Sterlisation and disinfection

STERILISATION STERILISATION AND AND DISINFECTION DISINFECTION

DR.ASIF IQBALDR.ASIF IQBAL Date : 14-08-2014 Date : 14-08-2014

Objective of sterilization Objective of sterilization – –Removal of microorganisms or destroy them Removal of microorganisms or destroy them

from materials or from areas since they cause from materials or from areas since they cause contamination, infection and decay.contamination, infection and decay.

In microbiology - to prevent contamination In microbiology - to prevent contamination Surgery - to maintain asepsis Surgery - to maintain asepsis Drug & food -for ensuring the safety Drug & food -for ensuring the safety

Definitions Definitions SterilizationSterilization – T – The process by which an he process by which an

article, surface, or medium is freed of all living article, surface, or medium is freed of all living microorganisms either in the vegetative or microorganisms either in the vegetative or spore state spore state

DisinfectionDisinfection – The destruction or removal of – The destruction or removal of all pathogenic organisms, or organisms all pathogenic organisms, or organisms capable of giving rise to infection capable of giving rise to infection

SanitizationSanitization - This term is sometimes used - This term is sometimes used as a synonym for disinfection, particularly as a synonym for disinfection, particularly used with reference to food processing & used with reference to food processing & catering catering

Definitions Definitions

AntisepsisAntisepsis – used to indicate the prevention of – used to indicate the prevention of infection, usually by inhibiting the growth of infection, usually by inhibiting the growth of bacteria in wounds or tissuesbacteria in wounds or tissues

Bactericidal agents Bactericidal agents Bacteriostatic agents Bacteriostatic agents CleaningCleaning Degerming Degerming

HISTORYHISTORY The science of microbiology has shed much light on the nature of The science of microbiology has shed much light on the nature of

disease. In the nineteenth century the work of Pasteur ,Lister and disease. In the nineteenth century the work of Pasteur ,Lister and Koch did much to explain the role of bacteria in disease and to Koch did much to explain the role of bacteria in disease and to indicate possible methods of practicing safer medicine.indicate possible methods of practicing safer medicine.

LOUIS PASTEUR (1822-95) was the first scientist to show clearly LOUIS PASTEUR (1822-95) was the first scientist to show clearly that bacteria never generate spontaneously and that no growth of that bacteria never generate spontaneously and that no growth of any kind occurs in the sterilized media.any kind occurs in the sterilized media.

One of his many achievements was the development of the One of his many achievements was the development of the technique of controlled heating known as ‘PASTEURISATION’ for technique of controlled heating known as ‘PASTEURISATION’ for the preservation of beverages and food stuffs.the preservation of beverages and food stuffs.

Dr. Joseph Lister (Dr. Joseph Lister (1827-1912)1827-1912)

• Discovered the effectiveness of 'carbolic acid,‘ Discovered the effectiveness of 'carbolic acid,‘ which was used in controlling typhoid.which was used in controlling typhoid.

Using carbolic acid, Lister was able to keep his hospital ward in Glasgow free of infection for nine months.

Carbolic acid spray being used at Carbolic acid spray being used at the time of a surgerythe time of a surgery

“ “ The Golden Age of MICROBIOLOGY”The Golden Age of MICROBIOLOGY”

Louis Pasteur (France)Louis Pasteur (France)

Robert Koch (Germany) Robert Koch (Germany)

Oliver Wendell Holmes (USA)Oliver Wendell Holmes (USA)

Lord Joseph Lister (England)Lord Joseph Lister (England)

WHY STERILIZATION IS WHY STERILIZATION IS IMPORTANT IN DENTISTRYIMPORTANT IN DENTISTRY

DiseasesDiseases PathogenPathogen

Herpes infectionsHerpes infections Herpesvirus hominis (herpes Herpesvirus hominis (herpes simplex virus)simplex virus)

SyphilisSyphilis Treponema pallidumTreponema pallidum

Hand-foot-mouth Hand-foot-mouth diseasedisease

CoxsackievirusCoxsackievirus

HerpanginaHerpangina CoxsackievirusCoxsackievirus

Gonococcal Gonococcal pharyngitispharyngitis

Neisseria gonorrhoeaeNeisseria gonorrhoeae

CandidiasisCandidiasis Candida albicansCandida albicans

ORAL DISEASES

I) HERPES INFECTIONS :

- In this disease, vesicle-type lesions can occur in the mouth.

