1. Sterilization
no degree (relativity) of sterility
sterile or non-sterile
Physical
methods
Chemical
methods
Mechanical
methods
Moist (steam) heat
Dry heat
by radiations
by Autoclave at 121º C for 20 : 30 minutes
steam∝Temp.∝pressure∝1/minimum sterilization time
Adv
High penetration power of steam more efficiently
In large size autoclaves large quantities
App
Disadv
Not for thermo and moisture sensetive as
oils, fats, ointments,powders, oily injections
by oven (hot air sterilized by HEPA filters)
Adv
Disadv
App
Adv
Disadv App
at 160 ͦ
C for at least 2 hrs
the method of choice for sterilization of glassware (Tunnels) to kill spores
For thermo stable and moisture sensetive as oil & dry powder
due to physical characters
Requires very long heating times & high temp
Not for
thermolabile drugs, rubber and plastic articles
preparations containing water, alcohol or volatile substances
surgical dressing due to quickly vaporization
of fibres moisture causing charring
powders must be spread in thin layers due to weak penetration
Greater thermal capacity of steam
In presence of moisture, denaturation or
coagulation of essential proteins present in
microorganisms takes place at lower
temperature and lesser time
Maintenance of positive pressure to prevent nonsterile
air entry (P out < P in)
Moist Heat with
Bactericide
bactericide is added to solution in final containers
sealed containers heated at 100 ͦ
C for 30 min in a steam sterilizer
killing is done by heat and bactericide
Disadv
Not for intravenous injections when a single dose
of the solution is more than 15 ml
cold sterilization as no heat is used
for heat and moisture sensitive materials
Ultra Violet
(UV) Light
Sources
Natural
artificial
sunlight (quite harmful to M.O.)
UV lamb
very weak penetration power
effective only to the exposed surface
reduce airborne contamination
sterilization of a septic rooms or areas
harmful to the skin and eyes
organs must be properly protected
Gamma Rays
(Ionic radiation)
from radioactive isotopes of cobalt 60
kill m.o. by ionization of atoms of essential components
of M.O.
Adv
high penetration power.
For
parenteral containing antibiotics,vitamins(ascorbic acid)
bacterial and viral vaccines
influenza
poliomyelitis
rabies
Quite reliable
method due to
short exposure time
large quantities can be sterilized at once
Disadv
High cost
harmful to personnel so they must be protected
change in color,solubility,texture & decomposition of drugs
Gaseous
by disinfectants
a special type of chemical sterilization
EX: chlorine, ozone,formaldehyde and ethylene oxide.
Ethylene
Oxide
Only when no other method is practicable
a colorless gas at ordinary temperature
kill m.o. by alkylating the essential substances in protein
its odor is similar to ether
cause inhalation toxicity similar to
ammonia dioxide
fluorinated hydrocarbons
FREON
Label
"ETO" or "STERILE EO"
Adv
great penetrating power.
for thermolabile and moisture sensitive
Disadv
Highly inflammable
requires special precautions
Costly equipment
Residual gas may present
Formaldehyde
for fumigating the out of control sterile areas
effective bactericidal agent
kills all bacteria including spores
Disadv
Adv
App
Difficulty to expel the gas from sterilizing area
Stop production for 3 days
by filtration
solution are passed through bacteria proof filters
bacteria are entrapped in the pores of the filters
Adv
for thermolabile and moisture sensitive
Disadv
very slow process, vacuum and/or
pressure to enhance filtration
so large quantities can be sterilized at short time
Considerations
Filtration with some form of heat treatment
Double filtration
Filters should not shed particles
e.g. Asbestos filters.
Same filters should not be used for more
than 1 day unless validated
Not for glass wares as they discolor and darken in color.
preferred for ampoules, vials, syringes,needles
Equipment or devices made up of metal
Rubber articles as stoppers, gloves&
surgical needles&instrunments
Rubber as high temperature will spoil the rubber articles
Aqueous solutions of thermostable
Glassware, vials or ampoules of solutions,
Solid thermostable chemicals (powder)
Dressings impregnated with soft paraffin
Clothes&surgical dressings made of cotton cellulose
Apps
Solid thermostable chemicals (powder)
Dry Heat
Aqueous solutions of thermolabile
Double filtration under aseptic conditions
Not by
steam heat with a bactericide
steam heat
Aqueous solutions of thermolabile(vitamin)
Ex
Most ophthalmic alkaloid solutions
antibiotic solutions
vitamins injections as ascorbic acid
Aqueous solutions of thermostable
Moist Heat
Intravenous solutions (dextrose,electrolytes,
irrigating solution) & all thermostable injections
in ampoules or vials
filtration under aseptic
conditions then moist heat
Non sterile container
sterile container as no terminal sterilization
Moist Heat surgical dressings of cotton or cellulose
Dry Heat surgical dressings of soft parrafin
sterilization failure
due to non contact between sterilizing
agent and processed items
sterilization time
variations depend on
load, arrangement, packaging material, temperature
sterilizing agent type
High penetration power
Moist (steam) Heat
Gamma (ionic) Radiation
Ethylene Oxide (ETO)
