Principle of Sterilization and Disinfectants 2007

5/28/2018 Principle of Sterilization and Disinfectants 2007

1/52

Principle of sterilization anddisinfections

Dr Habsah Hasan

Department of MedicalMicrobiology and Parasitology


2/52

Introduction Infectious disease agents are controlled

by:

Public sanitation measures

Sterilization and disinfection procedures

Chemotherapeutic agents

Bodys defense mechanisms


3/52

Terminology Sterilizationis the complete elimination or

destruction of all forms of microbial life. accomplished in health care facilities by either

physical or chemical processes. Disinfection: process that eliminates many

or all pathogenic microorganisms oninanimate objects, with the exception of

bacterial spores. Disinfection is usually accomplished by the use of

liquid chemicals or wet pasteurization in healthcare settings.


4/52

Terminology When chemicals are used for the purposes of

destroying all forms of microbiologic life,

including fungal and bacterial spores, theymay be called chemical sterilants.

These same germicides used for shorterexposure periods may also be part of the

disinfection process (i.e., high-leveldisinfection).


5/52

TerminologyAntiseptics- disinfectant agents that can

be used on body surfaces, such as skin

or vaginal tract, to reduce the numberof normal flora and pathogeniccontaminants


6/52

Asepsis Processes designed to

prevent microorganismsfrom reaching aprotected environment.

E.g: for proceduresused in

the operating room

the preparation oftherapeutic agents, and

technical manipulation inthe microbiology lab
http://rds.yahoo.com/S=96062857/K=aseptic+technique/v=2/SID=w/TID=SCD_200/l=II/R=70/SS=i/OID=fea582f6e5396d64/;_ylt=A0Je5mwfsjlEphsBJTyJzbkF;_ylu=X3oDMTBxMHZlZTJuBHBvcwM3MARzZWMDc3IEdnRpZANTQ0RfMjAw/SIG=1g08d42qp/EXP=1144718239/*-http%3A//images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Daseptic%2Btechnique%26sm%3DYahoo%2521%2BSearch%26toggle%3D1%26ei%3DUTF-8%26fr%3DFP-tab-img-t%26b%3D61&w=600&h=401&imgurl=www.ratcliffanimalhospital.com%2Fresources%2Fpups%2F_qufrsyx%255b1%255d1.jpg&rurl=http%3A%2F%2Fwww.ratcliffanimalhospital.com%2Fcanine%2520spay%2520-%2520SK%25204-04.htm&size=43.0kB&name=_qufrsyx[1]1.jpg&p=aseptic+technique&type=jpeg&no=70&tt=203&ei=UTF-8http://rds.yahoo.com/S=96062857/K=aseptic+technique/v=2/SID=w/TID=SCD_200/l=II/R=45/SS=i/OID=33abe4e5965e0660/;_ylt=A0Je5mebqDlEwr0AcDOJzbkF;_ylu=X3oDMTBxYm9vYWdlBHBvcwM0NQRzZWMDc3IEdnRpZANTQ0RfMjAw/SIG=1g62jik15/EXP=1144715803/*-http%3A//images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Daseptic%2Btechnique%26sm%3DYahoo%2521%2BSearch%26toggle%3D1%26ei%3DUTF-8%26fr%3DFP-tab-img-t%26b%3D41&w=400&h=432&imgurl=www.cat.cc.md.us%2Fcourses%2Fbio141%2Flabmanua%2Flab2%2Fimages%2Fremoveinoc1_final.jpg&rurl=http%3A%2F%2Fwww.cat.cc.md.us%2Fcourses%2Fbio141%2Flabmanua%2Flab2%2Fatrb.html&size=76.0kB&name=removeinoc1_final.jpg&p=aseptic+technique&type=jpeg&no=45&tt=203&ei=UTF-8http://rds.yahoo.com/S=96062857/K=aseptic+technique/v=2/SID=w/TID=SCD_200/l=II/R=70/SS=i/OID=fea582f6e5396d64/;_ylt=A0Je5mwfsjlEphsBJTyJzbkF;_ylu=X3oDMTBxMHZlZTJuBHBvcwM3MARzZWMDc3IEdnRpZANTQ0RfMjAw/SIG=1g08d42qp/EXP=1144718239/*-http%3A//images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Daseptic%2Btechnique%26sm%3DYahoo%2521%2BSearch%26toggle%3D1%26ei%3DUTF-8%26fr%3DFP-tab-img-t%26b%3D61&w=600&h=401&imgurl=www.ratcliffanimalhospital.com%2Fresources%2Fpups%2F_qufrsyx%255b1%255d1.jpg&rurl=http%3A%2F%2Fwww.ratcliffanimalhospital.com%2Fcanine%2520spay%2520-%2520SK%25204-04.htm&size=43.0kB&name=_qufrsyx[1]1.jpg&p=aseptic+technique&type=jpeg&no=70&tt=203&ei=UTF-8


