Transmission of infection by flexible endoscopy
Release of disease by flexible endoscopy
Flexible endoscopic procedures are used for diagnostic (i.e., visualization and sample collection) as well as therapeutic purposes for lungs, the esophagus, stomach and intestine , the biliary tract and pancreas , or the large bowel . Also, included are new modalities that continue to develop and evolve such as combined ultrasound transduodenoscopy, that gives endoscopic ultrasound to endoscopy .
Infections related to flexible endoscopic procedures are caused by either endogenous flora (the patient’s own microorganisms) or exogenous microbes (microorganisms introduced into the patient via the flexible endoscope and/or its accessories). The post-procedure infection rate related to inadequate reprocessing is difficult to manage, as there is no proposed research that a differentiate endogenously from exogenous infections.
Endogenous infections after flexible endoscopic procedures occur when the patient’s own microbial flora gain entry to the bloodstream or other normally sterile body sites as a result of mucosal trauma or instrumentation and are not related to instrument reprocessing problems e.g. pneumonia resulting from aspiration of oral secretions in a sedated patient or bacteremia resulting from microscopic tissue trauma occurring during endoscope insertion or removal.
Exogenous infections result from microorganisms introduced into the patient’s body by the flexible endoscope or the accessories used in the procedure. Such infections are preventable with strict adherence to accepted reprocessing guidelines. it may originate from:
An earlier practiced endoscope, followed by inadequate cleaning and/or improper reprocessing technique.
Contamination of the endoscope — associates, or automatic endoscope reprocessor from the environment during reprocessing —.
The reservoir for exogenous microorganisms within a flexible endoscope may be the suction/biopsy channel or any other channel in the flexible endoscope (e.g., elevator wire channel in side-viewing duodenoscopes, water/air channel inside the colonoscopes, or other auxiliary channels that can be present), the water bottle and tubing used for endoscopy procedures may also form a reservoir for exogenous microorganisms if these accessories are not properly reprocessed. Components of the reprocessing procedure itself may serve as a reservoir, such as cleaning brushes if non- examined, washed, and high level disinfected after each use; tap water diluted enzymatic detergent and tap water rinse that are not changed following each application, or if the water filtration operation is not sustained as per manufacturers’ instruction. Enzymatic detergent and rinse water used during manual cleaning should be changed for each scope to ensure residual microorganisms are not introduced into the next endoscope that is immersed in the used solution. Diluted enzymatic detergents should never be stored overnight as tap water-derived microorganisms can multiply to unacceptably high levels.
Tap water used for the last rinse after disinfection/sterilization may result in water microorganisms being left in the channels.
Transmissible spongiform encephalopathies (TSEs) are created by prions, that are protein particles that carry no nucleic acid, however, are able of creating a transmissible disease. All prions can remain infectious for years in a dry situation, and hold all regular sterilization and disinfection methods commonly used by healthcare facilities.
Disinfection techniques to eliminate prion infectivity include prolonged steam sterilization and extended soaks in concentrated sodium hydroxide, sodium hypochlorite, or formic acid. Unfortunately, an endoscope cannot be reprocessed by any of these procedures without sustaining severe damage. Therefore, endoscopes used on patients with vCJD must be single use or destroyed after use.
The chance of release of any pathogen from an endoscope depends on many factors including the susceptibility of the exposed individual, the infectivity load of the tissues, the amount of contaminating a tissue and the effectiveness of the decontamination processes.
Circumstances That Add to Survival of Microorganisms in Reprocessed Flexible Endoscopes
Bacteria may replicate to substantive levels even after overnight storage at room temperature if there is sufficient moisture in the endoscope channels. Some bacteria can survive drying (e.g., M. tuberculosis and Gram positive bacteria) whereas others, like Gram negative bacteria (e.g., P. aeruginosa plus E. coli), decay quickly when dried. Gram negative bacteria replicate more easily in the presence of moisture and have been implicated in endoscope associated infections more frequently than have Gram positive bacteria.
Humidity kept in the channels of flexible endoscopes is a major contributing factor to exogenous microorganisms being transmitted by flexible endoscopes and outbreaks related to inadequate drying and improper storage have been reported
Biofilm Formation and Organic Debris
Biofilms is an important part in their potential to cause endoscopy-related infections. During clinical use blood, excretions, mucus, plus another biological materials can adhere to the endoscope and its channels. If the channels are not well washed, there may be high remaining levels of organic material and microorganisms. If the endoscope remains moist for extended times, the remaining bacteria can reproduce biofilm. Microorganisms embedded within this biofilm are sheltered from the cidal activity of the disinfectant/sterilant. This assurance is moreover improved if there is residual organic material post-cleaning; subsequent exposure to aldehyde based disinfectants leads to fixation of the matrix, although the microorganisms inside the matrix (i.e., biofilm and/or residual patient secretions) may or may not be adequately killed. Additionally, biofilm formation explains why flexible endoscopes should not be left soaking in enzymatic soap overnight. Enzymatic soaps do not inhibit bacterial replication, and surely, the microorganisms can apply the enzyme proteins as an energy source. Therefore, the important step in endoscope reprocessing is bedside flushing, with following hand-operated cleaning and brushing of endoscope channels, as soon as possible after the procedure.
Equipment Design Flaws
Design flaws can contribute to if no promote microbial pollution despite adherence to proper reprocessing protocols. If the design flaw was a faulty biopsy port in a bronchoscope that could loosen, permitting patient secretions and microorganisms to become sequestered in a humid atmosphere, difficult to enough cleaning and disinfection.
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