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Antibacterial agents
What
is an antibacterial and how are antibacterials classified?
In its broadest
definition, an antibacterial is an agent that interferes with
the growth and reproduction of bacteria. While antibiotics and
antibacterials both attack bacteria, these terms have evolved
over the years to mean two different things. Antibacterials are
now most commonly described as agents used to disinfect surfaces
and eliminate potentially harmful bacteria. Unlike antibiotics,
they are not used as medicines for humans or animals, but are
found in products such as soaps, detergents, health and skincare
products and household cleaners.
What
are some common antibacterials?
Antibacterials
may be divided into two groups according to their speed of action
and residue production: The first group contains those that act
rapidly to destroy bacteria, but quickly disappear (by evaporation
or breakdown) and leave no active residue behind (referred to
as non-residue-producing). Examples of this type are the
alcohols, chlorine, peroxides, and aldehydes. The second group
consists mostly of newer compounds that leave long-acting residues
on the surface to be disinfected and thus have a prolonged action
(referred to as residue-producing). Common examples of
this group are triclosan, triclocarban, and benzalkonium chloride.
See the Table
of Antibacterials.
How
common are antibacterials in consumer products?
All products
that claim to kill bacteria and/or viruses have some kind of antibacterial
agent. Alcohols, chlorine and peroxides have been used for many
decades in health-care and cleaning products. Within the past
two decades, the residue-producing antibacterials (Table
of Antibacterials), once used almost exclusively in health
care institutions, have been added to increasing numbers of household
products, particularly soaps and cleaning agents. A recent survey
reported that 76% of liquid soaps from 10 states in the US contained
triclosan and approximately 30% of bar soaps contained triclocarban.
Many cleaning compounds contain quaternary ammonium compounds.
Because these compounds have very long chemical names, they are
often not easily recognized as antibacterial agents on packaging
labels. More recently, triclosan has been bonded into the surface
of many different products with which humans come into contact,
such as plastic kitchen tools, cutting boards, highchairs, toys,
bedding and other fabrics.
Is
the use of antibacterial agents regulated in the US?
Whether
or not an antibacterial agent is regulated depends upon its intended
use and its effectiveness. The US Food and Drug Administration
(FDA) regulates antibacterial soaps and antibacterial substances
that will either be used on the body or in processed food, including
food wrappers and agents added to water involved in food processing.
If a substance is not intended for use on or in the body, it is registered by the US Environmental Protection Agency (EPA) under the Federal Insecticide, Fungicide, and Rodenticide Act. Substances are registered either as public health or as non-public health antimicrobial agents.
What
is the difference between bacteriostats, sanitizers, disinfectants
and sterilizers?
The EPA classifies public health antimicrobials as bacteriostats,
sanitizers, disinfectants and sterilizers based on how effective
they are in destroying microorganisms. Bacteriostats inhibit bacterial
growth in inanimate environments. Sanitizers are substances that
kill a certain percentage of test microorganisms in a given time
span. Disinfectants destroy or irreversibly inactivate all test
microorganisms, but not necessarily their spores. Sterilizers
destroy all forms of bacteria, fungi, and other microorganisms
and their spores.
Disinfectants can be further categorized as broad or limited spectrum
agents. A broad-spectrum disinfectant destroys both gram-negative
and gram-positive bacteria. A limited-spectrum disinfectant must
clearly specify the specific microorganisms against which it works.
How
beneficial are antibacterials?
Antibacterials
are definitely effective in killing bacteria, however, there is
considerable controversy surrounding their health benefits. The
non-residue producing agents (Table
of Antibacterials) have been used for many years and continue
to be effective agents for controlling disease organisms in a
wide variety of healthcare and domestic settings. When used under
strict guidelines of application, the residue-producing agents
have proven effective at controlling bacterial and fungal infection
in clinical settings such as hospitals, nursing homes, neonatal
nurseries and other health care facilities where there may be
a high risk of infection.
A certain few consumer products have demonstrated effectiveness
for specific conditions: antibacterial toothpaste helps control
periodontal (gum) disease; antibacterial deodorants suppress odor-causing
bacteria, and antidandruff shampoos help control dandruff. However,
to date, there is no evidence to support claims that antibacterials
provide additional health benefits when used by the general consumer.
