Endoscope storage time: assessment of microbial colonization up to 21 days after reprocessing

Published:December 05, 2014DOI:https://doi.org/10.1016/j.gie.2014.09.053

      Background

      Insufficient data exist for how long endoscopes can be stored after reprocessing. Concern about possible microbial colonization has led to various recommendations for reprocessing intervals among institutions, with many as short as 5 days. A significant cost savings could be realized if it can be demonstrated that endoscopes may be stored for as long as 21 days without risk of clinically significant contamination.

      Objective

      To demonstrate whether flexible endoscopes may be stored for as long as 21 days after reprocessing without colonization by pathogenic microbes.

      Design

      Prospective, observational study.

      Setting

      Tertiary care center.

      Endoscopes

      Four duodenoscopes, 4 colonoscopes, and 2 gastroscopes.

      Intervention

      Microbial testing of endoscope channels.

      Main Outcome Measurements

      Culture results at days 0, 7, 14, and 21.

      Results

      There were 33 positive cultures from 28 of the 96 sites tested (29.2% overall contamination rate). Twenty-nine of 33 isolates were typical skin or environmental contaminants, thus clinically insignificant. Four potential pathogens were cultured, including Enterococcus, Candida parapsilosis, α-hemolytic Streptococcus, and Aureobasidium pullulans; all were likely clinically insignificant as each was only recovered at 1 time point at 1 site, and all grew in low concentrations. There were no definite pathogenic isolates.

      Limitations

      Single center.

      Conclusion

      Endoscopes can be stored for as long as 21 days after standard reprocessing with a low risk of pathogenic microbial colonization. Extension of reprocessing protocols to 21 days could effect significant cost savings.

      Abbreviation:

      CFU (colony-forming unit)
      Endoscopes are cleaned (“reprocessed”) to prevent transmission of infection from 1 patient to another. They are categorized as semicritical medical devices by the Spaulding classification system, meaning that they contact mucosal surfaces but do not breach sterile environments.
      • Petersen B.T.
      • Chennat J.
      • Cohen J.
      • et al.
      Multisociety guideline on reprocessing flexible gastrointestinal endoscopes: 2011.
      As such, they require at least high-level disinfection, as espoused by multiple societies.
      • Petersen B.T.
      • Chennat J.
      • Cohen J.
      • et al.
      Multisociety guideline on reprocessing flexible gastrointestinal endoscopes: 2011.
      Proper reprocessing became widespread when multisociety guidelines for standardized endoscope reprocessing were first established 1988. Since that time, there have been very few reports of transmission of infection during GI endoscopy, and they are almost exclusively related to breaches in disinfection protocol or the use of defective equipment.
      • Nelson D.B.
      Infectious disease complications of GI endoscopy: Part II, exogenous infections.
      Although disinfection protocols are highly effective when applied assiduously, it is not known how long instruments may be stored before microbial colonization may occur. Because of this paucity of data, current U.S. multisociety guidelines make no recommendation for how long endoscopes may be stored after reprocessing (“shelf life”).
      • Petersen B.T.
      • Chennat J.
      • Cohen J.
      • et al.
      Multisociety guideline on reprocessing flexible gastrointestinal endoscopes: 2011.
      This has led to variability in reprocessing intervals among institutions, with many using 5-day intervals, likely based on earlier society guidelines.
      • Petersen B.T.
      • Chennat J.
      • Cohen J.
      • et al.
      Multisociety guideline on reprocessing flexible gastrointestinal endoscopes: 2011.
      Other organizations, such as the Gastroenterological Society of Australia, call for even more stringent intervals, with storage times between 12 and 72 hours, depending on type of endoscope.
      The few studies that address this issue indicate that shelving instruments for 5 to 14 days is associated with a low risk of contamination,
      • Riley R.
      • Beanland C.
      • Bos H.
      Establishing the shelf life of flexible colonoscopes.
      • Riley R.G.
      • Beanland C.J.
      • Polglase A.L.
      Extending the shelf-life of decontaminated flexible colonoscopes.
      • Rejchrt S.
      • Cermak P.
      • Pavlatova L.
      • et al.
      Bacteriologic testing of endoscopes after high-level disinfection.
      • Osborne S.
      • Reynolds S.
      • George N.
      • et al.
      Challenging endoscopy reprocessing guidelines: a prospective study investigating the safe shelf life of flexible endoscopes in a tertiary gastroenterology unit.
      • Vergis A.S.
      • Thomson D.
      • Pieroni P.
      • et al.
      Reprocessing flexible gastrointestinal endoscopies after a period of disuse: is it necessary?.
      with 1 small study of colonoscopes only showing this for up to 8 weeks.
      • Ingram J.
      • Gaines P.
      • Kite R.
      • et al.
      Evaluation of medically significant bacteria in colonoscopes after 8 weeks of shelf life in open air storage.
      We aimed to demonstrate whether duodenoscopes, gastroscopes, and colonoscopes may be stored for as long as 21 days without microbial colonization by potential pathogens.

