Study On The Removal Efficacy Of Flexible Endoscope Cleaning Brushes On Endoscopic Biofilm

ObjectiveEndoscopes are prone to formation of bacterial biofilms which protect bacteria from environmental influences and increase bacterial resistance to the reprocessing procedures. The presence of biofilm may result in nosocomial infections due to sterilization failure Endoscopic biofilm formation can thus threaten patient safety leading various authorities and associations to issued guideline and standards regarding endoscopic cleaning and disinfection and infection control. In addition, the general public has shown increasing attention and concern about endoscopic sterialization.According to the researches by western countries, the incidence of biofilm in suction/biopsy endoscopic channels ranged from38%to42%. However, the figures could not be independently confirmed in China mainland yet. Its composition is influenced and determined by multiple factors which include both the using and reprocessing procedures. A mass of guidelines and standards were published by endoscopic academic institutions, but seldomly is of concern to the prevention and elimination of endoscopic biofilm.Biofilm can be removed by chemical or physical means and there are many different detergent products available in the market which contain enzymes to assist in biofilm removal. However there are disadvantages in using detergent products include occupational injuries, cleaning process chemicals remaining on the endoscopes, and environmental contamination with the chemicals. Furthermore, chemical means may be less effective whenever biofilms are present as bacteria within the biofilm matrix are up to1,000times more resistant to antimicrobials than the same bacteria in suspension.Brushing has been shown to be reasonably effective in biofilm removal. A number of different types of endoscope cleaning brushes are available commercially but to date no studies have been published showing their comparative effectiveness in terms of biofilm removal. Manual cleaning procedures generally includes brushing of the interior channels. The lack of comparative studies requires the endoscopic staff exhibit considerable arbitrariness when choosing which brush device or devices to use as well as the duration of brushing and the number of brushings to routinely perform. The choice of brushes and brushing times must also be balanced between effectiveness vs. possible damage to the endoscope during the reprocessing procedures.Basing on our early stage research work, the study is conducted to investigate and collect10biopsy channels from10used gastrointestinal endoscopes were obtained from10different endoscope-servicing departments of top-level hospitals in China. Then in vitro study aimed to evaluate and compare the removal effectiveness of different endoscopic cleaning brushes and times which are commonly used in endoscopic reprocessing procedure against Escherichia coli biofilm on endoscopic lumen. MethodsThe endoscopes were of various ages. All endoscopes arrived at the endoscope-servicing centre with documented evidence of decontamination. A2-cm segment of tubing was removed approximately10-cm from the tip of each endoscope. Each piece of tubing was then cut in quarter longitudinally and opened out flat. The entire internal surface of the tube could then be examined by scanning electron microscopy (SEM). All the SEM test tube sections with planktonic bacteria were rinsed and placed in a2.5%glutaraldehyde fixation solution at4℃for2hours and then rinsed with PBS (pH=7.2), dehydrated with acetone, isoamyl acetate replacement, CO2critical point drying and gold coating by ion spray. The specimens were then examined systematically using a Hitachi S-3000N SEM. Photographs of representative areas were taken.Every device was sterile before use. Escherichia coli biofilm was generated on160cm endoscopic lumens under low flow conditions for10days. The tube was cut into2cm sections to prepare a total of48specimens. Specimens were washed in sterile phosphate buffered saline solution3times to remove any planktonic bacteria and then randomly separated into different lumen-cleaning devices. Each device was further separated into groups with designated brushing times of once, twice, and three times totaling12groups.Each4test specimens (3for viable bacteria count,1for SEM) were immersed in PBS solution container flushed or blushed together once, twice, or three times. After the brushing step, the tubes were further immersed in PBS solution to wash away remaining planktonic bacteria. The biofilm viable count was performed as viable bacteria counts and the biofilm residual was observed by SEM with the same method used for the10biopsy channels. The above procedures were repeated4times.The above-mentioned treated tube sections were split longitudinally and scored with a2-mm-wide sterile wooden stick. The section and stick were placed together in a sterile test tube with5mL of PBS, immersed in an ultrasonic bath, shaken for10min (42-47KH,20℃), and then vortex shaken for2minutes. Serial10-fold dilutions were made. Appropriate dilutions seeded onto sterile Petri dishes with15mL of45℃M-H agar, and incubated at37℃for24hours. Colonies were counted on all dishes with colony numbers between30and300CFU. The result was calculated per square centimetre (CFU/cm2) of the internal surface area of the tubing. The logarithm of the actual colony count (1gCFU/cm2) was the standard colony count.ResultsThe time-use data show that10endoscopes were using from0.5to9years. All10suction/biopsy endoscopic channels examined showed varying degrees of damaged surface. From SEM observation illustrated that inner surfaces were scuffed, scrubbed and split. Biofilm existed in7of10suction/biopsy endoscopic channels, and this was extensive on3samples. At high magnification, the numerous bacteria and soiling adhered to the inner surface and were enshrouded by EPS. It is particularly evident in the damaged sites.For all the10corresponding hospitals, disinfecting cleaning methods