7/52

Factors influencing efficacy Prior cleaning of the object;

Presence of organic and inorganic load

Type and level of microbial contamination

Concentration of and exposure time to the germicide

The nature of the object (e.g., crevices, hinges, andlumens)

Presence of biofilms

Temperature and pH of the disinfection process

Relative humidity of the sterilizationprocess (e.g.,with ETO).


8/52

Organic materials Organic material (pus, blood, saliva,

urine and feces) protects organisms

from disinfection Hepatitis B virus in organic matter such as

dry blood - resistance to disinfectant


9/52

Resistance organisms Bacterial endospores Most resistance forms

Able to stand 16 hours of boiling

Mycobacteria Cell surface is rich in wax-like lipids causing

resistance to disinfectant but sensitive to heat

Hepatitis virus and HIV Non culturable organismsunable to check post

disinfectants viability

Pseudomonasspp Proliferate in distilled and deionized water

Produce slime that is a barrier to disinfectants.
http://rds.yahoo.com/S=96062857/K=bacterial+endospores/v=2/SID=w/TID=SCD_200/l=II/R=1/SS=i/OID=02c07f2115f1113c/;_ylt=A0Je5mxBszlEgRwBrjGJzbkF;_ylu=X3oDMTBwM3Z0MjNhBHBvcwMxBHNlYwNzcgR2dGlkA1NDRF8yMDA-/SIG=1gv0ph38p/EXP=1144718529/*-http%3A//images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Dbacterial%2Bendospores%26ei%3DUTF-8%26fr%3DFP-tab-img-t%26x%3Dwrt&w=308&h=246&imgurl=www.biologie.uni-hamburg.de%2Fb-online%2Flibrary%2Fmicro229%2Fterry%2Fimages%2Fother%2FB.anthracis1.jpeg&rurl=http%3A%2F%2Fwww.biologie.uni-hamburg.de%2Fb-online%2Flibrary%2Fmicro229%2Fterry%2F229sp00%2Flectures%2Fselect_diseases.html&size=62.6kB&name=B.anthracis1.jpeg&p=bacterial+endospores&type=jpeg&no=1&tt=26&ei=UTF-8


10/52

MethodsPhysical Chemical methods

Heat

Filtration

Radiation

Phenols and phenolics

Alcohols

Halogens

Surfactants

Alkylating agents


11/52

Heat

Moist heat Dry Heat

boiling

Steam under

atmospheric pressure

Steam under


pasteurization

Dry heat sterilization

incineration


12/52

Steam at atmospheric pressure

Steam contains latent heat generated duringvaporization

The latent heat is released when steamcondenses on a colder surface

The condensation release heat and moisturewhich is necessary for protein coagulation to

occur The shrinking of volume of the steam during

condensation creates a negative pressuredrawing in more steam


13/52

Steam under pressure-

Autoclaving To obtain a moist heat temperature of 121 C,

saturated steam is placed under pressure of15 lbs per square inch and sterilizationachieved after 15 minutes

The required time of exposure diminished asthe temperature increased126C10 mins

Sterilization indicator chemical changes

Chemical imprinted on tapes and wrappers

culture testing for spores Bacillus stearothermophilus impregnated in ampoules or

filter paper strips


14/52


15/52

Pasteurization Utilizes mild heat to destroy pathogenic

vegetative forms in liquids without alteringthe liquids palatibility

Used in cows to prevent infectious diseaseassociated with raw milktuberculosis,brucellosis, Camylopbacteriosis, dysentry, Qfever

Two methods Holding/Batch method

Milk in vessels is pasturised at 620C for 30 minutes

Flash/continuous flow method Thin films of milk stream over pipe or plates held at 71.7

C for 15 seconds.


