Disinfection and sterilizationDisinfection and sterilization

Sterilization: complete removal, destruction, inactivation of all forms of microbial life

viruses, viruses, Fungi,Fungi,bacteria, bacteria, Spores. Spores.

• Disinfection: elimination of most pathogenic organisms excluding sporicidal activity. There are 3 levels;

•HLD, all vegetating bacteria, MTB, fungi, all viruses

•ILD, all vegetating bacteria, MTB, majority of fungi, majority of viruses

•LLD, vegetating bacteria except MTB, some fungi, some viruses

•Antiseptics: chemical disinfectants applied to skin, mm but not systemic

•Cleaning: removal of dust, dirt, organics, FM.

•Decontamination: general term applied to any procedure by which microorganisms are reduced to a level where items are safe to handle

•Antiseptics: chemical disinfectants applied to skin, mm but not systemic

•Cleaning: removal of dust, dirt, organics, FM.

•Decontamination: general term applied to any procedure by which microorganisms are reduced to a level where items are safe to handle

Patient’s care items are divided into 3 Patient’s care items are divided into 3 categories:categories:

Critical itemsCritical items

Semi-critical itemsSemi-critical items

Non-critical itemsNon-critical items

Depending on the risk of infection due to their utilizationDepending on the risk of infection due to their utilization

Critical Semi critical NoncriticalCritical Semi critical Noncritical

Items enter -sterile tissues-cavities-vascular system

e.g. needles, implants, catheters, surgical instruments

Sterilization: EO, autoclave, plasma, sterilant

Items come in contact with intact mm & non intact skin

e.g. endoscopes, endotracheal tube, thermometer

High level disinfectant, glutaraldehyde, chlorine active, hydrogen peroxide

Items come in contact with intact skin

e.g. sphygmomanometers, bed linens, floors

Intermediate and low level disinfectants, alcohols, phenols

Decreasing order of resistance of Decreasing order of resistance of microorganisms to disinfection and microorganisms to disinfection and

sterilizationsterilization ResistantResistant

SusceptibleSusceptible

• Prions Prions

• Bacterial spores Bacterial spores

• MycobacteriaMycobacteria

• Small non-enveloped Small non-enveloped virusesviruses

• Gram-negative Gram-negative bacteria bacteria

• Fungi Fungi

• Large non-enveloped Large non-enveloped virusesviruses

• Gram-positive bacteria Gram-positive bacteria

• Lipid enveloped Lipid enveloped virusesviruses

Decontamination StepsDecontamination Steps

I. HeatI. Heat

1- Moist heat or steam sterilization1- Moist heat or steam sterilization

2- Dry heat sterilization2- Dry heat sterilization

II. Low temperature (cold):II. Low temperature (cold):

1. chemical1. chemical

a. ethylene oxidea. ethylene oxide

b. liquid steriliants: GLD, PAA, H2O2b. liquid steriliants: GLD, PAA, H2O2

2- plasma sterilizer2- plasma sterilizer

III. Other sterilizers:III. Other sterilizers:

1- ionizing radiation1- ionizing radiation

2- filtration2- filtration

3- microwaves; in pharmaceutical 3- microwaves; in pharmaceutical industriesindustries

• Heat is the Heat is the most practical, efficient, and most practical, efficient, and inexpensiveinexpensive method of sterilization and method of sterilization and disinfection of objects that can withstand high disinfection of objects that can withstand high temperaturestemperatures. .

• There are two forms:There are two forms: – Moist heatMoist heat is much is much more efficientmore efficient than dry heat than dry heat

because: because: • it kills microorganisms it kills microorganisms by coagulating and by coagulating and

denaturing their enzymes and structural proteinsdenaturing their enzymes and structural proteins • it is quicker in heating up the article to be sterilized.it is quicker in heating up the article to be sterilized.

– Dry heatDry heat is believed to kill microorganisms by causing is believed to kill microorganisms by causing destructive oxidation of essential cell constituentsdestructive oxidation of essential cell constituents..

