1a - Nosocomial outbreak of Ralstonia pickettii infections linked to sodium chloride in Germany since September 2023 and challenges in medical product-related outbreak investigations

Background : In December 2023, WHO reported a nosocomial outbreak of Ralstonia pickettii in Australia by contaminated sodium chloride-solution from an Indian manufacturer, causing bacteraemia. Concurrently, the Antibiotic Resistance Surveillance, a Germany-wide voluntary laboratory network, had captured five R. pickettii-positive blood cultures since September 2023 versus 0-1 annually in 2019-2022. This prompted an outbreak investigation to identify the infection source.

Methods : Case definition: A person with any material positive for R. pickettii (possible case). We implemented nationwide R. pickettii surveillance, performed Illumina whole genome-sequencing on isolates and core genome-multilocus sequence typing-based cluster detection (2499 target genes), and gathered case data, including common exposures to medical products.

Results : Since September 2023, we have detected 24 possible cases and could sequence 16 isolates. Six isolates clustered within a 3-allele difference, differing from Australian outbreak sequences by ≥26 alleles. These cases were considered confirmed cases and occurred in three hospitals across three federal states between 10/2023-3/2024. Five cases suffered from severe infection. Exposure to sodium chloride-solution was the only common link between all cases. Patient files did not specify the products. Hospital purchase lists did not generally specify supplied wards. Comparing hospital-level purchases, two products by two manufacturers matched across the three hospitals. Lot number lists from two hospitals revealed one match per product. The third hospital’s list is pending due to non-digitalized documentation. Sterility tests for both lots were requested from both manufacturers, with results still pending.

Conclusions : Surveillance in Germany sensitively detected an R. pickettii outbreak, possibly linked to sodium chloride-solution. Automated patient-level documentation of exposure to all medical product lots including saline solution and mandates for public retain sample testing could fasten identification of contaminated products in future outbreaks.