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\begin{document}

\title{UV-C light: the future of disinfection of flexible endoscopes without a
working channel?}



\author[1]{Yana Halmans}%
\author[1]{David Wellenstein}%
\author[1]{Michael Romijn}%
\author[1]{Suzan Cremers}%
\author[1]{Jannie J. Smit}%
\author[1]{Joost Hopman}%
\author[1]{Robert Takes}%
\author[1]{Guido van den Broek}%
\affil[1]{Radboudumc}%


\vspace{-1em}



  
  \date{March 14, 2025}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
\textbf{Objective:} To investigate Colony-Forming Unit (CFU) reduction
on contaminated flexible endoscopes without a working channel after UV-C
light disinfection compared to the current disinfection method with the
Endoscope Washer Disinfector. \textbf{Design, setting:} After
pharyngolaryngoscopy, a manual pre-cleaning with tap water was
performed. A culture was then collected by rolling the distal 8-10 cm of
the flexible endoscope over an Agar plate. The flexible endoscope was
disinfected using the D60 (60-second disinfection process with UV-C
light) or the Endoscope Washer Disinfector (golden standard reprocessing
process with water and chemicals). Another culture was then taken. After
incubation, a CFU count was performed. \textbf{Results:} Two hundred
flexible endoscopes without a working channel were divided equally
between the two disinfection groups. After clinical use and manual
pre-cleaning, 84 of the 100 (84.0\%) (UV-C light group) and 79 of the
100 (79.0\%) (EWD) flexible endoscopes were contaminated with at least 1
CFU. Flexible endoscopes that showed no contamination after use were
excluded from further analysis. After disinfection with UV-C light, 72
(85.7\%) flexible endoscopes showed no contamination (i.e. 0 CFUs)
versus 66 (83.5\%) flexible endoscopes after reprocessing with the
Endoscope Washer Disinfector. \textbf{Conclusion:} There is no
difference in CFUs reduction on contaminated flexible endoscopes without
a working channel between UV-C light disinfection and the current gold
standard, the Endoscope Washer Disinfector.%
\end{abstract}%



\sloppy


\textbf{UV-C light: the future of disinfection of flexible endoscopes
without a working channel?}

UV-C light disinfection within otolaryngology

\par\null

\textbf{Abstract}

\textbf{Objective} \textbf{:} To investigate Colony-Forming Unit (CFU)
reduction on contaminated flexible endoscopes without a working channel
after UV-C light disinfection compared to the current disinfection
method with the Endoscope Washer Disinfector.

\textbf{Design, setting:} After pharyngolaryngoscopy, a manual
pre-cleaning with tap water was performed. A culture was then collected
by rolling the distal 8-10 cm of the flexible endoscope over an Agar
plate. The flexible endoscope was disinfected using the D60 (60-second
disinfection process with UV-C light) or the Endoscope Washer
Disinfector (golden standard reprocessing process with water and
chemicals). Another culture was then taken. After incubation, a CFU
count was performed.

\textbf{Results:} Two hundred flexible endoscopes without a working
channel were divided equally between the two disinfection groups. After
clinical use and manual pre-cleaning, 84 of the 100 (84.0\%) (UV-C light
group) and 79 of the 100 (79.0\%) (EWD) flexible endoscopes were
contaminated with at least 1 CFU. Flexible endoscopes that showed no
contamination after use were excluded from further analysis. After
disinfection with UV-C light, 72 (85.7\%) flexible endoscopes showed no
contamination (i.e. 0 CFUs) versus 66 (83.5\%) flexible endoscopes after
reprocessing with the Endoscope Washer Disinfector.

\textbf{Conclusion:} There is no difference in CFUs reduction on
contaminated flexible endoscopes without a working channel between UV-C
light disinfection and the current gold standard, the Endoscope Washer
Disinfector.

\textbf{Keywords:} flexible endoscopes without a working channel,
disinfection, UV-C light disinfection, Endoscope Washer Disinfector

\textbf{Key points:}

Flexible endoscopes without a working channel are indispensable
instruments within otolaryngology, but the reprocessing process can be
improved.

UV-C light disinfection can be an alternative for disinfection of
flexible endoscopes without a working channel.

\textbf{Introduction}

In otorhinolaryngology (ORL), flexible endoscopes without a working
channel (FEs) are used to examine the nasal cavity, pharynx and larynx.
FEs are frequently used and thus reprocessed several times a day.
Previous research demonstrated that contamination with secretions, blood
and microorganisms after use can be extensive(1). Inadequate
reprocessing of endoscopes is considered the most important factor of
contamination from endoscopy procedures, possibly resulting in outbreaks
of health-care-associated infections(2). Therefore, thorough
reprocessing of FEs is critical for limiting pathogen transmission and
reducing infections.

