There's nothing new about the required steps of high-level disinfection: manual brushing of flexible endoscope channels with enzymatic detergent, flushing with sterile water and a run through an automatic reprocessor. But recent studies have shown that more attention must be paid to the small details of the process in order to prevent bacteria from forming in complex devices that are already exceedingly difficult to clean and disinfect.
A study in BMC Gastroenterology (tinyurl.com/pdff7f2) points out the channels of endoscopes can be "heavily contaminated" with bacteria, even after high-level disinfection is performed. The researchers tested the efficacy of manual brushing and automatic endoscope reprocessors (AERs) in disinfecting biopsy channels by collecting 420 samples of sterile distilled water flushed through channels of gastroscopes and colonoscopes and swabbing residual water from AERs after full reprocessing cycles were run.
According to the study, 13.6% of the biopsy channel samples and 1.7% of AER samples were culture-positive. Specifically, 10.7% of the 300 samples taken from gastroscopes and 20.8% of the 120 samples taken from colonoscopes were culture-positive; both were significantly higher than the positive cultures obtained from the AERs used to reprocess them: 2% and 0.8%, respectively.
The researchers say endoscopes are complex instruments that are difficult to clean and reprocess effectively, and note that colonoscopes were more contaminated than gastroscopes in their study. Interestingly, the researchers say the number of culture-positive samples obtained from colonoscopes was two times higher than those obtained from gastroscopes, which the researchers say spotlights the importance of proper colonoscope reprocessing.
They say the inner surfaces of biopsy channels might not be fully decontaminated, even after a full reprocessing cycle, which highlights the importance of regularly monitoring the quality of endoscope reprocessing. (More on that later.)
A study published in the journal BMC Infectious Diseases (tinyurl.com/ornl2m5) suggests biofilm builds up over time in the channels of flexible endoscopes because of the constant exposure to the wet and dry phases of reprocessing cycles. Between 40% and 50% of patients treated with contaminated scopes will become colonized, according to study co-author Michelle J. Alfa, PhD, FCCM, the principal investigator at the St. Boniface Research Centre in Winnipeg, Manitoba, Canada. Her study notes that as flexible endoscopes are repeatedly used and reprocessed, the load of biofilm increases, as does the risk of transmission of pathogens.
After the final rinse of the reprocessing cycle, advises Dr. Alfa, wipe down endoscopes' exteriors, its valves and attachments with a lint-free cloth, purge channels with 70% to 80% isopropyl alcohol followed by forced air to ensure channel drying, and hang scopes in storage with the valves removed so the internal channels remain dry. She says properly storing endoscopes dry and hanging keeps moisture from remaining in channels, which prevents bacteria from replicating and, ultimately, biofilm from forming.
Her study shows that a wide range of microorganisms develop in built up biofilm and accumulate more rapidly, compared with traditional biofilm that forms when surfaces are bathed in fluid, a finding that's more prevalent when glutaraldehyde is used to reprocess endoscopes instead of accelerated hydrogen peroxide (AHP). High-level disinfection with glutaraldehyde is less effective than AHP for killing microorganisms in either traditional or built up biofilm, says the study, which suggests potentially harmful organisms stand a greater chance of survival if biofilm is permitted to build up in endoscope channels.
The 'Achilles' Heel' of Infection Prevention
Endoscope reprocessing is a fragile process in how intensely it relies on frontline staff to properly complete multiple steps, says Bret T. Petersen, MD, professor of medicine at the Mayo Clinic in Rochester, Minn., and a national expert on high-level disinfection.
"It's subject to lapses, depending on the pace of given units, a given day or a given staff member," he adds. "We're all highly attuned to that reality being a bit of an Achilles' heel in the process of infection control."
