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

BACKGROUNDCarbapenemase-producing Enterobacterales (CPE) cause infections, particularly nosocomially, with limited treatment options. NDM-1-producing <i>Klebsiella pneumoniae</i> cases have substantially increased since 2022, associated with the Ukraine war.AIMWe aimed to investigate transmission patterns using Germany's Integrated Genomic Surveillance (IGS), combining notifications and sequence data.METHODSWe selected NDM-1-producing <i>K. pneumoniae</i> 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.RESULTSAmong 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.CONCLUSIONMost 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.