KMU (IPM&R) pathology

1. Sterilization and DisinfectionSterilization and Disinfection

2.  SterilizationSterilization is the killing or removal ofis the killing or removal of
all microorganisms, including bacterialall microorganisms, including bacterial
spores. It is an absolute germ free state.spores. It is an absolute germ free state.
 DisinfectionDisinfection is the killing of many butis the killing of many but
not all, microorganisms. Speciallynot all, microorganisms. Specially
bacterial spores are not killed.bacterial spores are not killed.
 DisinfectantDisinfectant is a chemical agent that isis a chemical agent that is
used for disinfection.used for disinfection.

3. Methods of sterilization:Methods of sterilization:
I. HeatI. Heat
II. Ionizing radiationsII. Ionizing radiations
III. FiltrationIII. Filtration
IV. ChemicalsIV. Chemicals
I.I. HeatHeat::
It can be againIt can be again
a. Dry heata. Dry heat
b. Moist heatb. Moist heat
c. Pasteurizationc. Pasteurization

4. a.a. Dry HeatDry Heat::
 Sterilization by dry heat requiresSterilization by dry heat requires
temperatures in the range of 180°C for 2temperatures in the range of 180°C for 2
hours.hours.
 Used primarily for glassware.Used primarily for glassware.
 Used less frequently than autoclaving.Used less frequently than autoclaving.
 Dry heat can be applied byDry heat can be applied by
i.i. Red heat:Red heat:
The article to be sterilized is directly held inThe article to be sterilized is directly held in
the flame and heated till it becomes red hot.the flame and heated till it becomes red hot.
ii.ii. Hot air oven:Hot air oven:
 Articles are sterilized in hot air oven at tempArticles are sterilized in hot air oven at temp
range of 160range of 16000
C-180C-18000
C.C.

5.  16016000
C is sterilization temperature.C is sterilization temperature.
 Uses: Glassware, sealed containers. etcUses: Glassware, sealed containers. etc
are sterilized by this method.are sterilized by this method.

6. b.b. Moist heatMoist heat::
 It can be applied byIt can be applied by
1.1. BoilingBoiling
2.2. SteamingSteaming
1.1. BoilingBoiling::
 Simple boiling is used to sterilize someSimple boiling is used to sterilize some
glassware.glassware.

7.  Boiling done for 20-30 minutes forBoiling done for 20-30 minutes for
three consecutive days is calledthree consecutive days is called
Tyndalization. It is used for materialsTyndalization. It is used for materials
which can not withstand prolongedwhich can not withstand prolonged
boiling.boiling.
2.2. SteamingSteaming
 Most common method to be used. It isMost common method to be used. It is
normally applied above 100normally applied above 10000
C underC under
high pressures. The instrument usedhigh pressures. The instrument used

8.  Principle of autoclavingPrinciple of autoclaving::
 In autoclave steam or moist heat isIn autoclave steam or moist heat is
produced at a temp of 115produced at a temp of 11500
C.C.
 Water boils at 100Water boils at 10000
C. At this temp vapourC. At this temp vapour
pressure equals the atmospheric pressurepressure equals the atmospheric pressure
i.e. 760 mm Hg. When water is heated ini.e. 760 mm Hg. When water is heated in
a closed vessel the vapour pressure risesa closed vessel the vapour pressure rises
with a subsequent rise in boiling point.with a subsequent rise in boiling point.
The boiling point rises to 115The boiling point rises to 11500
C.C.

9.  Thus steam produced at this temp isThus steam produced at this temp is
super heated.super heated.
 This steam when condenses on theThis steam when condenses on the
articles thermal energy is released fromarticles thermal energy is released from
it and along with moisture this heatit and along with moisture this heat
denatures the microbial proteins.denatures the microbial proteins.
 Autoclave is used to sterilize most of theAutoclave is used to sterilize most of the
instruments and culture media.instruments and culture media.

10.  Different temperatures for autoclave atDifferent temperatures for autoclave at
different pressures.different pressures.
 11511500
C at 10 psiC at 10 psi
 12112100
C at 15 psiC at 15 psi
 13213200
C at 27 psiC at 27 psi

11. Stovetop autoclaves—the
simplest of autoclaves

12. Dental autoclave

13. c.c. PasteurizationPasteurization::
 It is used primarily for milk.It is used primarily for milk.
 It consists of heating the milk to 62°CIt consists of heating the milk to 62°C
for 30 minutes followed by rapid coolingfor 30 minutes followed by rapid cooling
 OR heating it at 72OR heating it at 7200
C for 20 seconds.C for 20 seconds.
 This is sufficient to kill the vegetativeThis is sufficient to kill the vegetative
forms of the milk-borne pathogens, e.g.forms of the milk-borne pathogens, e.g.
Mycobacterium bovis, Salmonella,Mycobacterium bovis, Salmonella,
Streptococcus etcStreptococcus etc

14. II.II. Ionizing radiationsIonizing radiations::
 The three types of radiation used to killThe three types of radiation used to kill
microorganismsmicroorganisms
 1.Ultraviolet (UV) light and 2. X-rays. 3.1.Ultraviolet (UV) light and 2. X-rays. 3.
Gamma raysGamma rays
 Used in industry to sterilize disposableUsed in industry to sterilize disposable
syringes, gloves, catheters etc.syringes, gloves, catheters etc.
III.III. FiltrationFiltration::
 Filtration is the preferred method of sterilizingFiltration is the preferred method of sterilizing
certain solutions, e.g. IV fluids. Antibioticcertain solutions, e.g. IV fluids. Antibiotic
solutions.solutions.
 Cellulose acetate membrane filter mostCellulose acetate membrane filter most
common.common.
 Pore size 0.02-1 µm. Removes bacteria.Pore size 0.02-1 µm. Removes bacteria.

