chemical disinfection

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DISINFECTION
by
Chemical Approach
DEEPAK CHAUDHARY
Senior Demonstrator
GMC AMBIKAPUR

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5. ANTISEPTICS VERSUS DISINFECTANTS
Antiseptics:
 Use on skin and mucous membranes to kill
microorganisms
 Not for use on inanimate objects
Disinfectants:
 Use to kill microorganisms on inanimate
objects
 Not for use on skin or mucous membranes
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6.  It should have a wide spectrum of activity and should be
effective against all microorganisms.
 It should posess high penetrating power.
 It should not corrode metals during sterlisation of
instruments.
 It should not cause irritation or sensitisation when
applied on body.
 It should not be toxic in case it is absorbed into
circulation.
 It should be active even in the presence of organic
matter, effective in acid/alkaline medium, should be
stable, compatible with other disinfectants/antiseptics
and inexpensive.
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7.  Concentration of the substance.
 Time of action
 pH of the medium.
 Temperature
 Nature of the organism
 Presence of organic matter.
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8.  By protein coagulation.
 By disruption of the cell membrane resulting in
exposure, damage or loss of contents.
 By removal of free sulphydryl groups essential
for the functioning of enzymes.
 By substrate competion- a compound
resembling the essential substrate of the
enzyme diverts or misleads the enzymes
necessary for the metabolism of the cell and
causes death.
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 A chemical that kills all microbial pathogens
except large number of spores but may have
some activity against a smaller number of spores
if contact time is increased.
 These include GLUTERALDEHYDE, HYDROGEN
PEROXIDE, PERACETIC ACID, CHLORINE DIOXIDE
AND OTHER CHLORINE COMPOUNDS.
Intermediate level disinfectants
 A chemical that kills all microbial pathogens
including mycobacteria and non enveloped
viruses except spores.
 These disinfectants include ALCOHOLS,
IODOPHORE COMPOUNDS AND PHENOLIC
COMPOUNDS.
LOW LEVEL DISINFECTANTS:

11.  Most frequently used alcohols are Ethyl alcohol (ethanol),
methyl alcohol (methanol) and isopropyl alcohol
(isopropanol).
 These are mainly used as skin antiseptics and act by
denaturing bacterial proteins.
 Antimicrobial activity of alcohol is enhanced by water with
optimal conc. Being 70-90%.
 Isopropyl alcohol is preferred as it is a better fat solvent
more bactericidal and less volatile. It is used for the
disinfection of thermometers.
 Methyl alcohol is effective against fungal spores. Used for
disinfecting cabinets and incubators affected by the
fungal spores.
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12.  1. GLUTERALDEHYDE
 Broad spectrum disinfectant active against bacteria
(specially tubercle bacilli), viruses and fungi. It is available
commercially as cidex.
Uses
 Often used for sterlisation of cystoscopes, endoscopes,
bronchoscopes that cannot be sterlised or disinfected by
heat.
 Used to sterlise corrugated rubber anaesthetic tubes,
plastic endotracheal tubes, face mask, metal instruments
and polythene tubing.
 Precaution: it is an irritant to the eyes, skin and respiratory
mucosa, so must be handled with care and adequate
ventilation facility.
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13.  2. FORMALDEHYDE
 Formaldehyde is used as a disinfectant and sterilant both
in the liquid and gaseous states. Formaldehyde is sold
and used principally as a water-based solution called
formalin, which is 37% formaldehyde by weight.
 It is used both as aqueous and gaseous form.
 The aqueous solution is bactericidal, tuberculocidal,
fungicidal, virucidal and sporicidal.
 Used to destroy anthrax spores in hair and wool, footwear
of person with fungal infection, to fumigate wards and
operation theatres, disinfection of heat sensitive
equipment and to preserve anatomical specimen.
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14.  3. BETAPROPRIOLACTONE
 It is a condensation product of ketane and formaldehyde.
 It was earlier used for fumigation but is no longer used as
it has carcinogenic activity.
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15.  Lister, the father of anti-septic surgery first introduced the
use of phenol in surgery.
 It is obtained from distillation of coal tar between
temperatures of 170 – 270 degrees.
 Certain phenol derivatives are used as antiseptics.
 Cresols - lysol is a solution of cresol in soap. It is most
commonly used for sterlisation of infected glasswares,
cleaning floors, disinfection of excreta.
 Chloroxylenol – active ingredient of dettol.
 Chlorohexidine – savlon (chlorohexidine and cetrimide) is
widely used in burns, wounds and preoperative disinfection of
skin.
 Hexachlorophane – applied on skin as prophylaxis against
staphylococcal infection. Bacteriostatic at high dilutions.
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 CHLORINE and IODINE are commonly used.
 Chlorine compounds are used as disinfectants in water
supplies, swimming pools and food and dairy industries.
 Chlorine is most commonly used as sodium hypochlorite.
 Chlorine in hypochlorites reacts with water to form
hypochlorous acid which is a strong oxidising agent and
effective disinfectant.
 Sodium hypochlorite 5.25% is called household bleach.
 Iodine is actively bactericidal with morderate action
against spores.
 Compounds of iodine with surface active agents is known
iodophores which are more active than iodine.

