Endoscopy is an indispensable part of contemporary medical practice. The development
of new diagnostic and therapeutic techniques has broadened its application, and the
number of endoscopies continues to rise [1]. That is a trend that is very likely to continue.
Endoscopes are generally reusable devices and have to be reprocessed through high-level-disinfection.
However, reprocessing of endoscopes is challenging as they have a complex design with
multiple long channels with small diameters. In addition, gastrointestinal endoscopes
in particular are exposed to a high load of bacteria. Studies have shown that 5 %
to 30 % of ready-to-use endoscopes are still contaminated with microorganisms after
reprocessing [2]
[3]. The danger of these contaminated endoscopes is apparent from the published outbreaks
of patient infections with mainly multi-resistant bacteria in various healthcare institutions
across the United States and Europe [4]. If an infection is caused by transmission from a contaminated endoscope, it is
referred to as an endoscope-associated infection (EAI). The exact risk of such an
EAI is not known. For duodenoscope-associated infections, a bare minimum risk of 0.01 %
has been calculated based on the three described outbreaks in the Netherlands [5]. However, EAIs are hard to recognize and are often not reported, so the actual risk
is expected to be higher [4]
[6]
[7].
Endoscope contamination studies differ greatly in which type of endoscopes are investigated,
sampling method, laboratory analyses, frequency of cultures, timing of cultures, sample
size, and interpretation of results. This makes comparing studies challenging. However,
the majority of studies point towards the overarching conclusion that current cleaning
methods are not capable of reaching a zero contamination rate.
There are many factors that potentially play a role in endoscope contamination. However,
surprisingly little is known about these risk factors. In the Netherlands, a risk
analysis of nationwide studies found a contamination rate for duodenoscopes and linear
echoendoscopes of 15 %, with no influence of endoscope age, endoscope type or usage.
Also, no differences were found between reprocessing characteristics such as type
of washer disinfectors, detergents or disinfectants [8]. Studies that did find differences in reprocessing characteristics were mainly performed
in vitro and, therefore, might not reflect clinical practice [9]
[10]
[11].
In issue 3/2023 of Endoscopy International Open, Pineau analyzed 90,311 microbiological
culture samples obtained from endoscopes from 490 different hospitals in France over
a time period of 18 years [12]. The French guideline distinguishes between high-risk endoscopes that come into
contact with a sterile environment such as choledoscopes, and endoscopes that come
into contact with mucous membranes (gastrointestinal endoscopes and bronchoscopes)
and the results of endoscope cultures are interpreted according to three categories:
1) “target level,” no contamination or an acceptable level of contamination; 2) “alert
level,” no reason for an intervention yet, but an indication that reprocessing might
not be performed properly; and 3) “action level,” contamination with > 25 colony forming
units (CFU) or presence of an indicator microorganisms including Enterobacteriaceae, Staphylococcus aureus, Pseudomonas aeruginosa, Pseudomonas species, Stenotrophomonas maltophilia, Acinetobacter species or Candida species [13].
The author found that the average ratio of endoscopes at “action level” in 2021 was
12.6 %, an improvement from 2004 (19.7 %). The number of cultures increased significantly
from 223 samples in 2004 to 18,288 cultures in 2021. In 2018, the French guideline
was updated pertaining the sampling methodology of duodenoscopes. In addition to the
channels, cultures of the distal tip are also included [14]. The author already mentions that this change in the sampling protocol is a likely
explanation for the observed increase of duodenoscopes at “action level” by 8.4 %
from 2017 to 2018 [12].
The author is to be commended for a study with such a large sample size. The study
strengthens the conclusion that contamination of endoscopes in general remains an
issue and concern. It also shows some worrying trends, such as the increase of the
contamination of linear echoendoscopes (+ 0.7 % per year). There are some methodological
issues, however, that remain unanswered, which in all probability is partly due to
the retrospective nature of the study. What was the adherence rate with regard to
the frequency of culturing according to the guidelines, in particular in earlier years?
It also remains unclear if and to what extent the same sampling method that was used
between 2004 and 2007 differs from French guideline published in 2007 according to
which all subsequent samples were collected. Although a universal sampling protocol
was issued, how was the uniformity of execution verified in so many hospitals? Does
the data include only regular surveillance cultures or also repetitive cultures from
quarantined endoscopes? This signifies the important distinction between primary contamination
and persistent contamination. In Fig. 1, the distribution of healthcare centers and their percentage of endoscopes at “target
level” is depicted. Fifteen percent of healthcare centers have more than 90 % of their
endoscopes at “target level.” Consequently, 85 % do not reach such a level, which
seems an important observation. What is the likely explanation for this observation
by either inference or preferably data analysis and are there lessons to be learned
by those who underperform? Details about which part of the endoscopes were found to
be contaminated are not reported.
Despite these critical remarks, some important lessons can be drawn from this study.
First and foremost, it reaffirms that endoscope contamination remains a clinically
relevant issue. Although not unequivocally proven by the data in the manuscript, the
update of the guideline in 2018 seems a plausible explanation for the sudden increase
in the percentage of duodenoscope contamination. This suggests that indeed, implementation
of a more careful and elaborate sampling protocol leads to identifying higher contamination
rates. This is food for thought about how to value and interpret communications from
centers that report very low contamination rates. Either those centers are centers
of excellence with regard to scope cleaning and urgently need to reveal their secrets
to those of us who seem ignorant, or their sampling and culture methodologies are
below par and are in urgent need of revision.
In summary, this study reaffirms that endoscope contamination remains an important
problem and challenge in everyday endoscopy practice. Risk factors for endoscope contamination
could not be identified although the data are very suggestive of the good old adage,
“If you search better, you will find more.”
