Healthcare Hygiene magazine October 2019 | Page 23

(7.7 percent) showed >5 CFU/cm 2 microbial growth. Bed
frames, telephones and computer keyboards were among
the surfaces that yielded a high total viable count. The
researchers suggested that combining both standards would
give a more effective method of assessing the efficacy of
cleaning/disinfection strategy.
Nante, et al. (2017) remind us that “…methods to assess
hospital environments cleaning can be considered an integral
part of infection prevention and control programs. Among
these, the most known and used are visual inspection,
microbial methods, fluorescent markers and adenosine
triphosphate (ATP) bioluminescence. The latter measures
the presence of ATP on surfaces. The ATP bioluminescence
consists in a swab, used to sample a standardized area,
which, subsequently, is placed in a tool that uses the firefly
enzyme ‘luciferase’ to catalyze the conversion of ATP in
adenosine monophosphate (AMP): this reaction results
into an emission of light which is detected by the biolumi-
nometer and quantified in relative light units (RLUs). The
presence of ATP on surfaces, obviously, is a proxy of organic
matter and, consequently, of microbial contamination. This
method has been used in food industries for over 30 years.
Its use in the healthcare environment is growing, but it is
still controversial, in that different tools consider different
threshold values, and, therefore, this technique seems not
to be standardized.”
Around the same time as the Al-Hamad and Maxwell
(2008) paper, Lewis, et al. (2008) acknowledged that,
“Calls have been made for a more objective approach to
assessing surface cleanliness. To improve the management
of hospital cleaning the use of ATP in combination with
microbiological analysis has been proposed, with a general
ATP benchmark value of 500 RLU for one combination of
test and equipment.”
In their study, Lewis, et al. (2008) used this same test
combination to assess cleaning effectiveness in a 1,300-
bed teaching hospital after routine and modified cleaning
protocols. Based upon the ATP results a revised stricter pass/
fail benchmark of 250 RLU is proposed for the range of
surfaces used in this study. This was routinely achieved using
modified best practice cleaning procedures which also gave
reduced surface counts with, for example, aerobic colony
counts reduced from >100 to <2.5 CFU/cm2, and counts
of Staphylococcus aureus reduced from up to 2.5 to <1
CFU/cm2 (95 percent of the time). The researchers say that
benchmarking is linked to incremental quality improvements
and both the original suggestion of 500 RLU and the revised
figure of 250 RLU can be used by hospitals as part of this
process, and that they can also be used in the assessment
of novel cleaning methods.
The Methods of Monitoring “Clean”
Carling (2013) reminds us that, “Effective strategies
are required to assess the effectiveness of environmental
cleaning and disinfection in healthcare settings to reduce
HAIs. One of the most basic ways to assess contamination
following environmental cleaning and disinfection is visual
inspection but concerns about the adequacy of visual
inspection alone have necessitated the development of
www.healthcarehygienemagazine.com • october 2019
technology-based approaches, such as the use of ACCs,
which are a culture-based method for assessing environ-
mental contamination; other methods include the use of
invisible fluorescent markers placed on high-touch room
surfaces before cleaning, with UV light inspection following
cleaning. Bioluminescence-based ATP assays have been
developed as another alternative that offers direct, rapid
feedback and provides a quantitative measure of cleanliness;
however, the detected presence of ATP does not necessarily
indicate viable pathogens on the tested surface. As genomic
and polymerase chain reaction (PCR)-based technologies
become less expensive and more widespread, these may
also have a role in assessing environmental contamination
and effectiveness of disinfection.”
As we have seen, the challenge, Carling (2013) acknowl-
edges, is that there is the need for identifying standardized
criteria for determining that surfaces are “clean” using
these monitoring modalities: “At the heart of the issue is
that while routine cleaning and disinfection strategies may
not result in a completely sterile environment, consensus
is needed on the threshold of contamination below which
pathogen transmission is minimized and can be considered
safe. Studies have emphasized the importance of monitoring
the operational processes associated with cleaning and
disinfection practices, and properly training and managing
environmental services personnel tasked with these duties,
are additional elements necessary for preventing transmission
of HAIs. Strategies for assessing compliance may include
use of checklists, direct observation (open or covert), and
surveys of personnel and patients. Process evaluation and
improvement should also consider important human factors
and logistical concerns that interact with environmental
cleaning procedures, including workflow, staffing, staff
training and supervision, collaboration between support
services and clinical staff, institutional leadership, and
patient preferences.”
Casini, et al. (2018) confirm that “Although not validated,
microbiologic standards for a safer hospital environment
have been proposed as three colony-forming units (CFU)/
cm2 on surfaces; this value is related to an ATP value of 100
RLU/100cm 2 . Maintaining counts below these thresholds
may assist in reducing HAIs.”
The researchers add, “Several methods have been used
to assess environmental cleanliness; one such method is the
ACC assay, which reveals the amounts of cultivable bacteria
present on surfaces. The original quantitative ACC-based
standard for defining the surfaces in a ward environment
as clean was less than 5 CFU/cm2, but this value has been
reduced to 3 CFU/cm2. Currently, the non-culture ATP
bioluminescence assay is extensively used to evaluate clean-
liness because readings can be obtained on site. Because
of its presence in living organisms, ATP was first used as an
indicator of cleanliness in the food industry. Subsequently,
ATP measurements have been employed to assess hospital
cleanliness using different benchmark values expressed in
RLUs. Quantitative results are available in less than 5 min-
utes with these assays; this makes it possible for infection
prevention or housekeeping staff to monitor the adequacy
of cleaned surfaces. The microbial evaluation of surfaces
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