To determine the strategy for sterilization or disinfection of a
specific medical devices, the level of disinfection is determined. There
are three disinfection levels: high, intermediate and low-level
disinfection. Each disinfection level can be distinguished from one
another based on the specific marker or indicator microorganisms that
each can or cannot destroy. According to Spaulding's classification
scheme, FEs are considered semi-critical medical devices and require
high-level disinfection(3).

Several standard guidelines for reprocessing endoscopes have been
developed by several professional organizations, such as the European
Society for Gastrointestinal Endoscopy(ESGE), the American Society for
Gastrointestinal Endoscopy(ASGE), the Healthcare Infection Control
Practices Advisory Committee(HICPAC) and the Dutch Flexible Endoscopes
Cleaning and Disinfection Steering Committee(SFERD) or guidelines are
provided by the manufacturer of the FEs(4-7). No international standard
has been implemented and the methods used are often time-consuming. This
could lead to longer waiting times for patients, or additional costs,
because the long reprocessing times require more FEs in inventory. In
addition, large amounts of water and chemicals are used. Disinfection
with ultraviolet light(UVL) could be an alternative method.

UVL can be divided into three groups depending on the length of their
bands: A(315-400 nm), B(280-315 nm) and C(100-280 nm)(8). UVL group
C(UV-C) is known to be the most harmful to living organisms, with peak
efficiency at 254nm(8).

Previous research has shown that UVL disinfection of medical surfaces
can be highly effective in reducing microorganisms, such as Clostridium
difficile, Methicillin-resistant Staphylococcus aureus (MRSA),
biofilm-forming bacteria and fungal spores(9-12). UV-C light
disinfection for ORL endoscopes showed a bacterial reduction of
10\textsuperscript{6} Colony Forming Units(CFUs) for rigid endoscopes
and a 10\textsuperscript{7} CFU reduction for FEs(13, 14).

The current reprocessing method for FEs is done using water and
chemicals with the Endoscope Washer Disinfector (EWD). However, this
process is time-consuming and should therefore be improved. UV-C light
disinfection has shown to be a promising tool for surface and endoscope
disinfection in previous research. The goal of this study was to
investigate the CFU reduction on contaminated FEs without a working
channel after UV-C light disinfection, compared to the current
disinfection method with the EWD.

\textbf{Materials and Methods}

\emph{Setting}

This study was performed at the department of Otorhinolaryngology and
Head and Neck Surgery of the Radboud university medical center, a
tertiary university hospital in The Netherlands. From January 2022 until
May 2022, FEs without a working channel were examined. The FEs were used
to examine the nasal cavity, pharynx or larynx of the entire spectrum of
ORL patients(infectious and non-infectious patients). To evaluate the
effectiveness of UV-C light disinfection, only contaminated FEs without
a working channel(VNL9-CP, PENTAX Medical B.V., Dodewaard, The
Netherlands) were used. FEs without a working channel that showed no
contamination after clinical use and manual pre-cleaning were excluded,
since assessing the disinfection process in these FEs was impossible.

The used FEs were randomly assigned to the UV-C light group (group 1) or
the Endoscope Washer Disinfection group (group 2). In order to make the
disinfection process, culture collection and assessment as standardized
as possible, they were performed by two researchers(YH and MR). Before
the start of the study, both researchers were trained in these tasks by
a senior infection prevention specialist(SC).

As protocolled by the hospital, FEs without a working channel should
receive a manual pre-cleaning using water and chemicals in order to
remove visible dirt and debris. However, to best evaluate the
disinfection process itself, in this study pre-cleaning was performed
using only water. A gauze pad was moistened with tap water and moved
several times in a rotary motion from proximal to distal across the FE
to remove visible debris. A culture was then taken from the FE(culture
1). Next, the FE was placed and disinfected for 60 seconds in the D60
UV-C light disinfector(group 1), or for 22 minutes in the EWD(group 2).
After disinfection, a new culture was taken(culture 2). To not interfere
with current patient safety regulations, all FEs were finally
reprocessed by the EWD, as protocolled by our hospital. Due to mandatory
changes in reprocessing logistics during our study, some FEs in group 2
were reprocessed in a central processing department and received
additional manual pre-cleaning with Neodisher\selectlanguage{ngerman}® MediClean forte(Dr.
Weigert Nederland B.V., Assen, The Netherlands).

