins Latent heat lib. Membrane dmg 16OO ml steam at 100 oC Leakage of cellular cont. & at atmospheric pressure condenses Chromosomal dmg into 1ml H2O → 518 cal heat Enzyme coagulation.
As the water molecules in steam becomemore energized, their penetration also increases • Same principle is used in homepressure cooker. • It is important to note that sterilizing agent ismoist heatbut not the pressure.
Recommended Cycles Settings for general wrapped items: • Temp. - 121 degree C Pressure - 20 PSI • Time -- 30 min Setting Settings for bottled solutions: • Always vent bottles to avoid bursting! • Temp. - 121 degree C Pressure - 20 PSI • Time -- 30 min Setting Setting for "Flashing" an unwrapped instrument: • Temp. – 132 degree C Pressure - 30 PSI • Time -- 4-7 Min Setting
This method can be used for a broad variety of items such as instruments, clothing, glassware, cotton etc. • Limitations : • Plastic ware melts in high heat • Sharp instruments become dull and corrode • Many chemicals breakdown during the sterilization process, and oily substances cannot be treated since they do not mix with water.
Several types of steam sterilizers are in use: • Laboratory autoclaves • Hospital dressing sterilizers • Bowland instrument sterilizers, and • Rapid cooling sterilizers (even the domestic pressure can be used as a sterilizer).
Pre-vacuum Autoclave • A new form of autoclave called thePrevacuum autoclavehas been developed, whichdraws air outof the chamber at the beginning of the cycle. The major advantage of this isminimal exposure. • In the absence of air, steam is able to penetrate toall instrument surfaces, including inside the narrow lumens of hollow instruments such as dental handpiecesand scopes.
Unsaturated Chemical Vapour Sterilization • This system depends on heat, water and chemical combination for it’s efficacy • The temperature and pressure required is greaterthan that for autoclave • It is known as aChemiclave • Instead of distilled water a solution ofalcohol, formaldehyde, ketone, acetone and wateris used to produce the sterilizing vapor • Temperature : 1310C at 20 pounds pressure for 20 to 40 minutes
STERILISATION CONTROL * For determining the efficacy of moist heat sterlisation , spores of bacillus stearothermophilus are used as the test organism. Chemical indicators , autoclave tapes and thermocouples may also be used instead.
FILTRATION To remove bacteria from heat labile liquids -sera, sugar solutions & antibiotics. Types: a. candle filters: i. Unglazed ceramic filters ii. Diatomaceous earth filters b. Asbestos filters: c. Sintered glass filters d. Membrane filters
Ionizing X ray, gamma, beta rays. Use: plastics,cultureplates,catheters,tubes, swabs Adv: large scale use. Disadv:sporicidial effect ? Non ionizing Infra red, UV radiation Use:syringes, catheters (IR) entry ways/OTs/lab (UV) Disadv: longer wavelength hence poor penetration Radiation
I. Phenols 1.Carbolic acid/phenol: • Mech of action:* membrane damage. * protein precipitation * protoplasmic poison. Disadv:* highly caustic * poor sporicidial.
2.Hexachlorophene: Uses: .skin disinfectant .Presurgical showers for patients/surgeons. .prophylaxis against staphylococcal infection in nurseries. Advantage: stays on the skin surface for longer time disadvantage: absorption by skin barrier in neonates at high concentrations
3.CHLOROXYLENOL • Non corrosive, non irritant • 4.8 % + 9 % terpinol + 13 % alcohol DETTOL 4.CRESOL • 3-10 times more active than carbolic acid • 50% soapy emulsion LYSOL
II.ALCOHOLS:(mech of action: denaturation of bacterial protiens) • Ethanol • Isopropyl alcohol 70%-90% conc volatile • Methyl alcohol used for quick drying thermometers/trolley tops on physically clean cabinets/incubators surfaces. Disadvantage : . inflammable caution during diathermy . Mucus membrane irritant. . Organic enviornment slows action. . Promotes rusting.
III. Aldehydes(active against amino group in protien molecule) 1.Formaldehyde: bactericidial/sporicidial(?)/viricidial. • Liquid form: formalin(37% soln) 10% formalin + 0.5% Na tetraborate used for clean metal instrument….eg. Endoscope,dialysis equipment. • Vapour form: fumigation of wards/corridors/ICUs • Formaldehyde releasing agents:.noxythiolin(Rx peritonitis) . taurolin
2.Glutaraldehyde/Cidex(2% alkaline NaHCO3): • Prolonged action • Posseses high microbicidial activity against bacteria, spores, yeasts, fungi, tubercle bacilli and • Less toxic n irritant to the eyes & skin than formaldehyde • Exposure time: > 10hrs. catheters. common uses .heat labile instruments polythene tubes. . Bronchoscopes. endotracheal tube. . Endoscopes. . clean metal instruments. . Face masks.