16/52

Moist HeatOrganisms Temperature Time

Most vegetative form of bacteria,yeast and mould, viruses

600C 30 minutes

Most vegetative form of bacteria,yeast and mould, viruses

800C 5 to 10minutes

Mould spores 800C 30

minutesBacterial spores 121 15 mins

Comparison of various conditions required to kill Microorganisms


17/52

Methods sporocidal disinfection sterilization

Boiling x X

Steam(atmosphericpressure)

x X

Steam(under pressure)

NA

Pateurization X X


18/52

Heat

Moist heat Dry Heat

boiling

Steam under


Steam under


pasteurization

Dry heat sterilization

incineration


19/52

Dry heat Biomolecules exhibit less

thermosensitivity to dry heat than to

moist heat Dry heat is slower and requires

temperatures higher than those used in

moist heat


20/52

Dry heat sterilization Used at 1600C for 2 hours or 1700C for 1 hour

Dry heat temperature below 1400C do not

destroy spores within a reasonable timeperiod.

Mechanically convected ovens are used forevenly distributed heat

Method of choice for sterilizing powders, oils,and thermostable materials that are adverselyaffected by moisture


21/52

Incineration Used for discardable,combustible items

such as mask, gloves and wipes that

are soilde with blood and body fluid Flaming is a convenient way to

sterilized inexpensive heat tolerant

implements


22/52


Heat

Filtration

Radiation


Alcohols

Halogens

Surfactants

Alkylating agents


23/52

Filtration Porous material to remove organisms

Applications of filters

Sterilization of liquids and air

Separation of microorganisms of differentsizes

Preparation of cell-free solutions of toxins,antigens

Determination of virus size


24/52

Membrane filters Paper thin,sieve like elements composed of inert

cellulose esters

Pore size range differs (0.005 to 1 m) Pore size of 0.2 micron able to filter bacteria

Filters can be visualized under microscope or cultured

E.g High efficiency particulate air filters (HEPA) filters to filter

particles in the air Reduce particles as small as 0.3 micron with 99.97%

Sterilized serum


25/52


Heat

Filtration

Radiation


Alcohols

Halogens

Surfactants

Alkylating agents


26/52

Radiation Ultraviolet radiation

Ionizing radiation


27/52

Ultraviolet radiation Causes damage to DNA of the microorganisms

UV lamps- generate UV rays with wavelenth 240nmto 280nm

Application- to reduce microorganisms in air andsurfaces of hospital rooms, operating rooms,entryways, nurseries, gymnasium and cafaterias.

Problems-

Low penetrability. Organisms must be directly exposed to UV Overexposure to UV in human, causes skin erythema and

conjunctivitis


28/52

Ionizing radiation Cobalt 60 produces cathode rays and gamma

rays

Advantage Avoid heat and moist

Allows prepackaging and sealing of items to besterilized

Application Sterilizing pharmaceuticals and disposable medical

supplies such as syringes and catheters.

Disadvantagefabrics tensile strength will be

reduced after irradiation


29/52


Heat

Filtration

Radiation


Alcohols

Halogens

Surfactants

Alkylating agents


30/52

Chemical methods All chemicals used in sterilization and

disinfection are grouped as disinfectants.

Chemicals used for sterilization (underprescribed condition) are called sterilants orchemosterilizers

Chemical sterilants include Ethylene oxide (ETO) Formaldehyde and glutaryldehyde


31/52

Ideal properties of disinfectant Able to destroy all forms of microorganisms

within practical period

Soil will not interfere with its reaction Nonirritating, non allergenic and non toxic

Non corrosive and non discolouring

Demonstrate wettability and penetrability

Soluble in water Chemically stable

Dilution will not adversely affect its activity

Do not have disagreeable odour or expensive


32/52

Non of disinfectants meets all thequalification

Disinfection must be chosen on thebasis of their intrinsic properties and jobat hand.