There have been a couple clusters that have received increased scrutiny in recent months, particularly related to endoscopic retrograde cholangiopancreatography (ERCP). Last January, the CDC issued a report (tinyurl.com/pusk92q) about the 9 patients who were infected by a new strain of New Delhi metallo-??-lactamase after undergoing endoscopic retrograde cholangiopancreatography. Cultures taken from the flexible endoscope used on 5 of the patients after it underwent high-level disinfection turned up NDM-producing E. coli in the scope's elevator channel, the strain that was linked to the outbreak. The CDC says the ERCP endoscope's complex design makes cleaning and disinfection a challenge.
"The outbreaks in the ECRP arena have come to our attention almost fortuitously, because they happen to involve a bug that gets reported up the chain of awareness to health departments, epidemiologists and, ultimately, to the CDC," says Dr. Petersen.
But it begs the question: Are outbreaks, however minor, happening more often than is known? Perhaps. "We just don't have the red flag of the rare bug of multidrug-resistant organisms to bring it to our attention," says Dr. Petersen.
He believes there's been a recent shift in how experts view high-level disinfection. Is it a major issue? And if it is, how common are reprocessing problems at the front line?
Until prospective studies provide the answers, Dr. Petersen believes national organizations need to collaborate on standardizing and intensifying education surrounding endoscope reprocessing and the competency testing used to test staff performances.
Even though multi-societal recommendations establish endoscope reprocessing as a standardized process, is it being instructed and performed the same way in every facility? "There's a realization that it'd be very beneficial to tighten up the specifics of the process how it's taught, how it's monitored and how competency is assessed even if doing so relies on existing guidelines," says Dr. Petersen.
He's had recent conversations with national experts and clinical staff who want to establish GI-specific credentials for high-level disinfection. It's a realistic goal, he says, but one that will take a few years to implement, even if all interested parties agree to move forward with credentialing efforts.
In the meantime, facilities need to maintain heightened awareness of proper high-level disinfection. "We're more attuned to the importance of endoscope reprocessing now than a couple years ago," says Dr. Petersen, "even though we've always been aware that we need to be diligent."
Adenosine triphosphate (ATP) tests detect contamination that remains in endoscope channels, indicating the instruments need to re-cleaned before undergoing automatic reprocessing.
Dr. Alfa co-authored a study in the American Journal of Infection Control (tinyurl.com/puc5ohb) that showed 96% of 120 channels in 20 colonoscopes and 20 duodenoscopes at a busy GI center met the acceptable ATP benchmark (less than 200 relative light units). Five out of the 120 channels that did not meet the benchmark were elevator guide-wire channels, notes the study, which concludes that nearly all of the endoscopes cleaned according to manufacturers' directions met acceptable clean benchmarks of the ATP test. That suggests the test is an effective and reliable way to audit the performance of endoscope reprocessing staffs.
Results of ATP tests are available in a matter of minutes, which means they provide real-time feedback on endoscope cleaning before automated high-level disinfection. Has the manual cleaning reduced bioburden enough, or would levels render high-level disinfection ineffective? The tests might be best applied to spot-check individual scopes or to test the performance of new staff during orientation or veterans during quarterly competencies.
Failure at the front line
A study in the journal Infection Control and Hospital Epidemiology (tinyurl.com/nkrxgzk) notes that many endoscopy-associated outbreaks are related to breaches in reprocessing techniques, and says it's imperative that cleaning and disinfection be performed correctly. The study's authors also point out that AERs offer several advantages over manual reprocessing, including the automation and standardization of reprocessing steps.
The study says the incidence of endoscope-associated infection, while generally underreported, is very low: approximately 1 in 1.8 million procedures. Most outbreaks involve waterborne or enteric bacteria, including Pseudomonas, Salmonella, and Mycobacteria species.
A report in the journal Clinical Infectious Diseases (tinyurl.com/pzcmeej) says that although the incidence of infection linked to endoscope use is exceedingly low, the instruments have been linked to infection outbreaks more than any other medical device.
The recommendations for proper endoscope reprocessing are clear clean, disinfect, rinse, dry and store but the study says audits have shown reprocessing staff still fail to follow these simple tenets and resulting outbreaks still occur.