-Vesicles during active herpes simplex infections at any site of the body contain the virus which may be spread to others by direct contact with these lesions.

-Also, the herpes simplex virus may be present in saliva in

those with oral or lip lesions and possibly in a small percent of those who are infected but have no active lesions.

-In such instances, sprays or aeorosols of the saliva may result in spread of the virus to unprotected eyes of the dental team.

II) HERPANGINA AND HAND-FOOT-MOUTH DISEASE :

Herpangina appears as vesicles on the soft palate or elsewhere in the posterior part of the mouth that break down to ulcers that last for about a week. -Fever, sore throat and headache frequently accompany the vesicular stage. -The lesions are caused by specific types of coxackie virus.

III) ORAL SYPHILIS .

Treponema pallidum is a spirochete bacterium and is the causative agent of syphilis.-About 5-10% of the cases of syphilis first occur in the mouth in the form of a lesion called a primary chancre, an open ulcer frequently on the tongue or lips. -These lesions do contain the live spirochetes and may be spread by direct contact.- The possibility of the spirochete entering small cuts or breaks in the skin of unprotected hands and can cause syphilis of the finger.

IV) ORAL CANDIDIASIS :

Candida albicans is a yeast that occurs in the mouth asymptomatically in about one third of adults.-Such circumstances that may result in oral disease called thrush or oral candidiasis might include conditions that disturb our body defense mechanisms such as the systemic diseases of HIV infection, and leukemia;

-Spread of C. albicans from a patient’s mouth to the dental team is theoretically possible through direct contact with lesions or sprays or aerosols of infected saliva.

PREREQUISITESPREREQUISITES FOR AN FOR AN IDEAL DISINFECTANT IDEAL DISINFECTANT AND ROLE PLAYING AND ROLE PLAYING FACTORSFACTORS

Selection of antiseptics & Selection of antiseptics & disinfectants disinfectants

PrerequisitesPrerequisites

It should have a wide spectrum of activityIt should have a wide spectrum of activity Fast acting Fast acting Active in the presence of organic matterActive in the presence of organic matter Nontoxic to animals or humans ( antiseptic )Nontoxic to animals or humans ( antiseptic ) Soluble in water Soluble in water It should not separate on standing It should not separate on standing Should have high penetrating power Should have high penetrating power Surface compatibility Surface compatibility Relatively inexpensive Relatively inexpensive

METHODS OFMETHODS OF MICROBIAL CONTROL MICROBIAL CONTROL

Physical Agents Physical Agents

Chemical AgentsChemical Agents

Chemotherapeutic Chemotherapeutic AgentsAgents

• Heat• Freezing• Radiation• Filtration• Ultrasonic and SonicVibration

PHYSICAL CONTROL WITH HEATPHYSICAL CONTROL WITH HEAT

SUNLIGHTSUNLIGHT – Ultraviolet rays – Ultraviolet rays

Typhoid bacilli exposed to sun on pieces of Typhoid bacilli exposed to sun on pieces of cloth were killed in 2 hours, where the controls cloth were killed in 2 hours, where the controls kept in dark were alive after 6 dayskept in dark were alive after 6 days

DRYINGDRYING - 4/5 - 4/5thth of the bacterial cell is made-up of the bacterial cell is made-up

of water of water

Dry heat Dry heat

DIRECT FLAMEDIRECT FLAME

Bunsen burnerBunsen burner

IncinerationIncineration

HOT AIR OVENHOT AIR OVEN

Radiating dry heat Radiating dry heat 16016000 C ( 320 C ( 32000 F) & 2 Hours F) & 2 Hours useful for sterilizing dry powders, water useful for sterilizing dry powders, water

free oily substances, many types of glass free oily substances, many types of glass ware such as pipettes, flasks, and ware such as pipettes, flasks, and syringes. syringes.

