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A lthough
microbiologically contaminated surfaces can serve as reservoirs
of potential pathogens, these surfaces generally are not
directly associated with transmission of infections to either
staff or patients.
The transferral of
microorganisms from environmental surfaces to patients is
largely via hand contact with the surface. Although hand hygiene
is important to minimize the impact of this transfer, cleaning
and disinfecting environmental surfaces is fundamental in
reducing their potential contribution to the incidence of
healthcare-associated infections.
According to the CDC’s
“Guidelines for Environmental Infection Control in Health-Care
Facilities,” the principles of cleaning and disinfecting
environmental surfaces take into account the intended use of the
surface or item in patient care.
The CDC retains the Spaulding
classification for medical and surgical instruments, which
outlines three categories based on the potential for the
instrument to transmit infection if the instrument is
microbiologically contaminated before use.
These categories are “critical,” “semicritical”
and “noncritical.” The CDC has
proposed an additional category designated
“environmental surfaces” to Spaulding’s
original classification to represent
surfaces that generally do not come into
direct contact with patients during care.
Spaulding proposed three levels of disinfection
for the treatment of devices and
surfaces that do not require sterility for
safe use. These disinfection levels are “high-level,” “intermediate-level,” and
“low-level.” The basis for these levels is
that microorganisms can usually be
grouped according to their innate resistance
to a spectrum of physical or chemical
germicidal agents. This information,
coupled with the instrument/surface classification,
determines the appropriate level
of terminal disinfection for an instrument
or surface.
Environmental surfaces carry the least
risk of disease transmission and can be safely decontaminated using less rigorous
methods than those used on medical instruments
and devices. Environmental surfaces
can be further divided into medical
equipment surfaces (e.g., knobs or handles
on hemodialysis machines, x-ray machines,
instrument carts, and dental
units) and housekeeping surfaces
(e.g., floors, walls, and tabletops).
The process of high-level disinfection,
an appropriate standard of treatment
for heat-sensitive, semicritical
medical instruments (e.g., flexible,
fiberoptic endoscopes), inactivates all
vegetative bacteria, mycobacteria,
viruses, fungi, and some bacterial
spores. High-level disinfection is accomplished
with powerful, sporicidal
chemicals (e.g., glutaraldehyde, peracetic
acid, and hydrogen peroxide) that are not
appropriate for use on housekeeping
surfaces.
These liquid chemical sterilants/highlevel
disinfectants are highly toxic. Use of
these chemicals for applications other than
those indicated in their label instructions
(i.e., as immersion chemicals for treating
heat-sensitive medical instruments) is not
appropriate.
Intermediate-level disinfection does not
necessarily kill bacterial spores, but it does inactivate Mycobacterium tuberculosis
var. bovis, which is substantially
more resistant to chemical germicides
than ordinary vegetative bacteria, fungi,
and medium to small viruses (with or
without lipid envelopes).
Chemical germicides with sufficient potency
to achieve intermediate-level disinfection
include chlorine-containing compounds
(e.g., sodium hypochlorite), alcohols, some
phenolics, and some iodophors. Low-level
disinfection inactivates vegetative bacteria,
fungi, enveloped viruses (e.g., human immunodeficiency
virus [HIV], and influenza
viruses), and some non-enveloped viruses
(e.g., adenoviruses).
Low-level disinfectants include quaternary
ammonium compounds, some phenolics,
and some iodophors. Sanitizers are
agents that reduce the numbers of bacterial
contaminants to safe levels as judged
by public health requirements, and are
used in cleaning operations, particularly
in food service and dairy applications.
Germicidal chemicals that have been
approved by FDA as skin antiseptics are
not appropriate for use as environmental
surface disinfectants. The selection
and use of chemical germicides
are largely matters of judgment,
guided by product label instructions,
information, and regulations. Liquid
sterilant chemicals and high-level disinfectants
intended for use on critical
and semi-critical medical/dental devices
and instruments are regulated exclusively
by the FDA as a result of
recent memoranda of understanding between
FDA and the EPA that delineates
agency authority for chemical germicide
regulation.
Environmental surface germicides (i.e.,
primarily intermediate- and low-level disinfectants)
are regulated by the EPA and
labeled with EPA registration numbers.
The labels and technical data or product literature
of these germicides specify indications
for product use and provide claims
for the range of antimicrobial activity.
The EPA requires certain pre-registration
laboratory potency tests for these products to support product label claims.
EPA verifies (through laboratory testing)
manufacturers’ claims to inactivate microorganisms
for selected products and organisms.
Germicides labeled as “hospital disinfectant”
have passed the potency tests for activity
against three representative microorganisms
– Pseudomonas aeruginosa, Staphylococcus
aureus, and Salmonella choleraesuis.
Low-level disinfectants are often labeled
“hospital disinfectant” without a tuberculocidal
claim, because they lack the
potency to inactivate mycobacteria. Hospital
disinfectants with demonstrated potency
against mycobacteria (i.e.,
intermediate-level disinfectants) may list
“tuberculocidal” on the label as well.
Other claims (e.g., “fungicidal,”
“pseudomonicidal,” and “virucidal”)
may appear on labels of environmental
surface germicides, but the designations
of “tuberculocidal hospital disinfectant”
and “hospital disinfectant” correlate directly
to Spaulding’s assessment of intermediate-
level disinfectants and
low-level disinfectants, respectively.
A common misconception in the use of
surface disinfectants in health-care settings
relates to the underlying purpose for use of proprietary products labeled as a
“tuberculocidal” germicide. Such products
will not interrupt and prevent the
transmission of TB in health-care settings
because TB is not acquired from environmental
surfaces. The tuberculocidal
claim is used as a benchmark by which
to measure germicidal potency.
Because mycobacteria have the highest
intrinsic level of resistance among the
vegetative bacteria, viruses, and fungi, any
germicide with a tuberculocidal claim on
the label (i.e., an intermediate-level disinfectant)
is considered capable of inactivating
a broad spectrum of pathogens,
including much less resistant organisms
such as bloodborne pathogens (e.g., hepatitis
B virus [HBV], hepatitis C virus
[HCV], and HIV).
It is this broad spectrum capability,
rather than the product’s specific potency
against mycobacteria, that is the basis for
protocols and OSHA regulations indicating
the appropriateness of using tuberculocidal
chemicals for surface disinfection.
The following factors influence the
choice of disinfection procedure for environmental
surfaces: a) the nature of
the item to be disinfected, b) the number of microorganisms present, c) the innate
resistance of those microorganisms to the
inactivating effects of the germicide, d)
the amount of organic soil present, e) the
type and concentration of germicide
used, f) duration and temperature of germicide
contact, and g) if using a proprietary
product, other specific indications
and directions for use.
Cleaning is the necessary first step of
any sterilization or disinfection process.
Cleaning is a form of decontamination
that renders the environmental surface
safe to handle or use by removing organic
matter, salts, and visible soils, all of
which interfere with microbial inactivation.
The physical action of scrubbing
with detergents and surfactants and rinsing
with water removes large numbers of
microorganisms from surfaces. If the surface
is not cleaned before the terminal reprocessing
procedures are started, the
success of the sterilization or disinfection
process is compromised.
❑
Source: “Guidelines for Environmental
Infection Control in Health-Care Facilities:
Recommendations of CDC and
the Healthcare Infection Control Practices
Advisory Committee (HICPAC).” |