33/52

Classes of disinfectants Phenol and phenolics

Alcohols

Halogens

Surfactants

Alkylating agents


34/52

Phenols and phenolics Properties:

have active compounds in the presence of organic matter

Stable and persist on surface for a long period. Inactivated by rubber, wood and plastics

Use: disinfecting saliva, feces and similar matter

Disadvantage: irritant to skin,

Diphenyl compounds used as skin disinfectant:hexachlorophene and chlorhexidine


35/52

Chlorhexidine Greater bactericidal activity than

hexacholorophene

4% chlorhexidine used for surgical scrub,hand washing and wound cleansing

Persist on the skin, non irritating, notabsorbed

Action is neutralized by soaps and anionicdetergents
http://rds.yahoo.com/S=96062883/K=chlorhexidine/v=2/SID=w/l=IVI/;_ylt=A0Je5wseujlEPxgBat2jzbkF;_ylu=X3oDMTBsZDVtbHJqBHNlYwNwcm9mBHZ0aWQDU0NEXzIwMA--/SIG=12cc17lig/EXP=1144720286/*-http%3A//www.petplace.com/articles/images/190962563thm.jpg


36/52

Alcohols Contact time is important for action

Properties:

High antimicrobial properties on environmentalsurfaces

Use: skin and surface disinfectants

Disadvantage: Dilution reduce the

effectiveness, volatile, flammable and irritatesskin

Examples: Ethyl and isopropylalcohol70%


37/52

Halogens Examples: Chlorine and iodine


38/52

Chlorine Use: sanitation, purification and disinfection.

Elemental chlorinewater purification

Hypochloritesanitizing agents Concentration:

Less than 1 ppm- lethal to most vegetativebacteria, inactivates most viruses

5% sodium hypochloritesurface and glasswaredecontamination

Disadvantage:organic matters interfere withits activities


39/52

Iodine Active compound: tincture of 2% in 50% alcohol Use:

wound and skin antisepsis

Preoperative skin antisepsis General disinfectants for thermometers and surgical

appliances

Disadvantage: cause tissue necrosis in strong concentration Stain skin

Povidone iodine has less tissue necrosis because theiodine is solubilized in povidone which provide asustained released of iodine
http://rds.yahoo.com/S=96062857/K=povidone+iodine/v=2/SID=w/TID=SCD_200/l=II/R=20/SS=i/OID=ed2b643fcd21789a/;_ylt=A0Je5x.ruTlEvVIAV7.JzbkF;_ylu=X3oDMTBxYzZiMWJsBHBvcwMyMARzZWMDc3IEdnRpZANTQ0RfMjAw/SIG=1f5n44tlq/EXP=1144720171/*-http%3A//images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Dpovidone%2Biodine%26ei%3DUTF-8%26fr%3DFP-tab-img-t%26x%3Dwrt&w=123&h=246&imgurl=www.nelsonwholesale.com%2Finventory_poultry%2FProducts%2FRemedies%2FDPC1100_Povidone_Iodine.jpg&rurl=http%3A%2F%2Fwww.nelsonwholesale.com%2Finventory_poultry%2Fpltremedy01.htm&size=4.9kB&name=DPC1100_Povidone_Iodine.jpg&p=povidone+iodine&type=jpeg&no=20&tt=334&ei=UTF-8


40/52

Surfactants Examples

Anionic detergents (Soaps)

effective cleansers, little direct antibacterial effect Cationic detergents (quartenary ammonium

compounds)

highly bactericidal, inactive against spores and virus

Adsorbed into cotton, cork, dustbecomes inactive

Little toxicity to skin and mucous membrane

E.g. benzalkonium chloride


41/52

Alkylating agents Formaldehyde

Glutaryldehyde

Ethylene oxide


42/52

Formaldehyde Use:

gas state as fumigants to decontaminate

room or laboratory that have beenaccidentally and extensively contaminatedwith pathogenic bacteria

Liquid as formalin

Disadvantage: tissue irritant


43/52

Glutaryldehyde Activity: wide spectrum. 2% solution is

bactericidal, tuberculocidal and virucidal in 10to 90 minutes, sporocidals in 10 hours

Effective sterilizing agent for apparatus thatcannot be heat treated such as lensinstrument, equipment for respiratory therapy

Disadvantage: not use as skin antisepsisbecause irritation to skin and soft tissue.

