In light of recent large endoscope-related outbreaks in major academic medical centers, bronchoscope users must be aware of the difficulties presented by the presence of biofilm. Of all the contaminants commonly found on bronchoscopes, biofilm may be the most pernicious. Its accumulation contributes to the failure of cleaning and decontamination.
An authoritative study by Pajkos, Vickery and Cossart describes biofilm as “multi-layered bacterial or fungal cell clusters embedded in an amorphous extracellular material composed of exopolysaccharides of bacterial origin.”1 The problem is that the extracellular material cements cells firmly to the surface and to each other and thereafter defies cleaning.
Fortunately, biofilm is not impenetrable, according to Pajkos et al. It can be removed by physical or chemical means.
“However, the air/water channels of many endoscopes are too small to be cleaned mechanically and require cleaning solely by chemical means, and the chemicals used for removal of biofilm in industry are incompatible with the materials used in endoscopes,” they say.
To find out whether biofilm develops on the internal channels of endoscopes during routine use, Pajkos et al. studied 13 biopsy channels and 12 air/water channels from 13 used gastrointestinal endoscopes from 13 different hospitals in Australia.
Electron microscopy of the biopsy control channels showed that all had surface defects in the form of microscopic cracks, grooves and pits, some covered by biofilm.
Cleaning did not remove the contagion from smaller air and water channels. Pajkos et al. found microorganisms entrapped in soil, in one case with extensive biofilm formation. Healthy bacterial cells were overlaid by exopolysaccharide and soil, shielding microorganisms from the damaging effects of disinfectants. Brushing removed a majority of the soil, but microscopic deposits were still seen in patches.
Pajkos et al. postulated that biofilm could prevent germicide from penetrating, and could inactivate disinfectants.
“Even rigorous cleaning with detergent and brushing, and disinfection with 2% glutaraldehyde followed by rinsing with 70% alcohol and forced-air drying left positive cultures in 18% of endoscopes tested (11 of 60 instruments).” Pajkos et al. concluded that current cleaning and disinfection processing of endoscopes are inadequate, and that damage to the lining by accessory instruments contributes significantly to soil accumulation. The authors also suggested that endoscopes be redesigned.
Once a biofilm forms, it is almost impossible to eradicate. With current cleaning and disinfection processing and limitations in the current design of endoscopes, maintaining the status quo may not be enough to ensure patient safety. For clinicians who are serious about preventing biofilm contamination, the option of disposable or single-use bronschoscopes (Ambu) offers a unique opportunity to avoid the risks associated with biofilm accumulation.
1. “Is biofilm accumulation on endoscope tubing a contributor to the failure of cleaning and decontamination?” J Hosp Infect 2004