TUTORIAL : DISINFECTANTS/STERILISING
Objectives:
At the end of this tutorial you will be able to:
1.
List and discuss the importance of factors affecting the results of
disinfection.
2.
Define and give examples of Critical, Semi-critical Non-critical equipment.
3.
Know what factors are to be considered when selecting a particular
disinfectant or antiseptic.
4.
Define the suffixes –cidal and –static as it relates to disinfection know
which type of product is more desirable.
5.
Know which general classes of disinfectants are most effective against
bacterial spores, viruses and fungi – give an example of a disinfectant
product for each class.
Control or Elimination of Infectious Agents
Cleansing, Antiseptics, Disinfectants and Sterilisation
The effective use of antiseptics, disinfectants and sterilisation procedures is an
important factor in preventing nosocomial infections. Although used on a daily
basis, often with some interchange, the exact distinction among the three terms is
extremely important if effective application is to be realised.
Sterilisation: is defined as the use of physical or chemical procedures to destroy all
microbial life, including highly resistant bacterial spores. Will be discussed in
detail in Surgical nursing module.
Disinfection: Destroys disease producing microorganisms or inactivates viruses
(but not usually bacterial spores) on inanimate objects eg patient-care equipment,
walls, cages, tables, floors, walls. Disinfectants include chemical agents and some
physical processes eg boiling.
Antiseptic: is defined as a substance that is used on living tissue for the purpose of
inhibiting or destroying microorganisms, without damaging the animal’s cells.
Skin Disinfectants: are antiseptic preparations designed either for pre-operative
skin cleansing or for use with inanimate objects.
Environmental Disinfectants: are designed for use on inanimate objects only;
many of them require the user to wear protective clothing and they should never be
used on skin.
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Factors affecting the results of disinfection include:
1.
Concentration of solution and duration of contact with the chemical. A
weakened concentration or shortened exposure time may lessen
effectiveness.
2.
Amount of organic matter (soil, blood, faeces, pus, saliva, urine) present.
Disinfectants can become inactivated unless organic matter is washed off
first.
3.
Surface areas to be disinfected eg porosity, cracks etc. Also, all dirty
surfaces and areas must be fully exposed to disinfecting agents.
4.
The material to be disinfected.
5.
Ambient temperature. Disinfectants tend to work best at room
temperature.
6.
Presence of soap. Soap may cause certain disinfectants to be ineffective.
Thorough rinsing of an object is necessary before disinfecting.
7.
Nature and number of the contaminating microorganisms. Certain are
killed more easily than others by disruption. The greater the number of
pathogens on an object the longer the required disinfecting time.
When selecting germicidal procedures, patient-care equipment can be classified as
critical, semi-critical and non-critical.
Critical: equipment includes those devices that are introduced directly into the
body, such as surgical instruments, catheter and implants. Sterility is essential.
Semi-Critical: equipment includes those items that come in contact with various
mucous membranes. Although sterilisation is desirable, it is not essential.
Disinfection of these items should inactivate vegetative bacterial cells and viruses.
Examples of semi-critical equipment includes thermometers, speculums,
endotracheal tubes, and otoscope heads, clipper blades and other diagnostic
equipment eg endoscope, arthroscope etc.
Non-critical: equipment includes environmental surfaces, such as cages, tables,
floors, walks etc. These surfaces should be cleaned with detergent, rinsed well
and chemically disinfected.
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Selecting Disinfectants and Antiseptics
See table of commonly used disinfectants and antiseptics for main active
ingredients and recommended uses. Detailed information regarding each
product’s suitability in veterinary practice can be obtained by reading the
manufacturer’s data sheets. Some of the main factors to consider when selecting a
particular product include:
1.
The intended use
environmental eg kennels, cages, stalls, runs, equipment
on living tissue eg skin, wounds
2.
The product’s activity against specific microorganisms.
3.
The contact time required.
4.
Known local conditions eg water hardness.
5.
Safety to animals and people.
A product should be non-irritant, non-toxic and non-corrosive. Consult the
manufacturers product details for recommended safety precautions eg
protective clothing, ventilation. Some animal species are sensitive to some
types of disinfectant (eg cats are sensitive to phenol; and formalin vapour
irritates many animal’s eyes.)
6.
Stability in storage
7.
Odour. Preferably odourless or have a pleasant aroma. Strong odours or
perfumes are offensive to some animals, promoting sneezing and irritation
to the eyes.
8.