15.  High-efficiency particulate air (HEPA)High-efficiency particulate air (HEPA)
filters remove almost all microorganismsfilters remove almost all microorganisms
larger than about 0.3 micron in diameter.larger than about 0.3 micron in diameter.
 They are used to remove microThey are used to remove micro
organisms from air. Used specially in TBorganisms from air. Used specially in TB
labs.labs.

16. Filter sterilization with a disposable, presterilizedFilter sterilization with a disposable, presterilized
plastic unit.plastic unit.

17. IV.IV. ChemicalsChemicals: They can be: They can be
a. Gases like Ethylene dioxide used ina. Gases like Ethylene dioxide used in
plastic industry. Highly toxicplastic industry. Highly toxic
inflammable ,potentially explosiveinflammable ,potentially explosive
gas .gas .
b. Liquids like Glutraldehyde used tob. Liquids like Glutraldehyde used to
disinfect endoscopes.disinfect endoscopes.

18.  Methods of DisinfectionMethods of Disinfection::
 DisinfectantsDisinfectants are strong chemicals usedare strong chemicals used
for disinfecting non living articles.for disinfecting non living articles.
 They are toxic and corrosives for livingThey are toxic and corrosives for living
tissues.tissues.
 AntisepticsAntiseptics::
 Disinfectants which are less irritant andDisinfectants which are less irritant and
can be applied to living tissues are calledcan be applied to living tissues are called
antiseptics e.g. methylated spirit,antiseptics e.g. methylated spirit,
Alcohol, Iodine, Chloroxylenol (dettol)Alcohol, Iodine, Chloroxylenol (dettol)

19.  Types of Disinfectants.Types of Disinfectants.
1.1.Phenol and Phenolic compoundsPhenol and Phenolic compounds..
 Phenol (carbolic acid) and phenolics arePhenol (carbolic acid) and phenolics are
good disinfectants.good disinfectants.
 Phenolics are derivatives of Phenol.Phenolics are derivatives of Phenol.
 Cresols is derived from coal tar form anCresols is derived from coal tar form an
important group of phenolics.important group of phenolics.
2.2.BisphenolsBisphenols::
 Bisphenols are derivatives of phenol.

20.  Hexachlorophene and Triclosan areHexachlorophene and Triclosan are
important bisphenols.important bisphenols.
3.3. Biguanides:
 The best known biguanide is
chlorhexidine used for microbial control
on skin and mucous membranes.
 Hibiscrub (chlorhexidine + cetrimide )Hibiscrub (chlorhexidine + cetrimide )
Hibisol (chlorhexidine + glycerine)Hibisol (chlorhexidine + glycerine)

21. 4.4. Halogen compoundsHalogen compounds..
 The halogens, particularly iodine andThe halogens, particularly iodine and
chlorine, are effective antimicrobialchlorine, are effective antimicrobial
agents.agents.
 TheThe most common commercialmost common commercial
preparation of Iodine is povidone-iodinepreparation of Iodine is povidone-iodine
(Pyodine).(Pyodine).
 A liquid form of compressed chlorine gasA liquid form of compressed chlorine gas
used extensively for disinfectingused extensively for disinfecting
municipal drinking water, water inmunicipal drinking water, water in
swimming pools, and sewage.swimming pools, and sewage.

22. 3.3. Aldehydes:Aldehydes:
 Formaldehyde as gas used to sterilizeFormaldehyde as gas used to sterilize
operation theatres and other spaces.operation theatres and other spaces.
 Glutaraldehyde a chemical relative ofGlutaraldehyde a chemical relative of
formaldehyde less irritating and moreformaldehyde less irritating and more
effective than formaldehyde.effective than formaldehyde.
 Glutaraldehyde used to disinfect hospitalGlutaraldehyde used to disinfect hospital
instruments, including endoscopes andinstruments, including endoscopes and
respiratory therapy equipmentrespiratory therapy equipment

23. 4.4. AlcoholAlcohol::
 Alcohols effectively kill bacteria andAlcohols effectively kill bacteria and
fungi but not spores and non envelopedfungi but not spores and non enveloped
viruses.viruses.
 Most commonly used alcohols areMost commonly used alcohols are
ethanol and Isopropanol.ethanol and Isopropanol.
 The recommended conc. of ethanol isThe recommended conc. of ethanol is
70%70%
 Isopropanol is slightly superior toIsopropanol is slightly superior to
ethanol as an antiseptic and disinfectantethanol as an antiseptic and disinfectant
 However, alcohols are unsatisfactoryHowever, alcohols are unsatisfactory
antiseptics when applied to wounds.antiseptics when applied to wounds.