      Methods

      This was a prospective, observational study conducted at the Medical University of South Carolina from August to October 2013. The endoscopes used in this study were in active use in our unit before the study and only taken out of circulation for the duration of the study. They included 4 duodenoscopes, 4 colonoscopes, and 2 gastroscopes (Olympus Medical, Center Valley, Pa). All personnel in this unit responsible for endoscope reprocessing are certified endoscopy technicians and follow standard of care protocols for mechanical cleaning and high-level disinfection by using an automated endoscope reprocessor. This study did not include human subjects or identifiers and was thus given exempt status by the Institutional Review Board of the Medical University of South Carolina.

      Endoscope reprocessing

      Each endoscope was cleaned per institutional protocol, in accordance with published guidelines.
      Society of Gastroenterology Nurses and Associates
      Standards of infection control in reprocessing of flexible gastrointestinal endoscopes.
      This involves manually wiping the endoscope with enzymatic detergent (Intercept; Medivators Inc, Minneapolis, Minn) at the bedside until all visible debris is removed. The endoscope is then suctioned with the same solution. The endoscope is then transported to a dedicated reprocessing area where each channel as well as the length of the endoscope is leak tested with clean water. If no leaks are present, the channels are brushed with detergent and the endoscope is again manually cleaned with enzymatic detergent. The endoscope is then connected to a sink that purges each channel at specified pressures. Subsequently, the endoscope and each channel are rinsed with filtered water. Air is then blown through each channel to dry. All surfaces of the endoscope are then visually inspected. After this, the endoscope is placed into the automated reprocessor (Medivators DSD-201; Medivators Inc) and undergoes high-level disinfection with a 2.5% glutaraldehyde solution (Rapicide; Medivators Inc). At the end of the 27-minute disinfection cycle, the endoscope is flushed with filtered water, followed by alcohol and then air. It is then stored hanging vertically without valves in a dust-free, ventilated cabinet with a removable drip tray (InnerSpace 4000 Series Metal Roll Top Scope Cabinet; Stanley Healthcare, Grand Rapids, Mich). This cabinet also included endoscopes that were in active use and was left open during the day but closed at night for security.

      Sample collection

      All microbiological samples were collected by 2 registered nurses, 1 of whom is a certified gastroenterology registered nurse of 13 years, with 12 years of previous experience as an endoscopy technician (J.F.) and the other an infection control practitioner (B.G.). The samples were collected immediately after high-level disinfection on day 0, then stored hanging in a dust-free cabinet until they were removed (but not reprocessed) for sample collection on days 7, 14, and 21.
      Before collecting samples, each nurse performed hand hygiene and donned a sterile gown and gloves. Samples were collected from each endoscope channel on days 0, 7, 14, and 21, making a total of 96 samples. For duodenoscopes, samples were first collected from the elevator wire channel, followed by the suction channel and biopsy port, the latter 2 being in the same order for colonoscopes and gastroscopes. For the elevator channel, 3 mL of sterile water was irrigated via a 3-mL Luer lock syringe (Becton, Dickinson, Franklin Lakes, NJ) 3 times, for a total collection of 9 mL. The sample collection technique for the suction and biopsy ports was the same, whereby they were first irrigated with 30 mL of sterile water. Next, a sterile brush was inserted through the channel and advanced 2 inches beyond the endoscope tip. Sterile scissors were then used to cut the brush, allowing it to drop into a sterile specimen cup.

      Microbial testing

      A 1-mL aliquot of each well-mixed sample was inoculated onto trypticase soy agar with 5% sheep blood (blood agar), thioglycollate broth, a CDC anaerobic blood agar plate, and Sabouraud dextrose agar (for yeast and molds). All media were incubated at 25° to 35° Celsius for 7 days. Organisms were identified by using standard microbiological techniques; results were reported in colony-forming units (CFU) per milliliter.

      Data analysis

      Numbers and percentages of positive cultures were calculated in total and by type of endoscope, organism, channel, and day.