Autoclave = Autoclave = saturated water steam under high pressure. saturated water steam under high pressure. heating water under controlled conditions in a closed vessel in heating water under controlled conditions in a closed vessel in order that boiling point of water rises above 100°C. order that boiling point of water rises above 100°C.

Saturated steam carries the same temperature of boiling Saturated steam carries the same temperature of boiling water. water.

It is essential to make steam saturated and free of any It is essential to make steam saturated and free of any residual residual air because air acts as an insulator, reduces temperature and air because air acts as an insulator, reduces temperature and hinders penetration. hinders penetration.

Sterilization temperature and exposure time : Sterilization temperature and exposure time : at 121°C for 20-30 minutes at double atmospheric pressure (2 at 121°C for 20-30 minutes at double atmospheric pressure (2 bar)bar)or at 134°C for 3-6 minutes (at 3 bar). or at 134°C for 3-6 minutes (at 3 bar).

Autoclave = Autoclave = saturated water steam under high pressure. saturated water steam under high pressure. heating water under controlled conditions in a closed vessel in heating water under controlled conditions in a closed vessel in order that boiling point of water rises above 100°C. order that boiling point of water rises above 100°C.

Saturated steam carries the same temperature of boiling Saturated steam carries the same temperature of boiling water. water.

It is essential to make steam saturated and free of any It is essential to make steam saturated and free of any residual residual air because air acts as an insulator, reduces temperature and air because air acts as an insulator, reduces temperature and hinders penetration. hinders penetration.

Sterilization temperature and exposure time : Sterilization temperature and exposure time : at 121°C for 20-30 minutes at double atmospheric pressure (2 at 121°C for 20-30 minutes at double atmospheric pressure (2 bar)bar)or at 134°C for 3-6 minutes (at 3 bar). or at 134°C for 3-6 minutes (at 3 bar).

• Steam sterilization is Steam sterilization is the most common the most common and preferred and preferred method for method for sterilizing those sterilizing those items that can items that can withstand high withstand high temperature and temperature and moisture, e.g. moisture, e.g. culture media, culture media, surgical instruments surgical instruments and dressings.and dressings.

Autoclave:Advantages:

1- Non-toxic2- liberation of latent heat due to condensation of steam3- Inexpensive4- Rapidly microbicidal5- Least affected by organic/inorganic soils6- Rapid cycle time7- Penetrates medical packing, device lumens

Disadvantages:

1- Deleterious for heat labile instruments2- Potential for burns not for powders and oils

Sterilization monitored routinely Sterilization monitored routinely by combination of mechanical, by combination of mechanical, chemical, and biological chemical, and biological parametersparameters

• Physical - cycle time, Physical - cycle time, temperature, pressuretemperature, pressure

• Chemical - heat or chemical Chemical - heat or chemical sensitive inks that change color sensitive inks that change color when germicidal-related when germicidal-related parameters presentparameters present

• Biological - Biological - Bacillus Bacillus spores that spores that directly measure sterilization directly measure sterilization ((Geobacillus stearothermophilus)Geobacillus stearothermophilus)

Chemical IndicatorsChemical Indicators

I.I. Incineration:Incineration:• For dead animal bodiesFor dead animal bodies• Infectious hospital waste Infectious hospital waste

II.II. Red heat: Red heat: for wires, loops, tips of for wires, loops, tips of

forcepsforcepsthey are flamed till they are flamed till

reach rednessreach redness

I.I. Hot air oven:Hot air oven:Dry hot air used either Dry hot air used either 170c for 60 min170c for 60 minor 160c for 120 minor 160c for 120 min

Micro-incineratorMicro-incineratorMicro-incineratorMicro-incinerator

• Hot air ovenHot air oven

- They are electrical devices used in sterilization.

-There is a digitally controlled thermostat controlling the temperature.

- Their double walled insulation keeps the heat in .

- There is also an air filled space in between to aid insulation.

- An air circulating fan helps in uniform distribution of the heat.

- They are electrical devices used in sterilization.

-There is a digitally controlled thermostat controlling the temperature.

- Their double walled insulation keeps the heat in .

- There is also an air filled space in between to aid insulation.

