show Abstracthide AbstractThe Specialist Antimicrobial Chemotherapy Unit (SACU) based at Public Health Wales (PHW) Microbiology in Cardiff provides a reference laboratory service for the identification and confirmation of antimicrobial resistance mechanisms in bacterial isolates including Klebsiella, referred by microbiology laboratories across and beyond Wales. It also collects Klebsiella (and other bacterial) isolates from blood cultures for surveillance purposes and receives isolates from suspected outbreaks as part of the development of PHW's Whole Genome Sequencing (WGS) based typing program. This study describes the retrospective genomic analysis of a collection of Klebsiella isolates (n=540) gathered by SACU between 2007 and 2020. Using a combination of short- and long-read sequencing, our analysis revealed detailed insights into the evolutionary dynamics of the major K. pneumoniae clones and plasmids driving spread of antibiotic resistance genes in Wales. Our data provide important considerations for the design and optimisation of routine genomic surveillance systems in public health laboratories.