      Results

      There were 33 positive cultures from 28 of the 96 sites tested (29.2% overall contamination rate). Most positive cultures grew 1 CFU/mL or less (ie, grew in thio broth only). The majority of isolates, 29 of 33, were typical skin or environmental contaminants, thus clinically insignificant (Table 1). The most common of these was coagulase-negative Staphylococcus (n = 18), followed by Micrococcus (n = 6), Bacillus (n = 3), Corynebacterium (n = 1), and Propionibacterium acnes (n = 1). Only 3 cultures grew more than 1 CFU/mL: 1 culture grew 5 CFU/mL Corynebacterium, a second culture grew 8 CFU/mL of coagulase-negative Staphylococcus, and 1 culture, a duodenoscope elevator, grew 49 CFU/mL of Micrococcus. There was only 1 instance where the same microbe was isolated on the same channel of the same endoscope at different time points (1 CFU/mL Micrococcus on days 7 and 21 on the biopsy channel of a colonoscope).
      Table 1Nonpathogens
      MicrobeTotal positive culturesC-scopeD-scopeG-scopeSuction channelBiopsy channelElevator
      CNS182434113
      Micrococcus6220231
      Bacillus3111120
      Corynebacterium1010010
      Propionibacterium acnes1010010
      C-scope, Colonoscope; D-scope, duodenoscope; G-scope, gastroscope; CNS, coagulase-negative Staphylococcus.
      Four isolates represented potential pathogens (4.2% of 96 sites tested). These included Enterococcus, Candida parapsilosis, α-hemolytic Streptococcus, and Aureobasidium pullulans (Table 2). All were found in low concentration and only at 1 site and time point. One was isolated on day 0, 1 on day 7, 1 on day 14, and 1 on day 21 (Table 2).
      Table 2Potential pathogens
      MicrobeTotal positive culturesEndoscopeChannelDayConcentration
      Enterococcus1ColonoscopeBiopsy71 CFU/mL
      Candida parapsilosis1DuodenoscopeBiopsy211 CFU/mL
      α-Hemolytic Streptococcus1GastroscopeBiopsy14Thio broth only
      Thio broth only is considered to be <1 CFU/mL.
      Aureobasidium pullulans1ColonoscopeBiopsy11 CFU/mL
      CFU, Colony-forming unit.
      Thio broth only is considered to be <1 CFU/mL.
      The 4 potential pathogens were cultured from 2 colonoscopes, 1 duodenoscope, and 1 gastroscope, all from the biopsy channel (Table 2). This was also the most common site for all positive cultures (22 of the 33) (Table 3).
      Table 3Isolates by endoscope
      ScopeNo. of positive culturesBiopsy channelSuction channelElevatorDay 0Day 7Day 14Day 21
      C1330n/a0111
      C2321n/a1110
      C3541n/a1121
      C411000010
      D142111003
      D264110213
      D321010101
      D441211021
      G1110n/a0001
      G2431n/a0211
      Total33227448912
      C, Colonoscope; n/a, not applicable; D, duodenoscope; G, gastroscope.

