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1. AYSHA MUHSINA V T
MSC BIOLOGY
SNGC CHELANNUR

2. STERILIZATION
 Sterilisation is the is the process by which all living
cells viable spores, viruses and viroids are either
destroyed or removed from an object or habitate
 The word sterilisation is derived from a latin word
‘sterilis’ which means unable to produce offspring
or barrent
 Sterile object is totally free of viable micro
organisms ,spores and other infectious agents
 Sterilisation is achieved by a chemical agent , the
chemical is called sterilant

3.  Antisepsis
1. Prevention of infection or sepsis.
2. These are the chemical agents applied to
tissue to prevent infection by killing or
inhibiting pathogen growth also reduse
total microbial population.
3. Used on living tissue

4. Cidal agent
 Substance that kill organisms
 Germicide kill pathogens but not endospores
 Latin cida means ‘ to kill ‘
Static agents
Chemicals that prevent growth of this agents are
removed , growth will resume.
Eg: bacteriostatic ,fungistatic.

5. CLASSIFICATION
 PHYSICAL METHODS
 CHEMICAL METHODS

6. PHYSICAL AGENTS
 Sun light
 Drying
 Heat
dry heat: flaming, incinaration, hot air oven
moist heat :pasteurization ,boiling, steam under
pressure.
 Filtration
 Radiation

7. Chemical agents
 Alcohols
 Aldehydes
 Halogens
 Phenolics
 Gases
 Chlorine
 Quaternary ammonium compounds
 Heavy metals

8. Physical methods of sterilisation
 Sunlight
Action primarily due to UV rays , effect vary due to
places.
E g ; bacteria in water are readily destroyed by
by sunlight.
 Drying
moisture is essential for growth of bacteria.
drying in air effect on bacteria.
spores are uneffected.

9. Heat
 heating is most popular ways to destroy
microorganisms
 Moist heat readily kills viruses ,bacteria, and fungi
 Boiling can be used for disinfection of drinking
water and objects not harmed by water .But boiling
does not sterilize.
 Exposure to boiling water for 10 minutes is
sufficient to destroy vegetative cells and eukaryotic
spores.

10. Factors effecting by heat
sterilisation
 Nature of heat dry or moist
 Temperature and time
 Number of microorganisms present
 Type of material from which organism have to be
eliminated.
 Killing effect of moist heat due to denaturation and
coagulation of proteins.

11. Moist heat sterilization
Categorized into 3 groups.
Temperature below 100 C
o pasteurization
o Hot water bath-
Temperature at 100 C
o Boiling
Temperature above 100 C
o Steam under pressure autoclave

12.  Pasteurisation
process of killing pathogens in the milk.
material is heated with 63 C for 30
minutes .developed by Luis pasteur
This is a Holder method.
 Flash pasteurisation/HTST
heat at 72 C for 15 to 20 seconds then
rapid cooling at 13 C.

14. Hot water bath
 Inactivate non sporing bacteria
 For the preparation of vaccines-special
vaccine bath at 60 c 1 hour is used
 serum or body fluids containing coagulable
proteins can be sterilised by heating for 1 h r at 56
C in a water
bath for several successive days.

15.  Temp at 100 C
Boiling
 This process kills vegetative forms of bacterial
pathogens.
 Hepatitis virus can survive up to 30 minutes of
boiling.
 Endospores can survive up to 20 hrs or more
boiling.

16.  Temp above 100 C
Autoclave
 Autoclave was designed by Charles chamber land
in 1879.
 Works on the principle of steam under
pressure
 Depends on the cylinder two types vertical and the
horizontal autoclaves
 Like a fancy pressure cooker

17.  Water is boiled to produce steam which is
released through the jacket and into autoclaves
chamber
 The air is initially present in the chamber
is forced out until the chamber is filled
with saturated steam enter until
chamber reaches 121 C and 15 l b s of
pressure
 At this temp. saturated steam destroys all
vegetative cells and endospores.

19. Dry heat sterilisation
 Used to sterilise materials that can with stand
high temperature
 Sterilised in the absence of water
 The items to be sterilised are placed in an oven at
160 to 170 C for 2-3 hrs
 Microbial death apparently results from the
oxidation of cell constituents and denaturation of
proteins.
 Dry heat less effective than moist heat

20.  E g :Clostridium botulinum spores are killed in 5
min.at 121 C by moist heat but only after 2 hrs at
160 C with dry heat.
 It can be used to sterilize powders, oils and similar
items, in lab to sterilise glass petridishes and
pipettes
 It is slow and not suitable for heat sensitive
materials like plastic and rubber

21. Flaming
 heating over fire, till they become red hot.
 Instruments like: point of foreceps, spatulas,
inoculating loops and wires
Incineration
 It is a process that involves the combustion
of organic materials.
 Items contaminated cloth ,animal carcasses and
pathological material.

22. • Flaming Incineration

23. Hot air oven
 Hot air ovens are electrical devices used in
sterilization.
 The oven uses dry heat to sterilies article.
 They can be operated at 50 to 300 C.
 Present thermostat controlling the temperature.
 This is the most widely used method of
sterilization by dry heat.
 Suitable to use in laboratory environment.