Advantage – non corrosive method Advantage – non corrosive method

Hot air oven Hot air oven

Moist heatMoist heat

Temperatures below 100Temperatures below 10000C/ pasteurizationC/ pasteurization Temperatures at 100Temperatures at 10000C/ boilingC/ boiling Steam at atmospheric pressure Steam at atmospheric pressure

Pasteurization ( below 100Pasteurization ( below 10000C )C )Purpose – To reduce the bacterial population of a Purpose – To reduce the bacterial population of a

liquid such as milk liquid such as milk Spores are not affected by pasteurizationSpores are not affected by pasteurization Holding methodHolding method 62.962.900C for 30 minutesC for 30 minutes Flash pasteurizationFlash pasteurization – 71.6 – 71.600C for 15sec C for 15sec Ultra pasteurizationUltra pasteurization – 82 – 8200C for 3secC for 3sec

BOILING WATERBOILING WATER (100 (10000C)C)

Less time of exposure are required Less time of exposure are required

DenaturationDenaturation of proteins .of proteins .

Minimum exposure time – 30 minutes Minimum exposure time – 30 minutes

Less reliable Less reliable

Washing soda ( 2% conc.) may be added Washing soda ( 2% conc.) may be added

Fractional sterilization ( steam at atmospheric Fractional sterilization ( steam at atmospheric pressure )pressure )

Tyndallization Tyndallization

( John Tyndall ) ( John Tyndall )

IntermittentIntermittent

sterilization sterilization

Free flowing steam at 100Free flowing steam at 10000C for 30 minutes on C for 30 minutes on each of 3 successive days.each of 3 successive days.

First dayFirst day - steam kills all organisms except - steam kills all organisms except spores, and it stimulates spores to germinate spores, and it stimulates spores to germinate vegetative cellsvegetative cells

Second day Second day –vegetative cells are killed –vegetative cells are killed

Third dayThird day – kills the remaining cells – kills the remaining cells

AUTOCLAVEAUTOCLAVE

Moist heat In the form of pressurized steam Moist heat In the form of pressurized steam

increase in the pressure of the gasincrease in the pressure of the gas

increase in the temperatureincrease in the temperature

As the water molecules in steam becomes more As the water molecules in steam becomes more energized, their penetration increases energized, their penetration increases

Used for glassware, metal ware, blankets, Used for glassware, metal ware, blankets, intravenous solutions and a broad variety of intravenous solutions and a broad variety of other objectsother objects

Pressure in autoclave Pressure in autoclave - 15pds/sq. inch- 15pds/sq. inchTemperature Temperature – – 121.5121.500CCTime Time – – 3 to 30 min3 to 30 min

AUTOCLAVEAUTOCLAVE

Limitations Limitations Plastic ware melts in high heat Plastic ware melts in high heat sharp instruments become dull sharp instruments become dull Oily substances cannot be treatedOily substances cannot be treated Prevacuum autoclavePrevacuum autoclave Temperature - 132Temperature - 13200C to 134C to 13400C C Pressure – 28 to 30 lb/1nPressure – 28 to 30 lb/1n22

Time – 4minutes Time – 4minutes Advantage – minimal exposure time for Advantage – minimal exposure time for

sterilization sterilization

HOT OIL HOT OIL

16016000C for 1 hour C for 1 hour

Advantages – no rusting of instrumentsAdvantages – no rusting of instruments

minimal corrosion minimal corrosion SILICON SILICON

Physical control by other Physical control by other methods methods

FILTRATION ( 1980s )FILTRATION ( 1980s )

filter technology – Charles Chamberland filter technology – Charles Chamberland Julius petri Julius petri Filter – a mechanical device used to remove Filter – a mechanical device used to remove

microorganisms from a solution microorganisms from a solution

Ex; IV solutions,bacteriological media, toxoids, Ex; IV solutions,bacteriological media, toxoids, pharmaceuticals etc.pharmaceuticals etc.

