Emergence and local dissemination of NDM-14-producing Klebsiella pneumoniae ST147: a phylodynamic and epidemiological investigation.

NDM-14-producing Klebsiella pneumoniae ST147 has recently emerged as a high-risk clone in Europe, but its local dissemination dynamics remain poorly defined. We investigated a 6-month outbreak across three hospitals within a regional healthcare network in Lombardy, Northern Italy. Among 32 NDM-producing K. pneumoniae, isolated between December 2024 and May 2025, 19 belonged to ST147, including one NDM-1 producer and 18 carrying NDM-14 or its A233V variant NDM-61. Phylodynamic analysis of the ST147 NDM-14/NDM-61 genomes showed they were closely related (8-91 core SNPs) and descended from a most recent common ancestor dated to June 2024 (95% highest posterior density interval, 6 months). Reconstruction of the transmission network hints at the presence of at least three transmission clusters within the healthcare system: a major chain involving 11 of 18 cases spanning wards and facilities, a separate pair of linked cases, and 5 epidemiologically unlinked cases, suggesting missed intermediates or secondary introductions. The spread was characterized by rapid local expansion of the clone across intensive care, medical, and rehabilitation. These findings underscore the propensity of NDM-14-producing ST147 to disseminate efficiently within interconnected hospitals and highlight the need for enhanced genomic surveillance, coordinated infection control strategies, and judicious use of last-resort agents in regional healthcare networks. In a global phylogenetic context, the Italian isolates clustered within a broader NDM-14 ST147 population composed of several geographically distinct clades associated with France, Italy, Spain, Morocco, and the United Kingdom.