Gastroscope processing in washer–disinfectors at three different temperatures

Abstract

Endoscopes are processed chemo-thermally at approximately 56 °C in washer–disinfectors in Germany. In this study we investigated the processing of gastroscopes by an endoscope washer–disinfector at different temperatures. A total of 87 gastroscopes were tested hygienically and microbiologically before manual cleaning (after patient use), as well as after manual cleaning and after endoscope washer–disinfector processing at running temperatures of 43, 51 and 56 °C. In all tests the suction/biopsy channels of the gastroscopes were flushed with 50 mL sterile solution throughout their full length, from the proximal to the distal ends. The rinse solutions were plated on to various culture media. Also, in order to detect low bacterial counts, 3×10 mL rinse solution was membrane filtrated. The German guideline level for total bacterial counts, applicable since 2002, was exceeded at all temperatures tested (159 cfu/mL at 43 °C, <60 cfu/mL at 51 °C, and 8 cfu/mL at 56 °C). A temperature increase from 43 to 51 °C resulted in a highly significant reduction of the residual contamination by aerobic bacteria ( P<0.001, Mann–Whitney U Test), Gram-negative bacilli ( P<0.001), and pseudomonads ( P=0.002). A further temperature increase from 51 to 56 °C resulted in a further highly significant drop in residual contamination by aerobic bacteria ( P=0.021) and pseudomonads ( P=0.036). The aim of the user—minimizing material damage to endoscopes or prolonging their product life—cannot be achieved through lowering the processing temperature without putting patients at risk. In order to ensure adequate processing, endoscope washer–disinfectors should meet the requirements of current draft standards.