Ease of use, eg should disperse readily in water if dilution is required.
9.
Economy of use, eg cost per litre of diluted solution.
10.
Effectiveness in the presence of organic matter. The presence of even
relatively small amounts of organic material in water may render some
disinfectants ineffective eg Savlon, Bleach.
Effectiveness of Disinfectants against different microorganism
Bacteria:
The bactericidal capability of a disinfectant varies as some forms of bacteria are
more resistant than others.
The following list is in descending order of resistance of bacteria to disinfection:
Bacterial spores (most resistant)
Acid fast Bacteria eg Mycobacteria spp., Yersinia spp.
Gram Negative Bacteria eg E.coli, Salmonella spp., Klebsiella spp.
Gram Positive Bacteria eg Staphylococcus spp., Streptococcus spp.
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Disinfectants most effective against bacterial spores include:
Aldehydes
Ethylene Oxide
Halogens (lesser extent)
Disinfectants most effective against viruses include:
Hypochlorites (eg Bleach)
Glutaraldehyde (but slow acting)
Ampholytic surfactants kill some viruses
Many disinfectants are able to destroy fungal spores. Quaternary ammonium
compounds and Pine oil fluid DO NOT KILL FUNGI!
-cide (cidal)
Indicates a product/chemical that kills particular type of
microorganism eg, bacteriacide – kills bacteria; fungicide – kills
fungi
-stat (static)
Indicates a product/chemical that prevents or inhibits the growth of
a particular type of microorganism. It is best to choose a disinfectant that kills a
microorganism rather then inhibits it’s growth.
Chemical Disinfectants and Antiseptics
Product Name
Active
Ingredients
Presentation
Uses/Comments
Isopropyl alcohol
Ethyl alcohol
Methylated spirits
Alcohol
liquid
Ethyl alcohol more
effective than Isopropyl
or Methyl for
disinfection. General
surface and skin
disinfection. Moderately
virucidal only in high
concentration.
Bleach
(Halogen)
hypochlorites
Liquid
Bactericidal and
Virucidal; Highly
effective, rapid acting but
organic matters interferes,
inexpensive, non-toxic.
Environmental
disinfectant, Do not
splash on clothes.
Cetavlon
(Quaternary
ammonium
compound)
Cetrimide
Liquid
Environmental use and
skin disinfectant. Not
very effective against
many viruses; organic
matter interferes.
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Halamid
(Halogen)
Sodium
tosychloramide
Powder
Environmental use and
skin, pre-injection, udder,
hands.
Jeyes Fluid
(Phenol)
Phenol
compound
Liquid
Environment use ONLY;
Rinse thoroughly; NOT
FOR CAT HOUSING.
Dettol
(Phenol)
Chloroxylenol
Liquid
Envrionmental use and
skin disinfection. NOT
FOR CAT HOUSING.
Formula H
Formaldehyde
Liquid or
Spray
Environmental use only.
Low power of
penetration. Use for
terminal disinfection;
irrititating;
hypersensitivity may
result.
Marinol Blue
Roccal
Benzalkonium
Chloride
Solution
10% or 50% Sol’n Pre-op
instruments. Topically
(skin diluted.)
Parvocide
(Glutaraldehyde
Q.A.C)
Aldehyde
Liquid
Broad spectrum
disinfection for all
animal contact surfaces.
Environmental only.
Detergent
Iodophors
Betadine
Liquid
Action based on slow
release of iodine and
detergent action. Less
affected by organic matter
than bleach. Stains some
surfaces. Expensive.
Environmental and skin
disinfection.
Vet-cide
Tri-n-butyltinbenzoate
Liquid
Environmental use only.
Powder
Environmental use only.
Formaldehyde
Isopropyl alcohol
Virkon
(Perioxide)
Oxidising agents
Hibicet
Cetrimide
Liquid
Chlorhexidine
gluconate
Isopropyl alcohol
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Environmental and skin
disinfectant.
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Trigene
halogenated tertiary
Amine, biguanide
liquid
and spray
Hydrochloride
Benzyl ammonium chloride
Dodecylamine sulphate
general purpose food prep
and high level
disinfection of surfaces
Common Antiseptics
Product
Name
Active
Ingredient
Presentation Uses/Comments
Hibiscrub vet
Chlorhexidine
gluconate
Solution
Rapid bactericidal skin
cleanser and surgical
scrub. Ototoxic and
corneal irritant
Nolvasan Surgical
Chlorhexidine
Acetate
Solution
Skin and wound cleanser.
