Healthcare Hygiene magazine October 2019 | Page 25

monitoring of their environments, either to assess cleaning
or as part of a continuous risk assessment.”
Rawlinson, et al. (2019) summarize that, “Simple CF
numbers per cm2 provided by total viable counts (TVCs)
often do not reflect the true risk to the patient, as studies
show that surfaces with the highest bioburden are not
always the surfaces with the most multidrug-resistant
organisms (MDROs) which are of greater clinical concern.
TVC sampling is frequently undertaken in order to monitor
cleaning, rather than as a risk assessment. Seventy-three
studies sampling the hospital environment were reviewed
with varying contamination of surfaces likely due to studies
using different sampling methodologies, processing methods
and targeting different organisms on different surfaces.”
The researchers conclude that, “Background environ-
mental monitoring of the hospital surface environment is
not enforced by law or legislation and hospitals are under
no obligation to monitor surfaces. Hospitals that choose
to sample may use in-house guidelines or guidelines from
the food or pharmaceutical industry. There are no compre-
hensive guidelines available for hospital sampling and there
is little evidence-based literature on efficacies of sampling
methods under different conditions which exist in the real
hospital environment.”
In Mulvey, et al. (2011)’s evaluation of three methods
for monitoring hospital cleanliness (visual monitoring, ATP
bioluminescence and microbiological screening of five clinical
surfaces before and after detergent-based cleaning), they
found that visual assessment did not reflect ATP values nor
environmental contamination with microbial flora including
S. aureus and MRSA. There was a relationship between
microbial growth categories and the proportion of ATP
values exceeding a chosen benchmark but neither reliably
predicted the presence of S. aureus or MRSA. An ATP
benchmark value of 100 RLUs offered the closest correlation
with microbial growth levels <2.5 CFU/cm2. The researchers
add, “The original quantitative standard stated that ACC on
hand-touch sites should not exceed 5 CFU/cm2 but this has
since been reduced to 2.5 CFU/cm2. The qualitative standard
states that any pathogen isolated should be <1 CFU/cm2 on
surfaces. Well-cleaned surfaces with little organic material
yield <250 RLU, whereas poorly cleaned surfaces can yield
>1,000 RLU. These values are dependent upon the make and
model of equipment used, since one RLU is not necessarily
the same as that decreed by another type.”
Mulvey, et al. (2011) indicated from the studies they
analyzed that light, moderate and heavy growth were
classified as hygiene ‘failures,’ while no growth and scant
growth were hygiene ‘passes.’ They explain, “Mean ATP
values were examined against microbial growth to assess
whether ATP levels could be used in place of microbial growth
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to predict hygiene levels. The sensitivity and specificity of
ATP at all possible benchmarks corresponding to observed
ATP values were calculated against ‘gold standard’ microbial
growth categories and used to construct a receiver operating
characteristic (ROC) curve. Both pre- and post-cleaning mea-
surements were included in this analysis. Routine cleaning
appears to have had some effect on ATP values since they
decreased by 32.4 percent for most sites … Microbial counts
also decreased after cleaning [48 percent (43/90) of sites],
although a similar proportion were similar after cleaning
as they were before cleaning [42 percent (38/90) of sites].
Just nine of 90 sites demonstrated higher microbial growth
after cleaning.”
As Mulvey, et al. (2011) observe, “As the number of
microbial colonies changes at a specific environmental site,
so does the RLU value, but the variability of RLU in a short-
term study made it difficult to choose an ATP benchmark
designed to identify unacceptable levels of soil. The lower
the benchmark is set, the more sites will fail; conversely, the
higher the benchmark is set, fewer sites will fail. We found
that the benchmark showing the closest proportionate failure
rates to a study using a 250 RLU benchmark was 100 RLU.
This value corresponded with an ACC of <2.5 CFU/cm2,
which has previously been used as a surface hygiene bench-
mark. As ATP systems become more sophisticated, these
benchmarks will continue to require revision downwards.”
They caution, “The range and diversity of the ATP results
must be carefully considered. Despite monitoring in triplicate,
occasional inflated values, for no apparent (visible) reason,
skewed the overall results. It is already known that organic
soil contains both microbial and human DNA, as well as
food debris and liquids. ATP can also be confounded by
disinfectants (bleach), microfiber products and manufactured
plastics used in cleaning and laundering industries. If ATP
assessment is introduced into hospitals, it should be on
the understanding that there will be inevitable failures that
do not necessarily indicate true infection risk for patients.
Sensitivity and specificity of 57 percent mean that the margin
for error is too high to justify stringent monitoring of the
hospital environment at present. Further work is required
to fully assess routine ATP monitoring in hospitals.”
Carling (2013) points to the concept of ‘cleanliness’
versus cleaning: “… it is important to consider the differ-
ence between assessments of cleanliness and programs to
evaluate environmental cleaning practice. Although opti-
mizing cleanliness of the patient zone surfaces represents
the goal of disinfection-cleaning practice, practical and
biologic limitations substantially preclude the isolated use
of monitoring methods that utilize cleanliness monitoring
as a surrogate for evaluating cleaning practice. A further
limitation of evaluating cleanliness rather than evaluating
cleaning practice relates to the fact that patient zone surfaces
often have an intrinsically low bioburden prior to cleaning.
Whereas it seems somewhat counterintuitive to optimize
environmental cleaning of surfaces that often have low viable
bioburdens, it is important to note that both transmissible
and infectious doses of HAPs are very low.”
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