- An air circulating fan helps in uniform distribution of the heat.

Advantage of dry heatAdvantage of dry heat 1. Hot air penetrates certain substances that cannot be 1. Hot air penetrates certain substances that cannot be

steam sterilized (oil, powder). steam sterilized (oil, powder). 2. Dry heat can be used in laboratories to sterilize glassware 2. Dry heat can be used in laboratories to sterilize glassware 3. Dry heat is a protective method of sterilizing no erosion or 3. Dry heat is a protective method of sterilizing no erosion or

corrosion. corrosion. 4. Instruments that cannot be disassembled may be 4. Instruments that cannot be disassembled may be

sterilized in hot air. sterilized in hot air. 5. Low cost 5. Low cost

Disadvantages of dry heatDisadvantages of dry heat 1. A long exposure period is required because hot air 1. A long exposure period is required because hot air

penetrates slowly possibly unevenly. penetrates slowly possibly unevenly. 2. Time and temperature vary for different substances. 2. Time and temperature vary for different substances. 3. Over exposure may ruin some substances. 3. Over exposure may ruin some substances. 4. It is destructive to fabrics4. It is destructive to fabrics and rubber goods and rubber goods

Monitored by B.subtilis sporesMonitored by B.subtilis spores

• Ethylene oxide gas is commonly used to sterilize objects sensitive to Ethylene oxide gas is commonly used to sterilize objects sensitive to

temperatures greater than 60 °C such as plastics, optics and electrics. temperatures greater than 60 °C such as plastics, optics and electrics.

• Ethylene oxide penetrates well, moving through paper, cloth, and some Ethylene oxide penetrates well, moving through paper, cloth, and some

plastic films and is highly effective.plastic films and is highly effective.

• Ethylene oxide sterilizers are used to process sensitive instruments Ethylene oxide sterilizers are used to process sensitive instruments

which cannot be adequately sterilized by other methodswhich cannot be adequately sterilized by other methods

• AdvantagesAdvantages– Very effective at killing microorganismsVery effective at killing microorganisms– Penetrates medical packaging and many plasticsPenetrates medical packaging and many plastics– Compatible with most medical materials not Compatible with most medical materials not

withstanding heatwithstanding heat– Cycle easy to control and monitorCycle easy to control and monitor

• DisadvantagesDisadvantages– Some states require ETO emission reduction of 90-99.9%Some states require ETO emission reduction of 90-99.9%– (inert gas that eliminates explosion hazard) banned after (inert gas that eliminates explosion hazard) banned after

1995 as it is inflammable1995 as it is inflammable– Potential hazard to patients and staff (very toxic and Potential hazard to patients and staff (very toxic and

carcinogenic in animal models)carcinogenic in animal models)– Lengthy cycle (3-6 hrs)/aeration time (18-24hrs)Lengthy cycle (3-6 hrs)/aeration time (18-24hrs)

Monitored by B. subtilis sporesMonitored by B. subtilis spores

Plasma describes any gas that consists of Plasma describes any gas that consists of electrons, ions, or neutral particles. electrons, ions, or neutral particles.

Plasma sterilizers with the use of liquid Plasma sterilizers with the use of liquid peracetic acid, or hydrogen peroxide, or a peracetic acid, or hydrogen peroxide, or a mixture of both are commercially mixture of both are commercially available.available.

The energy used is either microwave The energy used is either microwave frequency or radio-frequency. frequency or radio-frequency.

1- Gamma rays (Co-60).1- Gamma rays (Co-60).

2-High energy electrons (electron accelerator).2-High energy electrons (electron accelerator).

This process does not result in rise in temp; but the

time required for sterilization is long (48hrs).

High penetration power so used in prepacked items, as gloves, High penetration power so used in prepacked items, as gloves, syringes, plastic IV lines,… syringes, plastic IV lines,…

Monitored by B.pumilus sporesMonitored by B.pumilus spores

• Sterilization of Sterilization of fluids which would not fluids which would not withstand heatwithstand heat such as antibiotic such as antibiotic solutions, blood products, hormones, solutions, blood products, hormones, vitamins….etc.vitamins….etc.