Types of filtersTypes of filters Candle filtersCandle filters 1.Unglazed ceramic filters 1.Unglazed ceramic filters

Ex; Chamberland filter Ex; Chamberland filter

2.Diatomaceous earth filters2.Diatomaceous earth filters

Ex; Berkefeld filterEx; Berkefeld filter Asbestos filtersAsbestos filters Sintered glass filtersSintered glass filters Membrane filtersMembrane filters

Membrane filter technique Membrane filter technique

ULTRASONIC LIGHTULTRASONIC LIGHT

Wave lengthWave length

Visible light is between 400 & 800nmVisible light is between 400 & 800nm

Ultraviolet light is between 100 & 400 nmUltraviolet light is between 100 & 400 nm

Mechanism of action

When microorganisms are subjected to UV light linking of thymine molecules occurs

Demerits;

It is not effective against bacterial spores

Does not penetrate liquids or solids

It may cause damage to human cells

Other types of radiationOther types of radiation

Ionizing radiationIonizing radiation X-rays & gamma rays X-rays & gamma rays

Both have wavelengths shorter than the UV lightBoth have wavelengths shorter than the UV lightThey force electrons out of their shells, thereby creating ions They force electrons out of their shells, thereby creating ions

MicrowaveMicrowave

- Wave length is longer than that of UV light- Wave length is longer than that of UV light

- Molecules are set into a high speed motion- Molecules are set into a high speed motion

Laser beamLaser beam

LLight ight AAmplification by mplification by SStimulated timulated EEmission of mission of RRadiation adiation

ULTRASONIC VIBRATIONSULTRASONIC VIBRATIONS High frequency sound waves beyond the range of the High frequency sound waves beyond the range of the

human ear human ear ‘ ‘Cold boiling’ Cold boiling’ They cause the formation of bubbles or cavities and the They cause the formation of bubbles or cavities and the

water appears to boil - water appears to boil - cavitation cavitation DemeritsDemerits Not very effective Not very effective Liquid is required Liquid is required

Chemical control of Chemical control of microorganismsmicroorganisms

• Agents that damage cell membraneAgents that damage cell membrane• Agents that denatures protein

• Agents that modify the functional group of protein & nucleic acid

Destroys structural integrity of cell Destroys structural integrity of cell membrane (protein & lipids).membrane (protein & lipids).

Net effect is the release of small Net effect is the release of small metabolites from the cell that interferes with metabolites from the cell that interferes with the active transport and energy metabolism.the active transport and energy metabolism.

Agents:Agents: Surface active agents Surface active agents

• Cationic – most effectiveCationic – most effective• AnionicAnionic• Non-ionic – not effectiveNon-ionic – not effective• Amphoteric Amphoteric

Phenolic compoundPhenolic compound AlcoholAlcohol

Cationic AgentsCationic Agents Quarternary ammonium compoundQuarternary ammonium compound- Bactericidal for a wide range of organisms, Bactericidal for a wide range of organisms,

gram (+) species are more susceptiblegram (+) species are more susceptible

• Used primarily in hand or face washesUsed primarily in hand or face washes• Acts on phospholipids, changes cell Acts on phospholipids, changes cell

permeability.permeability.• Include in disinfecting instruments and Include in disinfecting instruments and

preserving drugs in low concentration form.preserving drugs in low concentration form.

Anionic AgentsAnionic Agents - Soaps and fatty acid dissociate to yield Soaps and fatty acid dissociate to yield

negatively charged ions (active at acid Ph). negatively charged ions (active at acid Ph).

- Causes gross disruption of the lipoprotein Causes gross disruption of the lipoprotein framework of the cell wall.framework of the cell wall.

- Displays rapid bactericidal action (within Displays rapid bactericidal action (within 30secs) .30secs) .

- Effective against gram (+) organisms.Effective against gram (+) organisms.

