DISINFECTANTS AND STERLANTS
Disinfectant is a germicidal, chemical substance that kills microorganisms
on inanimate objects, such as instruments and other equipment, that cannot
be exposed to heat. Disinfectants differ in their spectrum of activity.
They do not kill the tubercle bacillus or spores.
Antiseptic is a chemical agent that either kills pathogenic microorganisms
or inhibits their growth as long as there is contact between agent and
microbe. By custom as well as federal law, the term "antiseptic" is
reserved for agents applied to the body.
Sterilization is the process of killing all microorganisms including all
bacteria, fungi, viruses, and spores with the use of either chemical or
The following agents are commonly used as disinfectants, and
antiseptics, and sterilants.
Glutaraldehyde: 2% glutaraldehyde solution are used for cold sterilization.
They are commercially available as Cidex (Surgikos-Johnson & Johnson) and
Sporicidin (Ash-Dentsply). These agents are diluted with an activator prior
to use and have limited shelf lives after dilution (14 days for Cidex; 30
days for Sporicidin). they can be used for disinfection or sterilization
depending upon the time allowed for instrument contact. Cidex and
Sporicidin require 10 hours of contact time for sterilization. Instruments
may be soaked for 10 minutes in Cidex solution, to remove vegetative
bacteria, when performing surgical procedures on multiple animals as long
as they are sterilized throughly before the first procedure in the
sequence. Glutaraldehyde is toxic to skin and mucous membranes. It must be
rinsed from instruments and other items with sterile water before use. It
is the "cold" sterilant of choice for lensed instruments.
Chlorine Compounds: Household Bleach (5% sodium hypochlorite) is effective
against all classes of microorganisms but is inactivated by organic debris.
It can be used as a disinfectant on previously cleaned surfaces at a
dilution of 1:20. Full strength or a 1:5 dilution is recommended against
hepatitis B virus, HIV or on surfaces soiled by potentially contaminated
fluids. Some authors claim that the tubercle bacillus and other similar
organisms are resistant to hypochlorite. it must be made fresh; solutions
that are allowed to sit may deteriorate. Bleach will damage fabric and is
an irritant to mucous membranes. Chlorine dioxide (Clidox or Alcide), is
available as a binary system, consisting of a base and an activator, which
require mixing. Once prepared the usable life of the solution is 14 days.
Chlorine dioxide is effective against all classes of microorganisms
including bacterial spores. Three minutes of contact time is necessary for
Alcohols: Alcohols destroy bacteria via the coagulation of protein. They
have poor activity against bacterial and fungal spores, evaporate rapidly
if kept in open containers, form flammable mixtures with air, are
inactivated by organic matter, and dissolved lens cement mountings. In
spite of these shortcomings, they are rapidly bacteriocidal and are useful
antiseptics. Isopropyl alcohol is typically used as a 70% solution; ethyl
alcohol is used between 75 and 90%. Ethyl alcohol has abuse potential and
must be kept in locked cabinets. When used as antiseptics, they are
disinfectants as long as they remain in solution. As such they may be used
for emergency disinfection of instruments by immersion for 20 minutes.
Povidone-Iodine: Free iodine is complexed to the polymer povidone to
produce a non-toxic antiseptic. Povidone-iodine is effective against all
classes of microorganisms. It is most commonly used as a surgical scrub
(Betadine Scrub, Purdue-Frederick) at 7.5%. It is also available as a 10%
solution (Betadine Solution); the solution is used undiluted to paint the
skin after an appropriate surgical scrub.
Chlorhexidine acetate: Chlorhexidine acetate is commercially available as
both a 2% solution and 2% surgical scrub (Nolvasan Solution; Nolvasan
Surgical Scrub, Aveco/Fort Dodge). The scrub is used undiluted as a
antiseptic. The solutions used as a disinfectant by diluting 3 ounces to a
gallon of water. Nolvasan solution is not effective against gram + cocci or
pseudomonas aeruginosa on inanimate objects.
Chlorhxidine is neutralized by alcohols, therefore the two agents should
not be used in combination.
Quaternary ammonium compounds (Benzalkonium chloride): The two products
included in this group of agents are Roccal D (Winthrop) and Zephiran
(Winthrop). Roccal D is used to decontaminate surface (i.e it is not used
on instruments). A 1:200 dilution with water is recommended by the
manufacturer. It is effective against a variety of viruses, gram + and gram
- bacteria. Zephiran has been largely supplanted as an antiseptic by
Betadine. When Zephiran is used, it is used as a "tincture" (i.e with
alcohol at a dilution of 1:750). Zephiran may be used to disinfect
instruments between animals (20 minute soak) when surgical procedures are
performed on multiple animals during a session. These agents have no effect
against the tubercle bacillus and are inactivated soaps.
Ethylene oxide: Ethylene oxide is a cyclic ether with bacteriocidal,
sporicidal and fungicidal properties. It is used in its gaseous state and
is marketed in ampules under the trade name Anprolene (Andersen Products).
Partial pressure of the agent is important for microbiocidal effect,
Ethylene oxide can be used to sterilize heat sensitive plastics and lensed
instruments. Items must be exposed to ethylene oxide for 12 hours and then
aerated. Aeration times range from several hours to weeks depending upon
whether passive or mechanical aeration is used. Aeration is required
because ethylene oxide is a skin and mucous membrane irritant. Ethylene
oxide sterilization and aeration should be done under a fume hood; gloves
should be worn when breaking the ethylene oxide ampule or when handling
ethylene oxide sterilized items prior to aeration. Alkylation of nucleic
acids is considered the mechanism of action. Objects sterilized by
radiation should not be resterilized with ethylene oxide (toxins are
produced that are difficult to elute).
Click here to Appendix I