• Fluids can be Fluids can be rendered free of bacteriarendered free of bacteria by passage through filters with a by passage through filters with a pore pore size of less than 0.45 µm. size of less than 0.45 µm. – However, However, most viruses and certain most viruses and certain

bacteria as mycoplasma can pass through bacteria as mycoplasma can pass through filters with a pore size as small as 0.22 µm.filters with a pore size as small as 0.22 µm.

Filtration: FluidsFiltration: Fluids

• Early filters made from glass and Early filters made from glass and asbestos asbestos – largely replaced by largely replaced by membrane filtersmembrane filters made made

of cellulose esters or other polymers. of cellulose esters or other polymers.

• Membrane filters are preferred becauseMembrane filters are preferred because::– they filter more rapidly.they filter more rapidly.– they don't affect the filtrate in any way.they don't affect the filtrate in any way.– they adsorb very little of the substance they adsorb very little of the substance

being filtered.being filtered.–

• The endopigment producing The endopigment producing SerratiaSerratia marcescensmarcescens can be used to test the can be used to test the efficiency of bacterial filters.efficiency of bacterial filters.

• Filters can be used to remove Filters can be used to remove microorganisms microorganisms from airfrom air supplied to critical supplied to critical areas such as operating rooms, drug areas such as operating rooms, drug factories and laminar flow ventilation factories and laminar flow ventilation system.system.

• A properly installed A properly installed high efficiency high efficiency

particulate air (HEPA) filterparticulate air (HEPA) filter can achieve can achieve 99.997% 99.997% arrest to particles ≥ 0.5 arrest to particles ≥ 0.5 µµmm, and , and can produce sterile air.can produce sterile air.

• Spores of the fungus Spores of the fungus AspergillusAspergillus can be used can be used to test the efficiency of HEPA filters.to test the efficiency of HEPA filters.

Filt

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Air

1- Chemical disinfection1- Chemical disinfection

2- Boiling water2- Boiling water

3- Pasteurization3- Pasteurization

4- Ultraviolet irradiation4- Ultraviolet irradiation

1- Alcohol 70% (ethyl and isopropyl):1- Alcohol 70% (ethyl and isopropyl):Exposure time:Exposure time: 5 min at least 5 min at least

Uses: Uses: 1- disinfection of 1- disinfection of

a. external surfaces a. external surfaces

b. non invasive instruments b. non invasive instruments

2- skin antiseptic, alone or added to iodine or 2- skin antiseptic, alone or added to iodine or chlorhexidine chlorhexidine

2- Biguanides (chlorhexidine):2- Biguanides (chlorhexidine):1- antiseptic for skin and mm, mouth wash (hexitol)

2- combined with . Alcohol as hand rub

. Detergent as hand wash

3- Chlorine- active compounds (hypochlorite, house hold 3- Chlorine- active compounds (hypochlorite, house hold bleach): bleach):

1- decontamination of blood splashes and lab. Working 1- decontamination of blood splashes and lab. Working surfaces (100-1000ppm)surfaces (100-1000ppm)

2- linen bleaching2- linen bleaching3- disinfection of water3- disinfection of water

4- Iodine based compounds (most effective antiseptics):4- Iodine based compounds (most effective antiseptics):include include - tincture iodine- tincture iodine (iodine in alcohol), staining and (iodine in alcohol), staining and

irritantirritant - iodophores- iodophores (iodine with neutral carrier), slow (iodine with neutral carrier), slow release of free iodine, more penetration, no staining release of free iodine, more penetration, no staining and not irritant, betadine (30-50ppm)and not irritant, betadine (30-50ppm)used as skin antiseptic in surgical scrubbing and used as skin antiseptic in surgical scrubbing and before surgery.before surgery.

