Field Epidemiology Manual Wiki

Reprocessing of flexible endoscopes

Last modified at 4/21/2016 7:14 PM by Vladimir Prikazsky

1. Introduction.

Endoscopes are used for a variety of diagnostic, surgical, and therapeutic needs in clinical practice. The devices are often reusable and therefore require reprocessing to ensure patient safety and prevent transmission of microorganisms from one patient to the next. In recent years, there have been reported outbreaks by contaminated flexible endoscopes. The transmissions of harmful microorganisms via endoscopes are largely attributed to lapses in essential reprocessing steps. The complex design of the scopes aggravates proper cleaning due to their narrow, tight channels and microscopic crevices that cannot be easily reached. Organic debris and fluid can accumulate and settle in such tracts, enabling biofilm formation and potentially harmful microorganism growth. Therefore, proper reprocessing of endoscopes is regulated by a series of steps and procedures to ensure optimal cleaning results and thereby enhance patient safety.

2. Endoscope reprocessing.

The essential steps of endoscope reprocessing comprise several tasks and may only be performed by verifiably trained personnel:

  1. pre-treatment: following patient examination, the endoscope is immersed in an enzyme detergent solution to prevent the encrustation of patient material on the scope. Contamination of the endoscope with feces, blood, or mucus becomes more difficult to remove once they are in a dried condition;

  2. cleaning: the first and most important step in removing the microbial burden from an endoscope. Cleaning should be performed manually with a single-use soft brush to mechanically remove retained debris that may interfere with the capability of the chemical solution to effectively kill and/or inactivate microorganisms. Cleaning already reduces a portion of the microbial burden before disinfection;

  3. disinfection: high-level disinfection (HLD) in an automated endoscope washer-disinfector (AEWD) is regarded as the standard for medical devices that touch mucous membranes, such as endoscopes. This disinfection process utilizes a chemical liquid agent, heat, and humidity. Disinfection should always be performed with an automated device, not manually.

    The types of disinfectants used on endoscopes:

  • glutaraldehyde

  • phtharal

  • peracetic acid

  • highly-acidic electrolyzed water (EOW);


  1. drying;

  2. storage: endoscopes are stored in a drying closet by suspension on hangers to prevent residual moisture inside the channels. The presence of moisture inside the scope may cause bacterial growth. The drying closet must be dust and moisture free and doors must be kept closed.

3. Endoscope washer-disinfector (EWD).

The reprocessing of endoscopes should always be performed with an automated EWD. These machines are designed for automated chemothermal cleaning and disinfection and should be meet the criteria of the EN ISO 15883-4international standard. The major advantage of a EWD is that all program sequences, dosage of process chemicals, temperature adjustments are automated. Therefore, they provide process documentation of each step of the cleaning program, which allows for verification and traceability of the cleaning performance. Process validation is a measure of quality control. EWDs are also subjected to technical testing (maintenance) by a service engineer to ensure proper function.


4. Quality control (QC) of endoscopes.

QC should be regarded as a multidimensional approach. Aside from technical tests of endoscope function, microbiological testing of rinse solutions from endoscope channels should be conducted at least once per year. Additionally, retrieving swabs from the endoscope channels should be conducted. Documentation of checks carried out must be recorded in protocols to assure traceability.


  • Gastmeier P, Vonberg RP. Klebsiella spp. in endoscopy-associated infections: we may only be seeing the tip of the iceberg. Infection 2014;42:15-21.

  • Alrabaa SF, Nguyen P, Sanderson R, Baluch A, Sandin RL, Kelker D, et al. Early identification and control of carbapenemase-producing Klebsiellapneumoniae, originating from contaminated endoscopic equipment. Am J Infect Control 2013;41:562-4.

  • Kovaleva J, Peters FT, van der Mei HC, Degener JE. 2013. Transmission of infection by flexible gastrointestinal endoscopy and bronchoscopy. Clin Microbiol Rev 26:231–254.

Available material.

  • EN ISO 15883-4:2008(en). Washer-disinfectors - Part 4: Requirements and tests for washer-disinfectors employing chemical disinfection for thermolabile endoscopes. Updated 2011. International Organization for Standardization.

Original contribution from:

Elisabeth Presterl, Clinic for Hospital Hygiene and Infection Control, Medical University of Vienna, Vienna General Hospital, Austria.