\emph{Microbiological culture}

A rolling method over a Plate Count Agar+additives(Balis Laboratorium
BV, Boven-Leeuwen, The Netherlands) was used to evaluate the bacterial
contamination. The distal 8-10 cm of the FE and the tip were cultured.
The FE was rolled over the agar plate until the entire circumference had
touched the plate. Sterile tweezers were used to fix the FE, to prevent
partial lifting of the FE from the plate. The cultures were incubated at
36°C for 72 hours. A more detailed protocol can be found in Appendix 1.

\emph{Microbiological evaluation}

After incubation, the number of bacteria on the agar plates were
quantified by counting CFUs, indicating the level of microbiological
contamination(15).

\emph{The D60 UV-C light disinfector}

Using UV-C light, the D60(UV Smart Technologies B.V., Rijswijk, The
Netherlands) disinfects the outer surfaces of channelless invasive
medical devices in 60 seconds. The technology operates at a wavelength
ranging from 100-280nm (peak at 253.7nm). According to the
manufacturer's internal research(available upon request at the
manufacturer), a microorganism reduction of at least a log-4 is
achieved.

The used endoscope is placed inside a glass holder, allowing the UV-C
light to reach the endoscope without the occurrence of shadowing. The
disinfection chamber is completely sealed off during a disinfection
cycle, preventing UV-C light from reaching the user. No chemicals or
liquids are required for the disinfection process other than the those
used for manual pre-cleaning, which remains necessary since UV-C light
cannot penetrate dirt, debris and grime (16).

\emph{The Endoscope Washer Disinfector}

The EWD disinfects medical devices using water and chemicals.
Afterwards, the FEs are dried and stored until transportation. Multiple
devices can be reprocessed at the same time, but the duration of the
reprocessing depends on the brand and type of EWD. In this study the
WD440PT(Wassenburg Medical Nederland, Dodewaard, The Netherlands) with
accompanying chemicals(EndoHigh PAA \& Detergent) was used.

\emph{Statistics}

Statistical significance was determined with a Chi-square test and
Fisher's Exact test. Data were analyzed using SPSS software, version
25(IBM Corporation, Armonk, NY, USA). A p-value of \textless{}0.05 was
considered to be statistically significant.

\emph{Ethical approval}

The research ethics committee of the Radboud University Medical Centre
decided that this study would be carried out per the applicable
legislation concerning reviewal by an accredited research ethics
committee, such as Medical Research involving Human Subjects Act and
Medical Treatment Contracts Act(file number 2021-9837).

\textbf{Results}

\emph{General results}

200 FEs without a working channel were collected and evenly distributed
among the disinfection groups.

\emph{Results before disinfection}

Immediately after clinical use and manual pre-cleaning, a CFUs count
ranging from 0 CFUs to countless CFUs(\textgreater{}500) was found(Table
1). In total, 16 of the 100 FEs in group 1 and 21 of the 100 FEs in
group 2(EWD) showed no contamination(i.e., 0 CFUs) before disinfection
and were excluded from additional analyses. After exclusion of the FEs
that showed no contamination, a chi-square test was performed showing no
statistically significant difference in the distribution of FEs
depending on the CFUs count before disinfection between the study
groups(p=0.72).

\emph{Results after disinfection}

After disinfection with UV-C light, a total of 72 of the 84(85.7\%) FEs
showed 0 CFUs. After disinfection using the EWD a total of 66 of the
79(83.5\%) FEs showed 0 CFUs(Figure 1). A chi-square test showed no
statistically significant difference in the distribution of FEs
depending on the CFUs count after disinfection between study
groups(p=0.70). In total, 12 FEs in group 1(D60) and 13 FEs in group
2(EWD) were still contaminated after disinfection in a CFU count ranging
from 1 to \textgreater{}50.

A total of 56 FEs in the EWD group were disinfected centrally.
Subanalysis showed no statistically significant difference in CFUs
between FEs centrally versus FEs non-centrally disinfected in both the
sample taken before(p=0.53) and after(p=0.82) disinfection.

One FE in group 1 was more contaminated after disinfection(1 CFU) than
before(0 CFUs). Two FEs in group 2 showed more contamination(4 and 1
CFUs) after disinfection than before (both 0 CFUs).

\textbf{Discussion}

Current reprocessing methods with the EWD are time-consuming and UV-C
light disinfection seems a promising alternative. However, a study
comparing UV-C light disinfection of FEs without a working channel with
the EWD was still missing.