Biguanides Biguanides

- Antimicrobial activity against vegetative - Antimicrobial activity against vegetative bacteria, yeasts, and enveloped viruses .bacteria, yeasts, and enveloped viruses .

- Disrupts cytoplasmic membrane.- Disrupts cytoplasmic membrane.

- It may be used together with surface active - It may be used together with surface active agents.agents.

ChlorhexidineChlorhexidine which is more effective atwhich is more effective at

pH 7 – 8 pH 7 – 8 Used as a safe antiseptic to prevent Used as a safe antiseptic to prevent

body infection , in oral rinses for treating body infection , in oral rinses for treating sore gums, mouth ulcers and preventing sore gums, mouth ulcers and preventing plaque on teeth. plaque on teeth.

II Phenolic compound

- At low concentration, causes leakage of cell contents and irreversible inactivation of membrane-bound oxidases and dehydrogenases.

- Parent compound : Carbolic acid ( phenol )Excellent for disinfecting faeces, blood, pus,

sputum & other proteinaceous material.

Primarily used for testing new bactericidal Primarily used for testing new bactericidal agent agent

- CresolsCresols

- XylenolsXylenols

Phenolics are effective against bacteria, Phenolics are effective against bacteria,

fungi and viruses.fungi and viruses.

Kills 99.9% of germs in 30 seconds

• Hospital disinfectant deodorant is highly effective against TB, and HIV-1•It is tuberculocidal, virucidal, fungicidal, bactericidal

• Diphenyl compound - Exhibits unique antibacterial property.- Hexachlorophene

Topical anti-infective, anti-bacterial agent, often used in soaps, toothpaste and antiperspirant .

• Used as a preservative in cosmetic products.

III. Alcohol

- Disorganizes lipid structure by penetrating into the hydrocarbon region, denatures proteins.

-Optimal activity best at 70% - 75% .

- Effective against vegetative bacteria, fungi Effective against vegetative bacteria, fungi and viruses .and viruses .

- Sporicidal activity Sporicidal activity

- Disinfects work surfaces and, as Disinfects work surfaces and, as antiseptics on skin.antiseptics on skin.

Ethanol / Ethyl alcohol

- Used as skin disinfectant. - Uses: Sterilizes skin before cutaneous injections. Disinfects thermometers.- Most effective at 50-70%

-Effective against gram (+) , gram (-) bacteria.

Isopropyl alcohol - Most effective at 50-70%

- Recommended as replacement for the sterilization of thermometers

-Necrosis may result from absorption of vapours through the lungs during alcohol sponge bath.

1.Acid & alkalies –

Benzoic acidLactic acidAcetic acid Propionic acid

2. Alcohol

3. Acetone

Agents:1. Heavy metals2. Oxidizing agents3. Dyes4. Alkylating agents

Heavy Metals • Mercurials

• Mercuric chloride – very toxic disinfectant, not used today.• Metaphen, Merthiolate, Mercuchrome .

• Silver compounds • Soluble silver salts or as colloidal preparations.• Silver nitrate – highly bactericidal for gonococci. • Silver sulfadiazine – topical cream for burn patients.

Oxidizing agent• Halogens

(1) Iodine - As I2 at pH value below 6 where maximal

bactericidal action takes place.

- Destroys many microorganisms and viruses within 3-5 minutes.

- Strong smell and can stain skin and clothing.

- Skin irritant .

Betadine Solution- Iodophores - Enhances stability

- Povidone –iodine

-Available in "Swab Aid" pads, Swab Sticks and as a Surgical Scrub. - It is a fast-acting, broad-spectrum antiseptic .- Indicated for degerming skin, wounds and mucous membranes.- widely use in hospitals, sanitation and water purification.

-

(2) chlorine- Hypochlorite, inorganic ,inorganic chloramines.

- The active moiety of hypochlorites and chlorine is hypochlorous acid.

- Water disinfectant - Hypochlorites - most useful of the chlorine compound

• Hydrogen peroxide

- It is a weak acid.- Used in the cleansing of wounds.- It has strong oxidizing properties and is therefore a powerful bleaching agent that is mostly used for bleaching paper.