are varied.100%of the departments are using the reusable wire brush, but the brushing water and brushing frequencies are different.90%departments reuse the disposable therapeutic devices, and30%can not replace brushes in time. The action time of detergent and disinfectant and the rinsing time are not the same either.As for the results of in vitro study, the control tubing group had14.631gCFU/cm2. Wire brush, wiper brush and sponge brush the results were3.36,1.62and10.221gCFU/cm2respectively such that the wiper brush resulted in greater than a13log reduction, whereas the sponge brush resulted in only a4log reduction. The stiff wire brush resulted in a11log reduction in1gCFU/cm2. The results of different brushing frequencies for once, twice or three times were8.32,7.00and7.061gCFU/cm2respectively.The between-subjects effects (P=0.042) were found in two variables:brush device and brushing times. Overall significant differences in residual biofilm bacteria were observed among the different brush devices and number of brushings (P<0.05). Therefore, separate estimates of the effect of each variable were obtained. Multiple comparisons showed that significant differences existed between control group and three brush groups (P<0.001). The other variable (i.e. number of times brushed) showed that brushing twice resulted in a significant reduction in viable bacteria compared to brushing only once (P=0.004) but that there was no significant difference between brushing two or three times (P=0.893).After a continuous perfusion of10days, SEM showed a solid mature biofilm structure embedded evenly over the surface by a large extracellular matrix. On the inner surface of post treatment tubes from all groups, the remaining biofilm was scanned by SEM. SEM examination of the tubing of control group showed a continuous multilayered biofilm as the pre treatment tubing, consisting of many bacterial cells cemented in EPS and covering the entire internal surface. There were minimal visible differences among three different flushing frequencies such that most of the biofilm bacteria retained their morphological integrity.Post brushing, a comb-like residual of bacteria were observed on low power field after the stiff wire brush reacted for different frequencies. The amount of residual biofilm matrix and scattered cell debris remaining diminished gradually as the number of brushings increased. With the wiper brush a few of E. coli with some debris remained when viewed under high power. However, the residual biofilm in sponge brush was clearly greater than with the other two brushes as a thick residue was observed and bacteria with morphological integrity remained.ConclusionsThis study found evidence that microscopic damage to the endoscope lining permits the accumulation of soil. The presence of soil and biofilms suggests that current cleaning and disinfection processing of endoscopes are inadequate. The presence of surface defects appears to promote accumulation of micro-organisms and soil. Damage to the lining by accessory instruments contributes significantly to soil accumulation. More efficacious cleaning methods and agents are required to remove soil and biofilm from endoscope surface.Previous studies have shown that mechanical friction is the most efficient way of reducing biofilm and eliminating potentially harmful microorganisms. We found that all three different types of cleaning brush resulted in removal of biofilm to some degree. It is critical that any guidelines must emphasize that manual cleaning is a critical part of the endoscope cleaning and disinfection process as only mechanical cleaning can prevent residues in the interior channels from remaining after the disinfection process and thus promote the formation of biofilms.Brushing twice appeared to be adequate and reducing the brushing from3to2also reduced processing times by at least1min making it the most effective strategy.In our study the wiper brush was marginally superior to the stiff wire brush and both were superior to the sponge brush. The sponge brush was unsatisfactory for mechanically reducing the adherent biofilm’s bacterial cells most likely because the sponge was too soft to provide an adequate shearing force and friction to physically remove the biofilm. Whether the sponge brush with the impregnated detergent would have been effective was not examined. One possible advantage of the wiper brush was that it was used with a pull-through motion instead of the backwards and forwards motion required with the other brushes. The bristle stiff wire brush has a brush-like head which contained many slender crevices and a plastic ring short brush that did not completely make contact with the lumen wall possibly resulting in the SEM pattern showing a residual biofilm of comb-like extracellular matrix. Possibly, the design can be improved.Importantly, the size and type of cleaning brush must be matched appropriately to the size and type of endoscope channels, to ensure contact with channel walls. To ensure maximum effectiveness of cleaning and to avoid tissue carryover, both the ESGE and the ESGENA recommend single-use brushes as these have undamaged bristles and cannot have any tissue remnants from previous examinations. Reusable brushes must be thoroughly cleaned manually, followed by ultrasonic cleaning and decontamination (preferably sterilization) after each usage which is at best difficult. The wiper brush is designed to be disposable which gives it an advantage of reusable brushes in elimination of reprocessing times and costs and the potential for cross-infection associated with cleaning and sterilizing brushes.Although appropriate manual brushing procedure can remove most of the biofilm, incorrect use and irregular replacement of brushes may result in scratches on the luminal surface of the endoscopes which would provides an ideal environment for biofilm. The adjunct use of a low corrosive chemical detergent and brushing may provide the best results for prevention and removal of biofilm and require further study.