Ototoxic and corneal
irritant
Povidine
Antiseptic
Solution
Povidine-iodine
Solution
Topical application
Burns/Wounds etc
Savlon Vet
Concentrate
Chlorhexidine
gluconate
Cetrimide
Solution
Wounds(dilute); pre-op
Precautions and use of Chemical Disinfectants
When using any chemical, including disinfectants and cleaning materials, care
should be taken to ensure their correct handling:
-
Store in the original containers with the lids secured
Keep away from animals and children
Wear protective clothing when recommended; always avoid
contact with the skin
ONLY use disinfectants for the purpose recommended by the
manufacturer
Use the correct concentration for the surface to be disinfected
Wash hands thoroughly after use, especially eating or drinking.
Some general rules apply to the use of disinfectants:
-
Use the correct dilution. Too weak = ineffective; Too strong =
wasteful but also can lead to irritation of animal skin, eyes, feet,
respiration. Inadequate rinsing can cause similar problems.
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-
Use water only to dilute disinfectants. It is potentially dangerous
to mix disinfectants (noxious gases or corrosive action) unless
recommended by the manufacturer.
-
Use at the chemical’s optimum temperature for action. Many
disinfectants are more effective when used with hot water than
with cold. With others this is not an issue.
-
Ensure appropriate contact time is allowed. All disinfectants
require TIME to kill or inactivate microorganisms and are
ineffective if rinsed off too soon after application. Contact time
will vary with the type of disinfectant and the organism to be
killed. Consult manufacturers instructions.
-
USE FRESHLY MADE UP SOLUTIONS. Many disinfectants
begin to deteriorate when mixed with water.
-
Equipment and receptacles used with disinfectants should be
thoroughly clean and rinsed before use. Organic matter reduces or
inactivates many disinfectants.
-
All disinfectants should be thoroughly rinsed off once the contact
time is completed, unless otherwise recommended.
-
Always adhere to precautions recommended by the manufacturer.
Commonly used disinfectants
1. Virkon (sodium peroxomonosulphate, sodium dodecylbenzene sulphonate,
sulfamic acid): mix at 1:50 dilution for activity against parvovirus and
1:100 against other micro-organisms ie. Bacteria, fungi, mycoplasmas and
moulds. This is a one-step disinfectant for all surfaces and equipment.
2. Sodium hypochlorite (Bleach). 0.175% will kill viruses as well as bacteria
and fungi(ringworm) the activity is inhibited by the presence of organic
material so thorough cleaning is importat and even then bleach is often
used at double strength 0.25%. Ensure the stronger concentration is used
for cleaning after parvovirus cases.
3. Spray–n-wipe /Exit mould (sodium hypochlorite) are other commercial
cleaners that can be used for bench tops routinely. For infectious cases,
Virkon can be used safely afterwards.
4. Savlon can be used for the environment and skin disinfection. Diluted 1:20.
Not so effective for fungi, so inadequate if ringworm is suspected
5. Dettol can be used for skin and the environment. But because of the danger
of cat respiratory reactions not commonly used in veterinary situations
6. Trigene for general disinfection of unsoiled surfaces, dilute Trigene Advance
1:200. In the presence of organic matter , after cleaning use 1:100 dilution.
Rinse and dry before use
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DISINFECTANT AND ANTISEPTIC TUTORIAL
1. Examine the products commonly available in veterinary clinics. For
those products complete the chart:
Active
Recommended
contraindications
ingredient
use
Virkon
Trigene
Hibicet
Bleach
Dettol
Biocil
scrub(detergent
iodophor)
2. Show the calculations to make up:
300mL of 1% Virkon (Virkon is supplied as a powder)
5 litres of 0.25% bleach. (Janola is supplied as 42g/L)
3. Which products are suitable for disinfecting plastic otoscope cones
and clipper blades to ensure there is no transmission of fungi/yeast
infection. (What strength?)
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4. Which product can be used for disinfecting the stones in aquariums?
5. Which products can be used in the presence of organic matter?
Which cannot?
Trigene
Virkon
Janola
Povidine iodine
Hibiclens
6. Which products have residual activity?
Trigene
Virkon
Janola
Povidine iodine
Hibiclens
7. which may be used as antiseptics?
Trigene
Virkon
Janola
Povidine iodine
Hibiclens
8. When should a solution of Virkon be changed?
9. When should a solution of Hibitane used to disinfect thermometers
be changed
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