International spread or local outbreak? Epidemiologic analyses of transmission patterns of NDM-1-producing Klebsiella pneumoniae based on genomic surveillance data, Germany, January 2022 to February 2023

BACKGROUND Carbapenemase-producing Enterobacterales (CPE) cause infections, particularly nosocomially, with limited treatment options. NDM-1-producing Klebsiella pneumoniae cases have substantially increased since 2022, associated with the Ukraine war. AIM We aimed to investigate transmission patterns using Germany’s Integrated Genomic Surveillance (IGS), combining notifications and sequence data. METHODS We selected NDM-1-producing K. pneumoniae cases, confirmed by isolates between 1 January 2022 and 28 February 2023. Isolates were Illumina whole genome-sequenced and linked to notifications. Clusters were defined as ≤ 12 allelic differences in core genome-wide single nucleotide variant-based genotyping. Cluster categories were: ‘no exposure abroad’, ‘exposure in Ukraine’ or ‘other exposure abroad’ if ≥ one case stayed in Ukraine or elsewhere. Follow-up of 13 clusters examined further exposure information. RESULTS Among 424 cases of most frequent sequence types, 326 (77%) belonged to 61 clusters. Seventeen (28%) clusters were associated with no exposure abroad, 33 (54%) with exposure in Ukraine, seven (11%) with other exposure abroad, and four (7%) had insufficient data. Cases in clusters with exposure in Ukraine were more dispersed, younger, and more often wound-infected than in other exposure location categories (p < 0.01). Cluster follow-up revealed one cluster with all cases from Ukraine or Russia, another with nosocomial transmission following case importation, and a third with all cases from one German hospital without exposure abroad. CONCLUSION Most cases were in clusters, suggesting preventable chains of transmission. Three patterns emerged: transmission abroad, transmission in German hospitals from imported cases or local outbreaks. IGS can identify where transmission could be interrupted. International cooperation needs strengthening to prevent CPE spread.