      Discussion

      Exogenous transmission of infection via endoscopy is a rare event when proper high-level disinfection techniques are used, but the shelf-life before virulent microbial colonization may occur is not currently known. In this study, we provide evidence that a storage time of 21 days is likely safe.
      Our results are consistent with and complement those of previous reports. One study demonstrated no clinically significant growth on gastroscopes, colonoscopies, and duodenoscopes at 5 days.
      • Rejchrt S.
      • Cermak P.
      • Pavlatova L.
      • et al.
      Bacteriologic testing of endoscopes after high-level disinfection.
      Two reports evaluating colonoscopes alone demonstrated no clinically significant contamination at 7 days.
      • Riley R.
      • Beanland C.
      • Bos H.
      Establishing the shelf life of flexible colonoscopes.
      • Riley R.G.
      • Beanland C.J.
      • Polglase A.L.
      Extending the shelf-life of decontaminated flexible colonoscopes.
      A larger study involving 23 endoscopes, including gastroscopes, duodenoscopes, colonoscopies, and EUS endoscopes showed no potentially or true pathogenic microorganisms at 5 days, and only 1 (yeast) when incubation was extended to 7 days.
      • Osborne S.
      • Reynolds S.
      • George N.
      • et al.
      Challenging endoscopy reprocessing guidelines: a prospective study investigating the safe shelf life of flexible endoscopes in a tertiary gastroenterology unit.
      A study from 2007 recovered no pathogens or potential pathogens on 3 colonoscopes and 4 duodenoscopes at 14 days.
      • Vergis A.S.
      • Thomson D.
      • Pieroni P.
      • et al.
      Reprocessing flexible gastrointestinal endoscopies after a period of disuse: is it necessary?.
      A more recent study evaluated 4 colonoscopes over an 8-week period, finding no pathogens
      • Ingram J.
      • Gaines P.
      • Kite R.
      • et al.
      Evaluation of medically significant bacteria in colonoscopes after 8 weeks of shelf life in open air storage.
      ; however, this study was limited to colonoscopies, and fungal cultures were not obtained.
      In this study, we found a large number of positive cultures with nonpathogenic microbes. This is likely attributed to contamination while obtaining and/or inoculating samples and thus not clinically significant. We also identified 4 potential pathogens (Enterococcus, Candida parapsilosis, α-hemolytic Streptococcus, and A pullulans), although the clinical significance of these isolates is questionable because each was only identified at 1 time point and at 1 site (ie, not identified on repeated cultures from the same or different sites). Additionally, although no established clinically relevant bioburden has been reached, the growth rate in each instance fell well below the proposed threshold of 100 CFU/mL (3 cultures with 1 CFU/mL and 1 thio broth only).
      • Alfa M.J.
      • Sepehri S.
      • Olson N.
      • et al.
      Establishing a clinically relevant bioburden benchmark: a quality indicator for adequate reprocessing and storage of flexible gastrointestinal endoscopes.
      Moreover, none of these pathogens have been documented in any reported cases of endoscopic transmission of infection.
      • Kovaleva J.
      • Peters F.T.
      • van der Mei H.C.
      • et al.
      Transmission of infection by flexible gastrointestinal endoscopy and bronchoscopy.
      Finally, the random distribution of time points of these pathogens (0, 7, 14, and 21 days) makes them most likely contaminants given the previous studies demonstrating the low risk of potentially pathogenic species for as long as 8 weeks after reprocessing.
      • Riley R.
      • Beanland C.
      • Bos H.
      Establishing the shelf life of flexible colonoscopes.
      • Riley R.G.
      • Beanland C.J.
      • Polglase A.L.
      Extending the shelf-life of decontaminated flexible colonoscopes.
      • Rejchrt S.
      • Cermak P.
      • Pavlatova L.
      • et al.
      Bacteriologic testing of endoscopes after high-level disinfection.
      • Osborne S.
      • Reynolds S.
      • George N.
      • et al.
      Challenging endoscopy reprocessing guidelines: a prospective study investigating the safe shelf life of flexible endoscopes in a tertiary gastroenterology unit.
      • Vergis A.S.
      • Thomson D.
      • Pieroni P.
      • et al.
      Reprocessing flexible gastrointestinal endoscopies after a period of disuse: is it necessary?.
      • Ingram J.
      • Gaines P.
      • Kite R.
      • et al.
      Evaluation of medically significant bacteria in colonoscopes after 8 weeks of shelf life in open air storage.
      We elected to sample the endoscope channels but not the surface. It has been noted that the channels (particularly the biopsy channel) are the best means of assessing microbial colonization because they are more likely to harbor microorganisms than is the surface.
      • Chiu K.-W.
      • Tsai M.-C.
      • Wu K.-L.
      • et al.
      Surveillance cultures of samples from biopsy channels and automated endoscope reprocessors after high-level disinfection of gastrointestinal endoscopes.
      This is because of the lower accessibility of the channels to cleaning equipment, subsequent biofilm collection, as well as the increased damage incurred in these areas during use.
      • Chiu K.-W.
      • Tsai M.-C.
      • Wu K.-L.
      • et al.
      Surveillance cultures of samples from biopsy channels and automated endoscope reprocessors after high-level disinfection of gastrointestinal endoscopes.
      This is the first study that evaluates colonization of gastroscopes, colonoscopes, and duodenoscopes for as long as 21 days after reprocessing. Evidence is now accruing that we can safely shelve flexible endoscopes after standard disinfection for longer durations than are currently practiced. It is uncertain what the maximum duration is, but for now, extending beyond the 5 to 7 days that is practiced in many units could result in considerable cost savings. Specifically, less-frequent processing would decrease the amount of endoscopy staff time required, the use of disinfectants, and the use of processors. Additionally, less-frequent intervals may facilitate endoscopy unit throughput and minimize delays in procedures because of the lack of available endoscopes. Future studies with extended cultures beyond 21 days would be critical to understand the maximum shelf-life of flexible endoscopes after reprocessing.
      It should be emphasized that our conclusions and recommendations clearly apply only when endoscopes are reprocessed and stored in optimal fashion. It is conceivable that short shelf-times may occasionally have minimized the potential adverse effects of inadequate reprocessing at some centers and that lengthening the time in such circumstances could be detrimental. Finally, other similar studies are needed to assess whether the conclusions apply to other reprocessing systems and disinfection agents.

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      Linked Article

      • Method for assessing the microbial contamination of GI endoscopes
        Gastrointestinal EndoscopyVol. 82Issue 3
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          We read with interest the article regarding endoscope storage time after reprocessing.1 The statement suggested that endoscopes can be stored for as long as 21 days after standard reprocessing with low risk of pathogenic microbial colonization. Only 4 isolates represented potential pathogens (4.2% of 96 sites tested), and all were found in low concentrations. The authors’ results were consistent with those of previous studies that evaluated endoscope contamination using a similar method of sampling.
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