Guidelines describing disinfection methods determined that a log 4
reduction in CFU formation after disinfection is considered an
acceptable disinfection method(17). In our study, the Agar plates were
contaminated with CFUs in a wide range, often less than 100 CFUs.
Therefore, it was not possible to achieve a log 4 reduction. In previous
research, a threshold of \selectlanguage{english}[?] 2.5 CFUs/cm\textsuperscript{2} on agar
contact plates was considered acceptable based on food preparation
standards(18). The ESGE accepts a maximum total microbiological count of
\textless{}20 CFUs for fluid collected after flushing the endoscope.
Quantification of microorganisms is not recommended for cultures taken
from the outer surface of the endoscope, suggesting that the policy
should be based on the growth of indicator organisms(19). Since there is
no consensus on the acceptable CFUs count on FEs without a working
channel after disinfection, we agreed that 0 CFUs after disinfection was
considered a safely disinfected FE.

In total, 12 FEs in group 1(D60) and 13 FEs in group 2(EWD) were still
contaminated after disinfection. However, since no bacterial
identification was performed, no statements can be made about whether
bacteria found were commensal flora or pathogens.

In three FEs(1 D60, 2 EWD), the culture after disinfection showed a
higher number of CFUs than before disinfection. This can be explained by
several reasons. First, the study took place under clinical conditions,
where handling the FEs under unsterile conditions may have affected the
results. Second, the contamination could have been caused by the
disinfection method (D60 or EWD) or during transportation to the second
culture taking. The most plausible reason is the limited sensitivity of
the culture method.

There is no standardized method for culture collection from FEs. Methods
used to determine surface contamination include swabs, contact plates,
sponges, broths, quantitative polymerase chain reactions and dip
slides(20). Specific guidelines for culturing ORL endoscopes do not
exist, but several organizations such as the ESGE, the European Society
of Gastroenterology and Endoscopy nurses and Associates(ESGENA) and the
Gastroenterological Society of Australia provide recommendations for
microbiological monitoring of FEs(19, 21). However, their suggested
sampling methods include liquid samples from endoscope channels, which
is impossible for FEs without a working channel. The ESGE-ESGENA
guideline additionally recommends a swab method to evaluate the
contamination of the surface of the endoscope(19). Prior to this study,
we conducted a pilot comparing three commonly described sampling
methods, which will be submitted shortly. The three sampling methods
compared were: a rolling method on an Agar plate, swab method and broth
method for sampling FEs without working channel. We found that all
sampling techniques were capable of detecting microbiological
contamination. However, practical difficulties lead to a preference for
the rolling technique.

Previous studies investigating UV-C light disinfection in ORL showed a
high bacterial load with an average value of 66.908 CFUs and 916.7
CFUs(13, 14). This is inconsistent with the contamination found in this
study on the FEs after clinical use. A possible explanation could be
that Rudhart et al (13) used rigid endoscopes, which have a different
surface texture than FEs. Due to the surface properties and flexible
property of the FEs, the rolling method may be easier to perform on the
rigid endoscope than on the FEs. In the following study by Rudhart et
al(14), the FEs were sampled directly after clinical use. In our study,
the FEs first underwent pre-cleaning before sampling. The pre-cleaning
may have already reduced microbiological contamination, resulting in
lower bacterial contamination.

In addition to the advantage of time reduction, UV-C light disinfection
has additional advantages. UV-C light disinfection does not use water or
chemicals except for pre-cleaning. Because of the short disinfection
process, fewer FEs and storage capacity are needed. These factors
contribute to a reduction in costs and environmental impact.

Limitations of this study were that we did not investigate non-bacterial
pathogens on the FEs. Literature described some cases of viral and
fungal cross-contamination in gastrointestinal endoscopic
procedures(22). Presumably, ORL FEs without a working channel also
carries the potential to transmit viral or fungal pathogens. Previous
research has shown that UV-C light has the potential to inactivate viral
and fungal pathogens(11, 23). Based on previous research, it is very
unlikely that a FE carries the potential to transmit prion disease(24).
Previous research has shown that the absorption spectra of peptide bonds
in prions are between 190 and 230nm, indicative of susceptibility to UV
light. Further research is needed to determine the UV
susceptibility(25). Furthermore, we did not perform a bacterial
identification. Thus, we cannot make any statements about whether the
bacteria found were commensal flora or pathogens. The efficacy of UV-C
light disinfection greatly relies on the manual pre-cleaning since UV-C
light cannot penetrate through dirt, debris and grime. Since the
pre-cleaning is a manual process, the quality of the pre-cleaning may
vary per person performing the process. Thus, when UV-C light
disinfection is implemented, the process of manual pre-cleaning requires
extra attention in the instruction for employees who will perform the
UV-C light disinfection. This could have led to a potential bias in our
study. Due to the logistical decision of the hospital to move the
disinfection process of FEs without a working channel to the centralized
reprocessing department, some FEs in group 2 were centrally reprocessed.
These FEs were additionally pre-cleaned with Neodisher(r) MediClean forte
(Dr. Weigert Nederland B.V., Assen, The Netherlands). However, after
reprocessing, CFUs counts showed no marginal gain for using centralized
reprocessing over decentralized reprocessing in the EWD. Finally, we did
not perform a power analysis for the number of FEs studied. The study
group is relatively small and the results should be confirmed with a
larger sample size in a multicenter setting.