26. Filtration
 It is excellent way to reduce microbial populations
in solutions of heat sensitive material and to
sterilize solutions. Eg: sera ,solution of sugar
,antibiotics
 Types of filters
 candle filters
 asbestos filters
 depth filters
 membrane filters
candle filters :used to purification of industrial and
drinking purposes.

27.  These are manufactured under different grades of
porosity use water house purposes ,low cost
Asbestos filters
 Disposable , single –used disc.
 Tend to alkalinise filtered liquids.
Usage is discouraged because of its carcinogenic
Property. carcinogenic, used in cigarette
 Depth filter
Consist of fibrous or granular materials that have
been bonded in to a thick layer filled with twisting
channels of small diameter

28.  The solution containing micro organisms is sucked
through this layer under vacuum , and microbial
cells are removed by physical screening and by
adsorption to the surface of filter material.
 Depth filter are mode of diatomaceous earth
,unglazed porcelain ,asbestos or other similar
material
 Membrane filter
circular filter or porous membrane, a little over 0.1
mm thickness ,made of cellulose acetate,cellulose
nitrate ,poly carbonate,polyvinylidenefluoride etc.

29.  These filters are used to sterilize pharmaceuticals
ophthalmic solutions, culture media, oils,
antibiotics and other heat sensitive solutions
 Air can also be sterilised by filtration

30. CANDLE ASBESTOS

31. MEMBRANE FILTER

32. Radiation
 Two types of radiation
Ionising radiation
Non ionising radiation:
 Infra red-used for rapid mass sterilisation of pre
packed items such as syringe ,catheters
 UV
 Used for disinfecting enclosed area such as
entryways, operation theatres and labs.

33.  Ionising radiation
gamma rays
X-rays
used for sterilising plastics ,syringes, swabs,
catheters ,animal feeds ,card board, oils ,greases, fabric
and metal foils.
U V Radiation
 UV lamps are placed on ceiling of rooms or in
biological safety cabinets to sterilise the air and any
exposed surface.

34.  Commercial UV units are available for water
treatment
 Gamma radiations
from a cobalt 60 source is used in the cold
sterilisation of antibiotics , hormones, plastic
disposable supplies. Such as syringes.
 also used to pasteurize milk and food.

35. Chemical agents
 Action of chemical agents
1. protein coagulation
2. disruption of cell membrane
3. substrate competition .
Alcohols
 Most widely use disinfectants and antibiotics
 Bactericidal ,fungicidal but not sporicidal
 Some liquid containing viruses are also destroyed
.
 Two most popular alcohol germicides are ethanol
and isopropanol used in concentration of 70-80%.
 Act by denaturing proteins and dissolving
membrane lipids.

36. Aldehydes
 Formaldehyde and glutaraldehyde are
highly reactive molecules that combine
with nucleic acid and proteins and
inactive them.
 Sporicidal
 Formaldehyde is dissolve in water
 2 % buffer solution of glutaraldehyde is
an effective disinfectant.

37. Halogens
 Any of F , Cl ,Br ,I
 I And Cl are important antimicrobial agents
 Iodine
skin antiseptic
kills by oxidising cell constituents and
iodinating cell proteins
at higher concentration it may be kills
spores .
Brands :wescodyne-skin and laboratory
disinfectant
betadine-wounds

38. Phenolics
 First widely used antiseptic and disinfectant
 In 1867 Joseph Lister employed it to reduce risk of
infection during operations
 Phenol and phenolics are made up of labs and
hospitals.
 Commercial disinfectant lysol is made up of a
mixture of phenolics.
 Phenolics act by denaturing proteins and
disrupting cell membranes

39. Sterilising gases
 Heat sensitive item such as disposable plastic
petridishes and syringes are sterilised with
ethylene oxide gas is both microbicidal and
sporicidal and kills by combining with cell proteins.
 Effective , rapidly penetrates
 Sterilization is carried out in a special ethylene
oxide sterilizer, resembling autoclave.

40. Chlorine
 For municipal water supplies ,swimming pools
 Also in diary and food industries.
 Applied as chlorine gas, sodium hypochlorite or
calcium hypochlorite
which yield hypochlorous acid and
atomic oxygen
 Oxidised cellular material destruct vegetative
bacteria and fungi ,not spores

42. Quaternary ammonium
compound
 Detergents
organic molecules that serves as a
wetting agents and emulsifiers because
they have both polar hydrophilic and
nonpolar hydrophilic ends.
 Due to their amphipathic nature detergent
solubilise insoluble residues and are
very effective cleansing agents.
 Disrupt microbial membrane ,may also denature
proteins

43. Heavy metals
 Ions or heavy metals such as Hg ,Ag ,arsenic
,zinc ,Cu used as a germicides
 1 % of solution of silver nitrate is added to eyes of
infants to prevent ophthalmic
gonorrhea
 Silver sulfadiazine is used on burns
 Copper sulphate is an effective algicide in lakes
and swimming pools.
 Act by combining with proteins often with their
sulfhydril groups inactivate them or precipitate cell
protiens.

44. Laboratory using sterilization
techniques
 Dry heat
 Flame sterilisation
 autoclaving

45. Thank you