Are
antibacterial agents safe?
When used
as directed for external surfaces, antibacterial agents are considered
to be relatively non-toxic. However, some may cause skin and eye
irritation, and all have the potential for doing harm if not stored
or used properly. Furthermore, evaluations of risk are based on
single agents, and do not consider the effects of multiple uses
or multiple compounds. Recently, triclosan has been reported in
surface waters, sewage treatment plants, the bile of fish, and
breast milk, but the significance of these findings is presently
unknown.
Do
antibacterials create resistant bacteria?
Because
of their rapid killing effect, the non-residue producing antibacterial
agents are not believed to create resistant bacteria. Resistance
results from long-term use at low-level concentrations, a condition
that occurs when consumer use residue-producing agents such as
triclosan and triclocarban. Until recently, it was accepted that
these agents did not affect a specific process in bacteria, and
because of this, it was unlikely that resistant bacteria could
emerge. However, recent laboratory evidence indicates that triclosan
inhibits a specific step in the formation of bacterial lipids
involved in the cell wall structure. Additional experiments found
that some bacteria can combat triclosan and other biocides with
export systems that could also pump out antibiotics. It was demonstrated
that these triclosan-resistant mutants were also resistant to
several antibiotics, specifically chloramphenicol, ampicillin,
tetracycline and ciprofloxacin.
Resistance to antibacterials has been found where these agents
are used continuously (as in the hospital and food industry);
however, at the present time, this modest increase in resistance
has not yet created a clinical problem.
Can
the widespread use of antibacterial agents lead to more resistant
bacteria?
Many scientists
feel that this is a potential danger, but others argue that the
laboratory conditions used in the research studies do not represent
the "real world." So far, studies of antibacterial use in home
products such as soap, deodorant and toothpaste have not shown
any detectable development of resistance. However, such products
have only been in use for a relatively short period of time and
studies of their effects are still extremely limited.
Are
there other concerns about the use of antibacterial agents?
Yes, experts
believe that the use of these agents creates a false sense of
security that may cause individuals to become lax in their hygiene
habits. Antibacterial use should not be considered an alternative
to normal hygiene, except where normal hygiene practices are impossible.
It should always be remembered that most bacteria are harmless
and in many cases, even beneficial. Very few bacteria actually
cause disease. Antibacterials are not discriminating and an all-out
attack on bacteria in general is unjustified. Constant use of
disinfecting agents tends to disrupt the normal bacteria that
act as barriers against invading pathogens. This may cause shifts
in bacterial populations and create a "space" for disease-causing
bacteria to enter and establish infection.
In addition, some scientists have gathered evidence showing that
overly hygienic homes during early childhood may be linked to
the appearance of allergies later in life. In this "hygiene hypothesis,"
allergies develop because the childhood immune system fails to
mature properly due to lack of contact with immune-stimulating
bacteria. This hypothesis remains controversial and requires further
research for validation.
Are
there other effective cleaning methods to prevent disease spread?
For most
purposes, washing with regular soap and rinsing with running water,
followed by thorough drying is still considered the most important
way of preventing disease transmission (see Hand
washing). This is especially important after using the toilet,
changing a diaper, emptying a diaper pail, cleaning the toilet,
or after handling raw meat or poultry. Several common traditional
agents are effective against a wide range of disease-causing organisms.
These include 70% solutions of ethyl or isopropyl alcohol, household
bleach and hydrogen peroxide. Unlike triclosan and other long-acting
agents, these products destroy multiple cells components at once
rather than attacking a specific bacterial process.
When
are antibacterials useful?
While there
is no evidence that the routine use of antibacterials confer a
health benefit, they are useful where the level of sanitation
is critical and additional precautions need to be taken to prevent
spread of disease. Thus, they are important in hospitals, day
care centers and healthcare facilities and other environments
with high concentrations of infectious bacteria. In the home environment,
they may be needed for the nursing care of sick individuals with
specific infections, or for those whose immune systems have been
weakened by chronic disease, chemotherapy or transplants. Under
these circumstances, antibacterials should be used according to
protocol, preferably under the guidance of a health care professional.
More information
about antibacterials
…
Handwashing: an effective way to stop the spread of infection …
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