Dyes• Triphenyl methane dyes

• Crystal violet, Malachite green, Brilliant green • Highly selective for gram (+) organisms• Used in the laboratory in the formulation of selective culture media

• Acidine dyes • Often referred as Flavines(proflavine, acriflavine) .• Exerts a bactericidal and bacteriostatic effect.• Used in wound antisepsis.

Alkylating agent

- Glutaraldehydes and formaldehydes .

- Active against bacteria and their spores, viruses, fungi and protozoa.

-These effects are mediated predominantly via amine, sulfurhydryl and carboxyl groups on microbial surface proteins.

Formaldehyde:-• Aqueous solution containing 37% formaldehyde (Formalin) • Paraformaldehyde a poymer (contain 91-99% formaldehde)

- Formalin - used for preserving fresh tissues- when used in high concentration, it destroys all organisms, including spores.

- Used to inactivate virus in the Used to inactivate virus in the preparation of vaccines.preparation of vaccines.

- As a gas – used to decontaminate As a gas – used to decontaminate rooms, buildings, fabrics, and rooms, buildings, fabrics, and instruments..instruments..

Glutaraldehyde - used as “cold sterilant” for surgical instruments- 10x more effective than formaldehyde as a bactericidal and sporocidal agent and less toxic.

Ethylene oxide - Employed in gaseous sterilization, especially on materials that would be damaged by heat (polyethylene tubings, drugs).- Active against all types of bacteria, including spores & TB bacilli. f

Causes of sterilization failure Causes of sterilization failure

Improper loading of sterilization chamberImproper loading of sterilization chamber Improper packingImproper packing Improper timingImproper timing improper temperatureimproper temperature Improper cleaning of items to be sterilized.Improper cleaning of items to be sterilized.

CONCLUSIONCONCLUSION

• IT IS OUR MOST IMPORTANT DUTY TO PRESERVE AND MAINTAIN THE HEALTH OF OUR PATIENTS AND OURSELVES.

• WE AND OUR PATIENTS ARE AT ALARMINGLY HIGH RISK OF GETTING INFECTED BY DANGEROUS DISEASES LIKE Hepatitis-B, TB, Herpes, HIV ETC.

• TO PREVENT ALL THESE DEADLY DISEASES AND TO PROTECT OURSELF WE SHOULD TAKE ATMOST PRECAUTION BY FOLLOWING STRICT STERILISATION AND DISINFECTION PROCEDURES.

ReferencesReferences Text book of microbiologyText book of microbiology -R.Ananthnarayan & C.K.J.Paniker-R.Ananthnarayan & C.K.J.Paniker Infection control & office safetyInfection control & office safety - DCNA ( 1991 April )- DCNA ( 1991 April ) Infection control Infection control - C.H.Miller- C.H.Miller Fundamentals of microbiology Fundamentals of microbiology - Edward Alcamo- Edward Alcamo Microbiology Microbiology - W.K.Joklik & H.P.Willett- W.K.Joklik & H.P.Willett

ReferencesReferences Robert.G.cash.-Robert.G.cash.- Trends in sterilization procedures and Trends in sterilization procedures and

disinfection procedures in orthodontic officesdisinfection procedures in orthodontic offices – – AJODO ;1990.Vol.98AJODO ;1990.Vol.98

Gerald.E.SmithGerald.E.Smith -Glass bead sterilization of orthodontic -Glass bead sterilization of orthodontic bands –AJODO; Sept 1986bands –AJODO; Sept 1986

W.F.Hohlt, C.H. MillerW.F.Hohlt, C.H. Miller- Sterilization of orthodontic - Sterilization of orthodontic instruments in cassettes - AJODO; Nov 1990instruments in cassettes - AJODO; Nov 1990

G.M.Mccarthy A.H.MamandrasG.M.Mccarthy A.H.Mamandras - Infection control in the - Infection control in the orthodontic office in Canada - AJODO Sept.1997 orthodontic office in Canada - AJODO Sept.1997

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