Ultrasound endoscopes and routine microbiological surveillance - another critical device in reprocessing

Periodic routine microbiological surveillance of gastrointestinal endoscopes is recommended to ensure adequacy of reprocessing.

To investigate whether there were differences in contamination depending on the type of endoscope.

A total of 437 microbiological surveillance samples obtained from gastrointestinal endoscopes at a tertiary-care centre in Switzerland were analysed. Sampling was performed after reprocessing in washer-disinfectors according to Standard SN EN ISO 15883-4:2018. For microbiological analysis, endoscope irrigation solution was filtered and transferred to sheep blood agar. These plates were incubated at 37 °C. If bacterial growth was detected, the species was identified using matrix-assisted laser desorption-ionization time-of-flight mass spectrometry or other microbiological identification techniques, and colony-forming units (cfu) were counted. Contamination was defined as detection of any micro-organism with ≥20 cfu/20 mL or detection of Enterobacterales, Enterococcus spp., Pseudomonas aeruginosa and other non-fermenters, Streptococcus viridans and Staphylococcus aureus, independent of cfu count.

In total, 204 samples were gathered from 28 gastroscopes, 146 samples from 23 colonoscopes, 45 samples from five ultrasound endoscopes, 27 from four duodenoscopes and 15 from three enteroscopes, respectively. Eleven (2.5%) samples, gathered from five endoscopes, indicated contamination. The proportion of samples indicating contamination varied largely by endoscope type: 20.0% (9/45) of ultrasound endoscope-derived, 1.4% (2/146) of colonoscope-derived, 0.5% (1/204) of gastroscope-derived, 0% (0/27) of duodenoscope-derived, and 0% (0/15) of enteroscope-derived samples were contaminated (P < 0.001).

Overall, a small proportion of endoscopes were contaminated. Significant differences were observed based on the type of endoscope, with ultrasound endoscopes performing worst.