We thank Saliou and Baron for their comments. They state that microbial surveillance of endoscopes by antegrade sampling with a sterile 0.9 % saline solution might be insufficient to reveal the microbial contamination. They also suggest the additional use of thiosulfate during sampling. Unfortunately, in the outbreak we described, the use of a thiosulfate-containing buffer would not have been able to detect the microbial contamination. As the manufacturer states, the elevator wire channel of the TJF-Q180V is sealed by an O-ring, which means that separate cleaning is no longer necessary. Moreover, this scope is also designed with a unique distal cap that is fixed, which impairs cleaning and disinfection in the spaces within this cap. Sampling of these spaces is only possible when using an ultrathin swab, as demonstrated in our study, which thereby revealed the VIM-2 producing Pseudomonas aeruginosa.

However, we do agree with Saliou and Baron that the optimal sampling method for endoscopes is still under debate. At present, the use of sterile 0.9 % saline solution is recommended by the European Society of Gastrointestinal Endoscopy and the European Society of Gastroenterology and Endoscopy Nurses and Associates. Although the French guideline recommends the use of a tensioactive solution (e. g. Tween 80) to increase the detection of microorganisms, the use of sodium thiosulfate is not mentioned in this guideline.

The combination of the narrow lumina of the endoscope and heavy contamination with blood, secretions, and microorganisms during its use, might promote the growth of biofilms in cases of insufficient (pre)cleaning. Once these biofilms occur, they are very resilient to physical removal by regular cleaning and are less susceptible to biocides. In a recent review, it was concluded that by ensuring prompt device cleaning and reprocessing, either by high-level disinfection or sterilization, and proper drying, biofilms will not have a chance to form [8]. Unfortunately, at present there is no evidence in the literature that a consensus on this matter has been reached.

However, in light of recent reports of microbiological outbreaks after endoscopy, a reliable method of investigating microbial safety following high-level disinfection is urgently needed. The utility of sodium thiosulfate or another biofilm dissolver should be investigated in studies, led, ideally, by an international working group consisting of microbiologists and endoscopists. In addition, a consensus statement concerning the interpretation and action required from the data collected should become available and updated regularly.

Saliou and Baron also stress the importance of endoscope drying in order to prevent bacterial proliferation. The importance of drying has been emphasized previously by Muscarella. As stated in our manuscript, at the Erasmus MC all endoscopes are dried and stored in a storage cabinet (WASSENBURG DRY 300; Wassenburg Medical Devices BV, Dodewaard, The Netherlands), unless immediate re-use (within 4 hours) is required. Therefore, bacterial proliferation during storage was not considered to be a possible cause of the VIM-2 producing P. aeruginosa outbreak.