Standardising the Efficacy Testing of Reprocessing Procedures for Semi- Critical Medical Devices. A Case Study Using UV-C Chambers for Ultrasound Probes

FHH Brill, A Ulatowski, H Gabriel, K Walendy-Gnirß

Infection Prevention 2026 (IP 2026) | poster presentation by Dr Florian H. H. Brill | Leeds, UK, 28 - 29 September 2026

Introduction: Reusable semi-critical medical devices such as ultrasound probes and endoscopes require effective reprocessing to prevent healthcare-associated infections. Traditional applications include wiping, soaking, and washer-disinfectors, but recently UV-C-based disinfection is used for this purpose. Despite its growing use, efficacy test standards have not kept pace with these advances, and applicability of EN 14885 standards for chemical disinfectants is questionable, creating an unclear efficacy evaluation for UV-C performance under practical conditions, with particular focus on oxidative disinfectants, especially peracetic acid–based formulations.

Method: We propose a novel method for assessing UV-C disinfection chambers using clinically relevant microorganisms specified in EN 14885, EN 16615, and EN 17846: the bacterium Staphylococcus aureus, bacterial spores of Clostridioides difficile, the yeast Candidozyma auris and the fungus Aspergillus brasiliensis, plus UV resistant species Micrococcus luteus and Acinetobacter radioresistens. A new carrier was selected based on size, shape, and material of target devices, providing a realistic challenge. The contamination method and acceptance criteria were aligned with EN 16615 and EN 17846 phase 2 tests for chemical surface disinfectants. isolates representing different phylogenetic clades were included to assess clade-dependent susceptibility differences.

Results: Testing demonstrated the method achieved acceptable recovery and quantification of log reductions per EN standards. Manual disinfection achieved a significantly greater reduction in S. aureus compared with UV-C disinfection (Mann Whitney U test, p = 0.0045,**).

Conclusion:

• The UV-C disinfection chamber evaluated did not meet the required acceptance criteria for all tested microorganisms
• It achieved 2 - 3 log10 reduction, indicating insufficient microbial reduction under realistic conditions.
• These findings suggest that UV-C, despite its broad antimicrobial activity, requires practice-like qualification ensuring correct application conditions (time and dose)
• Development of a dedicated standard defining test criteria for UV-C devices is critical for patient safety may therefore refine efficacy testing in selected scenarios.