IIIGases/vapour based disinfectants 1.Ethylene Oxide:ETO gas. (action: alkylation of Amino-hydroxyl-sulphydryl groups in bacterial protien) • Advantage: readily absorbed in water/organic solvents, rubber/plastics/oils. • Disadvantage: . inflammable in >3% conc(mix with CO2). . Mutagenecity/carcinogenic…toxic hazard.
2.Formaldehyde: procedure: • windows & outlets are sealed. • 150gms of KMnO4 added to 280ml formalin for every 1000cft. • Considerable heat & vapours generated. • Doors kept closed for 48hrs. 3.beta-Propiolactone / BPL( 0.2% ): • More efficient than formaldehyde….but more carcinogenic at the same time.
V. Biguanides: Chlorhexidine: • available as dihydrochloride,diacetate,gluconate. • wide range of activity against gm+/- organisms. • low activity against spores/viruses(Curd et al 1946). • More active in a alkaline pH and activity reduced in presence of soaps.
IV. Surface active agents 3 types: • anionic ordinary soaps. • cationic quats cetrimide&benzalkonium chloride. • non ionic uses: wetting agents/emulsifiers/detergents.
V. Dyes: a) aniline dyes and b) acridine dyes Used extensively as skin and wound antiseptics (bacteriostatics in high dilution but of low bactericidal activity). Gm+ve>>Gm –ve No activity against tubercle bacilli. Lethal effects on bacteria are due to their reactions with the acid groups in the cell.
VI. Halogens: 1) Iodine in aqueous and alcoholic solutions has been used as a SKIN DISINFECTANT. Active bactericidal agent with a moderate activity against spores, tubercle bacillus and number of viruses. Compunds of iodine ( iodophores) are more active than aqueous or alcoholic soln. 2) Chlorine and hypochlorites are markedly bactericidal. They have a wide spectrum of activity against viruses. * The organic chloramines are used as antiseptics for dressing wounds.
VII Metallic salts: Salts of silver, copper, and mercury are used as disinfectants. Protein coagulants and have the capactiy combine with free sulphydyrl groups of cell enzymes. Organic compounds, thiomersal, phenyl mercury nitrate and mercurochrome are less toxic and are used as mild antiseptics and marked bacteriostatics, limited fungicidal and weak bactericidal activity.
CLASSIFICATION OF INSTRUMENTS • CRITICAL - objects which enter normally sterile tissue or the vascular system or through which blood flows. Scalpels, scalers, surgical forceps, burs, explorers, chisels etc Steam (autoclave), dry heat, chemical strilization • SEMICRITICAL - objects that contact mucous membranes or non intact skin. Impression trays, amalgam condensors, anesthesia equipment Sterilization/high level disinfection • NONCRITICAL - come in contact with intact skin but not mucous membranes. Intact skin - barrier to most organisms. BP cuff, restorative materials, varnish, liners, bed pans etc Alcohols, phenols, iodophores, household bleach
UNIVERSAL PRECAUTIONS • CONCEPT: To address the inability of health care providers to specifically identify all patients with communicable diseases. THEORY: protection of self , staff and patients from contamination by using barrier techniques when treating all patients as if they all had a communicable disease ensures that everyone is protected from those who do have an infectious process. COMPONENTS: • All doctors and staff who come in contact with patients blood or secrtetions , whether directly or in aerosol form , wear barrier devices including face mask eye protection and gloves • decontaminating or disposing of all surfaces that are exposed to patient blood tissues and secretions . • avoidance of touching and thereby contaminating surfaces ( eg: dental record , telephone, etc.,) with contaminated gloves or instruments.
PERSONAL BARRIER PROTECTION GLOVES: • All clinical personnel must wear treatment gloves during all treatment procedures. • After each appointment , or if leak is detected , remove gloves, wash hands and put on fresh gloves. • Instead of attempting to wash gloved hands before opening drawers or handling items adjacent to the operatory, use tongs , a paper towel, or a food handler’s over glove, to prevent contamination. • All personnel with weeping or draining lesions that could infect patients abstain from patient contact.
Gloves that become penetrated or torn can imbibe patient fluids and therefore should be removed. • Viruses have been found to penetrate not more than one intact latex gloves out of hundred. Double gloving prevents perforations of the inner glove and therefore, adds protection. • Latex gloves must have less than four percent leak detectable water test. While handling sharp instrument wear puncture resistant utility gloves. • Nitrile latex gloves can be washed inside and out, disinfected or steam autoclaved
PROTECTIVE MASKS AND HAIR PROTECTION. • wear masks to protect against heavy spatter ,blood droplets. Change the mask between every patient or whenever it becomes visibly soiled or moist. • masks with highest filtration are rectangular, folded types used for surgeries. • hair can trap heavy contamination hence should be kept out of the treatment field by a protective head cap.