\textbf{Conclusion}

This single center study investigated the CFUs reduction on contaminated
FEs without a working channel after UV-C light disinfection compared to
the current golden standard reprocessing process using the EWD. The
findings of this study show that there is no difference in CFU reduction
between UV-C light disinfection compared to the current reprocessing
process with the EWD. UV-C light disinfection could be a good
alternative for disinfecting FEs without a working channel. However, the
effectiveness of UV-C light disinfection depends on the diligence van
the pre-cleaning process.

\textbf{References}

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3. Spaulding EH. Disinfection, sterilization and preservation. Chemical
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14. Rudhart SA, Gunther F, Dapper L, Thangavelu K, Geisthoff UW,
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\textbf{Titles/captions for each figure}

Figure 1: Number of flexible endoscopes (FEs) depending on the Colony
Forming Units (CFUs) count after disinfection by disinfection group
(p=0.70).

\textbf{Appendix}

Appendix 1: Detailed protocol of the rolling method used for sampling
flexible endoscopes without a working channel

\emph{The rolling technique over a Plate Count Agar + additives:}

\begin{enumerate}
\tightlist
\item
  Immediately after pharyngolaryngoscopy, transport the FE without a
  working channel to the designated room for manual pre-cleaning and
  sample collection in the following manner:
\item
  The executor of the pharyngolaryngoscopy closes the transport
  container with the cover with the red smiley.
\item
  The assistant collects the FE immediately and brings it to the
  assigned room for manual pre-cleaning and sample collection. The
  researcher will now start the procedure.
\item
  Manual pre-cleaning:
\item
  Remove the cover with the red smiley face from the transport
  container.
\item
  Perform hand disinfection and put on unsterile gloves.
\item
  Moisten an unsterile 10x10cm gauze pad with tap water (not too wet! No
  water should drip when squeezing the moistened gauze).
\item
  Wipe the moistened gauze over the FE using a rotary motion from
  proximal to distal. Repeat three times with a different portion of the
  gauze each time. Include the tip as well. If there is still visible
  debris left on the FE, repeat until all the debris is removed.
\item
  Discard the gauze and place the FE back in the transport container.
\item
  Remove unsterile gloves and perform hand disinfection.
\item
  Collection the sample:
\item
  Use the tip and the first 10cm of the distal part of the laryngoscope
  for the sample.
\item
  Wear a medical face mask and unsterile gloves during the sample
  collection to avoid contamination. Make sure not to touch the tip and
  the first distal part of the FE except for sample collection.
\item
  Perform hand disinfection and disinfect the surface the sample
  collection will take place on using disinfection wipes.
\item
  Open the package of sterile tweezers, but do not remove the tweezers
  yet.
\item
  Remove the lid from the Plate Count Agar + additives plate.
\item
  Perform hand disinfection and put on unsterile gloves.
\item
  Fix the distal part of the FE with the sterile tweezers to prevent
  partial lifting of the FE from the plate while making a rolling motion
  with the FE. Make sure that the entire circumference of the distal end
  of the FE touched the agar plate only once.
\item
  Place the FE back in the transport container.
\item
  Remove the unsterile gloves and perform hand disinfection.
\item
  Put the lid back on the agar plate.
\item
  Record serial number of the FE, study number, date and time of the
  sample collection and sample number and label the agar plate.
\item
  Place the labeled agar plate back in the heat incubator at 36 degC
  without the addition of CO\selectlanguage{english}2 for 72 hours.
\item
  Afterwards, perform a CFUs count.
\item
  Transport the FE after the sample collection to the disinfection
  department:
\item
  Close the transportation container with the cover with the red smiley
  face facing upwards.
\item
  Transport the FE to the disinfection department and continue the
  disinfection process as protocolled by the hospital.
\end{enumerate}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure-1/Figure-1}

\end{center}
\end{figure}

\textbf{Hosted file}

\verb`Table 1.docx`  available at \url{https://authorea.com/users/625673/articles/647545-uv-c-light-the-future-of-disinfection-of-flexible-endoscopes-without-a-working-channel}

\selectlanguage{english}
\FloatBarrier
\end{document}

