Matching the Right Disinfectant to the Job
By Michelle Gardner
Antimicrobials are substances used to destroy or suppress the growth of
microorganisms, such as bacteria, viruses, or fungi, and are used to control
infectious microorganisms on surfaces. The more commonly used antimicrobial
products are sterilants, disinfectants, and sanitizers.1
It is not necessary to sterilize all patient-care items, so hospital policies
must identify whether disinfection or sterilization is indicated on the basis of
each item's intended use.2 The purpose of the revised Association for
Professionals in Infection Control and Epidemiology (APIC) guideline is to
assist healthcare professionals in their decisions involving the judicious
selection and proper use of disinfectants. (See www.apic.org)
The Centers for Disease Control and Prevention (CDC) defines the three levels
of disinfection in its "Guidelines for the Prevention of Transmission of
Human Immunodeficiency Virus and Hepatitis B Virus to Healthcare and
Public-Safety Workers." High-level disinfection can be expected to
destroy all microorganisms, with the exception of high numbers of bacterial
spores. Intermediate-level disinfection inactivates Mycobacterium
tuberculosis, vegetative bacteria, most viruses, and most fungi, but it does
not necessarily kill bacterial spores. Low-level disinfection can kill
most bacteria, some viruses, and some fungi, but it cannot be relied on to kill
resistant microorganisms such as tubercle bacilli or bacterial spores.
"There is a direct correlation between that level of disinfection and
any given patient-care item upon which you use it," says Robert Sharbaugh,
PhD, a consultant for ICP Associates in Charleston, S.C. "Not only do you
have low, intermediate, and high levels of disinfectants, but you have
non-critical, semi-critical, and critical categories of patient-care items.
Critical items go into any sterile area of the body, including the blood
vascular system. They have to be sterile. Semi-critical items will not go into a
sterile area of the body, but they will come in contact with either non-intact
skin or mucous membranes. Non-critical items only come into contact with intact
skin, no mucous membrane contact, no sterile-body contact, and no denuded skin
By definition, an intermediate-level disinfectant is one that will inactivate
Mycobacterium tuberculosis and/or HIV and HBV. "If one wants to be
in compliance with the bloodborne pathogen standard that OSHA promulgates, then
the wise and most cost effective thing to do is to get a US Environmental
Protection Agency (EPA)-registered tuberculocidal agent and use it throughout
the hospital," says Sharbaugh. "The EPA has a web site (www.epa.gov/oppad001/chemregindex.htm)
listing all EPA-registered tuberculocides and disinfectants that are effective
against HIV and HBV."
It is difficult to determine the number of hospital-acquired infections that
may be prevented by use of registered disinfectants. However, there is a great
deal known about infectious microorganisms, how they spread disease, and what
can be done to halt the spread of infections. For example, it is believed the
most important factor in preventing the spread of diseases in hospitals is
related to how often and how thoroughly HCWs wash their hands. Disinfectants and
other factors may also play important roles. EPA-registered sterilants and
disinfectants used in healthcare facilities are presumed to play a vital role in
reducing transmission of harmful microorganisms from surfaces to people.1
A number of disinfectants are used in hospitals, including: alcohol, chlorine
and chlorine compounds, formaldehyde, glutaraldehyde, hydrogen peroxide,
iodophors, phenolics, and quaternary ammonium compounds. These disinfectants are
not interchangeable.2 The proper selection and use of disinfectants
is essential for safety and quality control. Disinfectants have various
characteristics that must be considered before one is selected for a particular
Alcohols demonstrate variable effectiveness against some bacterial and
fungal species. They are good general-use disinfectants that are fast acting,
leave no residue, and compatibly combine with other disinfectants (quaternaries,
phenolics, and iodine) to form tinctures.
Aldehydes are effective against a wide spectrum of bacteria and
viruses, are sporicidal when used properly (10-hour contact period), and
demonstrate activity against vegetative bacteria, spores, and viruses.
Activated Glutaraldehyde requires limited and controlled use because
of its toxic properties. It must only be used while wearing a ventilated hood.
It has limited stability after activation (for alkaline glutaraldehyde).
Chlorine compounds are good disinfectants for the clean-up of blood or
body-fluid spills. They have a biocidal effect on M. tuberculosis, S.
aureus, other vegetative bacteria, and HIV after 10-20 minutes, 1:5 dilution
(250 ppm) for bacterial spores and mycobacteria. Diluted chlorine bleach stored
at room temperature in a closed plastic container will deteriorate by one half
after one month, neutralizes rapidly in the presence of organic matter, is good
for decontamination of HBV, HCV, HIV, and the clean-up of biohazardous spills.
Undiluted bleach is good for surface disinfecting after possible contamination
with the CJD virus; however NIH recommends 1.0 N NaOH.
Iodophor is effective against vegetative bacteria and viruses. It
demonstrates poor activity against bacterial spores, however it has a rapid
biocidal action. It is effective against Gram-negative and Gram-positive
organisms, some viruses, and tubercle bacilli, and is most effective in acid
solutions. It can vaporize at 120º F to 125º F (should not be used in hot
water), and its effectiveness can be reduced by organic matter. It is stable in
storage if kept cool and tightly covered. It is still active if the solution is
brown or yellow.
Mercurials demonstrate poor activity against vegetative bacteria and
are not effective on spores. They are toxic and not recommended for use.
Phenolic compounds are effective against vegetative bacteria, fungi,
and lipid-containing viruses. They have low solubility in water, are stable in
storage, are germicidal against Gram-negative and Gram-positive organisms and
tubercle bacilli, are effective over a large pH range, and have limited
sporicidal activity. Prolonged contact deteriorates rubber, and can cause skin
and eye irritation. Not for use on food-contact surfaces.
Quaternary ammonium compounds are acceptable to control vegetative
bacteria and non-lipid-containing viruses. They are stable in storage, have no
odor but act as deodorizers. They are non-irritating to skin but skin or eye
contact should be avoided. They are effective at temperatures up to 212º F, are
effective against Gram-positive organisms, are bacteriostatic in high dilutions,
are ineffective against tubercle bacilli, spores, and viruses, are more
effective in alkaline than acid solutions, are neutralized by soap, and their
effectiveness is reduced by organic material.