Genomic surveillance in northern Portugal identified an expansion of carbapenemase-producing Klebsiella pneumoniae ST15-KL19 after the COVID-19 pandemic, rising from 23% to 35% while displacing the previously dominant ST147-KL64 strain. The shift highlights how dominant resistance lineages can change during periods of healthcare disruption. The finding matters for hospital infection-control programs because it reinforces the need for local, sequence-informed tracking rather than relying solely on phenotypic susceptibility trends. It also provides a concrete example of how antimicrobial resistance epidemiology can evolve under changing infection-pressure conditions. For clinicians and lab directors, results like these support expanding whole-genome or targeted genotyping surveillance to detect emergence and displacement earlier.