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Endoscopy 2015; 47(11): 1058
DOI: 10.1055/s-0034-1392650
Letters to the editor
© Georg Thieme Verlag KG Stuttgart · New York

Outbreaks linked to duodenoscopes: microbiological control should be improved

Philippe Saliou
,
Raoul Baron
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Publication Date:
30 October 2015 (online)

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We read with interest the article by Verfaillie et al., which described an outbreak of Pseudomonas aeruginosa linked to duodenoscope design [1]. This represents a genuine problem emerging in the field of endoscopy, with outbreaks reported in both Europe and North America relating to duodenoscopes contaminated with carbapenem-resistant enterobacteriaceae (CRE) [2]. To date, the risk of nosocomial infection from endoscopes has been estimated to be low; however, the number of outbreaks reported seems to have increased in line with the spread of highly resistant bacteria such as CRE.

In the Verfaillie study, epidemiological investigations revealed that a novel-design duodenoscope was linked to the transmission of P. aeruginosa. However, antegrade sampling of all duodenoscopes did not reveal microbial contamination. Only by culturing samples from the recess under the forceps elevator of duodenoscopes was the VIM-2-producing P. aeruginosa detected. This means that the disinfection procedure used to clean endoscopes is not always effective, and that microbiological surveillance of an endoscope is not always able to reveal microbial contamination.

The duodenoscopes were reprocessed according to guidelines, and surveillance cultures were performed according to a standardized protocol for antegrade sampling [3]. This sampling technique involves the use of sterile saline solution to irrigate the channels of the endoscopes. In France, endoscopes are sampled by injecting the channels with 120 mL of neutralizing pharmacopoeia diluent buffer and sodium thiosulfate using sterile connectors [4]. The aim is to retrieve samples of biofilm and neutralize the peracetic acid in order to enable the culture of bacteria from the endoscope channels. Since we started using this technique, we have found the endoscope contamination rates to be relatively high in our hospital, especially for duodenoscopes [5]. The results presented in the study of Verfaillie et al. showed that the sampling technique used for microbiological surveillance did not identify P. aeruginosa. We believe that the use of saline sterile solution is not effective enough to reveal a potential microbial contamination.

Endoscope drying has been described as one of the most important steps in limiting bacterial proliferation and the risk of contamination during endoscope storage. This is particularly true for P. aeruginosa, which develops in a wet environment. We have demonstrated that the use of storage cabinets reduces microbial contamination of most endoscopes – with the exception of duodenoscopes [5]. The report by Verfaillie presents plausible evidence that the design of duodenoscopes makes adequate disinfection of the channels difficult. We also believe that duodenoscopes are difficult to dry, and that the potential risk of cross contamination is higher using this type of endoscope.

We agree that new duodenoscope designs should facilitate more efficient disinfection but we also believe that the method for assessing the microbial contamination of endoscopes should also be improved.