17.  Hydrogen peroxide
 Effective against most organisms at conc of 3-6% and against
spores at 10-25% .
 On decomposition H2O2 liberates free hydroxyl radical which are
active ingredient in disinfection
 Used to disinfect plastic implants, contact lenses and surgical
prostheses.
 Peracetic acid
it is an oxidising agent and high level disinfectant. Used in plasma
sterlisation.
 Plasma sterlisation
Commercially available plasma sterlisers are sterrad 100s and
plazlyte sterliser.
 Hydrogen peroxide and peracetic acid is used in these devices to
induce the plasma. Resulting UV radiation causes destruction of
vegetative organisms and spores.
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18.  Salts of heavy metals like copper, silver and mercury have toxic
effect on bacteria.
 These are protein coagulants and combine with sulphydryl groups of
bacterial proteins.
 Eg mercuric chloride and silver nitrate.
VII. SURFACE ACTIVE AGENTS
 Substances that alter energy relationship at interfaces, producing a
reduction of surface tension are known as surface active agents or
surfactants.
 Classified into four groups- anionic, cationic, nonionic and
amphoteric.
 Act on the phosphate group of cell membrane and denature cell
proteins.
 Eg acetyl trimethyl ammonium bromide and benzalkonium chloride.
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19.  Two groups of dyes, aniline and acridine are used as skin
and wound aniseptics.
 Aniline dyes in use are brilliant green, malachite green
and crystal voilet. These are more active against gram
positive organisms. These are used as selective agents in
culture media. (LJ media)
 Acridine dyes are proflavine, acriflavine, euflavine and
aminacrine. These are used in clinical medicine. They
impair the DNA complexes of the organism.
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VIII. DYES

20.  FORMALDEHYDE GAS
 Employed for fumigation of operation theatres, wards and labs.
 Gas is generated by adding 150 g of KMnO4 to 280 ml of formalin
for every 1000 cu. Feet of room volume.
 Sterlisation is achieved by condensation of gas on exposed
surfaces.
 EHTYLENE OXIDE
 Colorless liquid with a boiling point of 10.7 degrees.
 It acts by alkylating the amino, carboxyl, hydroxyl and sulphydryl
groups in protein molecules.
 It is highly inflammable, mutagenic and carcinogenic.
 It is a highly penetrating gas and is used to sterlise plastic and
rubber articles, respirators, heart lung machines, sutures, dental
equipments and clothing.
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21.  Critical items
 These are those which enter sterile tissue or
vascular system and pose high risk of infection.
It includes surgical instruments, cardiac
catheters, implants etc
 They must be sterlised by autoclaving if heat
stable.
 If heat sensitive then sterilization should be
done by ethylene oxide or hydrogen peroxide
gas plasma.
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22.  Semi critical items
 Articles which come in contact with mucous
membranes or non intact skin are called semi
critical items and require high level disinfection.
 Gluteraldehyde is most commonly used high
level disinfectant.
 Endoscopes and bronchoscopes,thermometers
are some examples.
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23.  These items come in contact with intact skin
but not mucous membranes. For eg bedpans,
blood pressure cuffs, bed rails, bedside tables
etc.
 They can be treated with low level disinfectants.
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