Both halogens exert their bactericidal action by irreversible oxidation of the Both halogens exert their bactericidal action by irreversible oxidation of the essential enzymes by the free radicalsessential enzymes by the free radicals

5- Phenol containing preparations (phenol\lysol) ILD:5- Phenol containing preparations (phenol\lysol) ILD:Used for floors, walls and furnitureUsed for floors, walls and furnitureHexaphenol (detol) was used as antiseptic, was proven to Hexaphenol (detol) was used as antiseptic, was proven to cause neurological damagecause neurological damage

6- Quternary ammonium compounds LLD:6- Quternary ammonium compounds LLD:detergent either .anionic as soapdetergent either .anionic as soapor . Cationic as LLDor . Cationic as LLD

.. Used for routine cleaning of walls, floors or furniture.Used for routine cleaning of walls, floors or furniture.

7- Hydrogen peroxide: (oxidizing agent) HLD& sterilants7- Hydrogen peroxide: (oxidizing agent) HLD& sterilants1- antiseptic for open wounds( kill anaerobes)1- antiseptic for open wounds( kill anaerobes)2-disinfection of soft contact lenses, some endoscopes2-disinfection of soft contact lenses, some endoscopes

8- Peracetic acid: (oxidizing agent) HLD& sterilants8- Peracetic acid: (oxidizing agent) HLD& sterilants

HLD, strilizant of instruments as endoscopesHLD, strilizant of instruments as endoscopes9- Glutaraldehyde(cidex) and Formaldehyde HLD& sterilants:9- Glutaraldehyde(cidex) and Formaldehyde HLD& sterilants:

GLD:GLD: HLD, sterilizant of instruments as endoscopes, respiratory and anaesthesia equipments HLD, sterilizant of instruments as endoscopes, respiratory and anaesthesia equipmentsFLD:FLD: gas not used now, found to be carcinogenic, only used in gas not used now, found to be carcinogenic, only used in

sterilization of HEPA filters. sterilization of HEPA filters.

Boiling at 100c for 20 min = HLDBoiling at 100c for 20 min = HLD

Only in emergenciesOnly in emergencies

It is heating at temperature less than 100cIt is heating at temperature less than 100c

1- Pasteurization of milk:1- Pasteurization of milk:

heating at 63c for 30 minheating at 63c for 30 min

or at 72c for 20 sec, this is followed by rapid cooling.or at 72c for 20 sec, this is followed by rapid cooling.

this destroys imp pathogenic bacteria as, MTB, salm, this destroys imp pathogenic bacteria as, MTB, salm, brucella, coxiellabrucella, coxiella

2- Pasteurization of water:2- Pasteurization of water:

heating at 77c for 30 min.heating at 77c for 30 min.

used for disinfection of items canused for disinfection of items can’’t withstand higher t withstand higher temptemp

it may be coupled with chemical disinfection to achieve it may be coupled with chemical disinfection to achieve higher higher level of disinfection or even sterilizationlevel of disinfection or even sterilization

It is heating at temperature less than 100cIt is heating at temperature less than 100c

1- Pasteurization of milk:1- Pasteurization of milk:

heating at 63c for 30 minheating at 63c for 30 min

or at 72c for 20 sec, this is followed by rapid cooling.or at 72c for 20 sec, this is followed by rapid cooling.

this destroys imp pathogenic bacteria as, MTB, salm, this destroys imp pathogenic bacteria as, MTB, salm, brucella, coxiellabrucella, coxiella

2- Pasteurization of water:2- Pasteurization of water:

heating at 77c for 30 min.heating at 77c for 30 min.

used for disinfection of items canused for disinfection of items can’’t withstand higher t withstand higher temptemp

it may be coupled with chemical disinfection to achieve it may be coupled with chemical disinfection to achieve higher higher level of disinfection or even sterilizationlevel of disinfection or even sterilization

UV is a low energy, non ionizing irradiationUV is a low energy, non ionizing irradiation

Its present in sun, artificially produced by mercury Its present in sun, artificially produced by mercury lampslamps

Over exposure may cause eye damage and skin Over exposure may cause eye damage and skin irritationirritation

Have extremely weak penetration powerHave extremely weak penetration power

Used only for:Used only for:Air and surface disinfection inAir and surface disinfection in

Operating roomsOperating rooms

Safety cabinetSafety cabinet