Comprehensive review of how endoscope channel biofilm differs from hydrated and dry surface biofilm and its implications

Background and Study aims: Flexible endoscope related infection outbreaks related to biofilm in endoscope channels continue to be reported. This article reviews how endoscope fixed-biofilm accumulation (EFBA) develops in flexible endoscope channels over repeated clinical uses. The aim of this review is to highlight how EFBA differs from dry surface biofilm (DSB) and hydrated biofilm (HB). Patients/Materials and methods: The process of (EFBA) formation in patient used endoscope channels is compared to that of DSB and HB. The inadequate (or lack) of cleaning in narrow endoscope channels and the impact of High Level Disinfection (HLD) fixing the EFBA within endoscope channels results in a very different matrix compared to DSB or HB. The impact of fixed EFBA on microorganism survival within the matrix provides a more stringent and realistic challenge compared to DSB or HB. The choice of an appropriate multi-species biofilm model is also crucial to ensuring it closely mirrors the clinical aspects related to EFBA. Results: This comprehensive review confirms that EFBA is a driver of persistent endoscope channel contamination and exogenous transfer of pathogens to patients that can lead to infection. The literature review demonstrates that mono-microbic HB is the most common biofilm model used over the past 20 years whereas models that integrate rounds of fixation such as the endoscope cyclic buildup biofilm (ECBB) and endoscope buildup biofilm (EBBF) better reflect the clinical aspects of EFBA in patient-used endoscope channels. Conclusions: The published data supports the need to use an appropriate fixed-biofilm model when validating cleaning and disinfection processes for flexible endoscope channels thereby ensuring an optimal margin of safety during clinical use.