Commercially available: cidex


44/52

Ethylene oxide Cyclic ether

Advantage: It can sterilized without high level

of heat and moisture Usage: catheters, disposable medical items,

dental handpieces, sutures

Disadvantage: toxic if inhaled, vesicant on

contact, slow acting, require 4 hours at 50 to56 C or 6 to 12 hours at room temperature toproduce sterility


45/52


46/52

Vegetativebacteria

Fungi envelopedvirus

Non-enveloped virus Mycobacteria Bacterial spores

Phenol andphenolics

X X

Alcohols +/- X

Iodine

Chlorine X

Chlorhexidine 4%


47/52

Vegetativebacteria

Fungi envelopedvirus

Non-enveloped virus Mycobacteria Bacterial spores

Quartenaryammoniumcompound

+/- X X X

Formaldehyde

Glutaryldehyde (2%)

(10-90 mins)

(10-90

mins)

(10-90

mins)

(10-90 mins)

(10-90

mins)

(10 hours)

Ethyleneoxide


48/52

Disinfectant High-level disinfectants -At similar concentrations

with chemical sterilants but with shorter exposureperiods (e.g., 20 minutes for 2% glutaraldehyde),these same disinfectants will kill all microorganismswith the exception of large numbers of bacterialspores

Low-level disinfectantsmay kill most vegetativebacteria, some fungi, and some viruses in a practicalperiod of time (


49/52

Mode of actionMoist Heat Coagulation of protein of the

microorganism, death- inactivationof enzymes, changes in nucleicacids and cytoplasm

Dry heat Alteration of protein by oxidation,desiccation and changes of osmoticpressure

Filtration Porous material to remove

organisms

Radiation damage to DNA of themicroorganisms


50/52


51/52

STERILIZATION AND DISINFECTION TECHNIQUES COMMONLY USED IN HOSPITAL PRACTICE

Objective Method Principle of microbialinactivation Example of use

Sterilization

Steam autoclaving Thermal denaturation Metallic surgical instrumentsEthylene oxide Thermochemical denaturation Heat-labile surgicalinstruments

Gamma-irradiation Ionizing denaturation Implantable medical devices(catheters, protheses)Gas plasma Generated free radicalinduced denaturation Heat-labile instruments

Disinfection

Chlorine Chemical denaturation Water disinfectionAlcohols Chemical denaturation Skin antisepsisIodophors Chemical denaturation Skin and mucosae antisepsisAldehydes Chemical denaturation Flexible endoscopesPeracetic acid Chemical denaturation Flexible endoscopes

Common sterilization technique


52/52

Common sterilization techniqueA: Heat sterilization, including steam or hot air (steam sterilizationprocessing time

from 3 to 30 minutes).B: Ethylene oxide gas ( generally 1 to 6 hours processing time plus aeration time of 8

to 12 hours at 50to 60C).C: Hydrogen peroxide gas plasma (Processing time between 45 and 72 minutes; for

endoscope or medical device restrictions based on lumen internal diameter and

length)D: Glutaraldehyde-based formulations (> 2% glutaraldehyde; caution should beexercised with all glutaraldehyde formulations when further in-use dilution is

anticipated); glutaraldehyde (0.95%) and 1.64% phenol/phenate. One

glutaraldehyde-based product has a 5 minute exposure time at 35C.E: Ortho-phthalaldehyde 0.55% (FDA cleared as high-level disinfectant; passes the

Sporicidal Activity Test in 32 hours at 20C but not cleared as a chemical

sterilant).F: Hydrogen peroxide 7.5% (will corrode copper, zinc, and brass).G: Peracetic acid; concentration variable but 1% or less is sporicidal. Peracetic acid

immersion system operates at 50to 56C.H: Hydrogen peroxide (7.35%) and 0.23% peracetic acid; hydrogen peroxide 1% and

peracetic acid 0.08% (will corrode metal instruments).

Principle of Sterilization and Disinfectants 2007

Documents

Transcript of Principle of Sterilization and Disinfectants 2007