Abstract
Efficient removal of biofilms from medical devices is a big challenge in health care to avoid hospital-acquired infections, especially from delicate devices like flexible endoscopes, which cannot be reprocessed using harsh chemicals or high temperatures. Therefore, milder solutions such as enzymatic cleaners have to be used, which need to be carefully developed to ensure efficacious performance. In vitro biofilm in a 96-well-plate system was used to select and optimize the formulation of novel enzymatic cleaners. Removal of the biofilm was quantified by crystal violet staining, while the disinfecting properties were evaluated by a BacTiter-Glo assay. The biofilm removal efficacy of the selected cleaner was further tested by using European standard (EN) for endoscope cleaning EN ISO 15883, and removal of artificial blood soil was investigated by treating TOSI (Test Object Surgical Instrument) cleaning indicators. Using the process described here, a novel enzymatic endoscope cleaner was developed, which removed 95% of Staphylococcus aureus and 90% of Pseudomonas aeruginosa biofilms in the 96-well plate system. With a >99% reduction of CFU and a >90% reduction of extracellular polymeric substances, this cleaner enabled subsequent complete disinfection and fulfilled acceptance criteria of EN ISO 15883. Furthermore, it efficiently removed blood soil and significantly outperformed comparable commercial products. The cleaning performance was stable even after storage of the cleaner for 6 months. It was demonstrated that incorporation of appropriate enzymes into the cleaner enhanced performance significantly.
Highlights
Efficient removal of biofilms from medical devices is a big challenge in health care to avoid hospital-acquired infections, especially from delicate devices like flexible endoscopes, which cannot be reprocessed using harsh chemicals or high temperatures
The use of S. aureus as a model microorganism is not appropriate for the selection of a base formulation since the bacteria found on endoscopes include many other species [3], of which, for example, the predominant species P. aeruginosa could not be removed with only protease [21]
For total biofilm biomass assessment, the results of optical density, protein, and polysaccharide quantification with the ISO test correlated with the results of crystal violet staining in the 96-well-plate assay, while for viable bacteria, the CFU corresponded to those determined by the BacTiter-Glo assay
Summary
Efficient removal of biofilms from medical devices is a big challenge in health care to avoid hospital-acquired infections, especially from delicate devices like flexible endoscopes, which cannot be reprocessed using harsh chemicals or high temperatures. Milder solutions such as enzymatic cleaners have to be used, which need to be carefully developed to ensure efficacious performance. One effective approach is to destabilize the biofilm EPS, which contain proteins, polysaccharides, lipids, extracellular DNA, and other substances Some enzymes such as protease [12, 13], DNase I [12, 14], alginate lyase [15, 16], amylase [13, 17], and cellulase [18, 19] have been reported to support biofilm removal. A new cleaner (deconex Prozyme Active) containing four enzymes in a novel base formulation was developed and appeared to perform better than nine comparable commercial products
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