Perdigão, JoãoModesto, AnaPereira, A. L.Neto, O.Matos, V.Godinho, A.Phelan, JodyCharleston, JamesSpadar, AntonSessions, Paola Florez deHibberd, MartinCampino, SusanaCosta, A.Fernandes, F.Ferreira, F.Correia, A. B.Gonçalves, LuisaClark, Taane G.Duarte, Aida2025-10-162025-10-162021-06Perdigão et al., Whole-genome sequencing resolves a polyclonal outbreak by extended-spectrum beta-lactam and carbapenem-resistant Klebsiella pneumoniae in a Portuguese tertiary-care hospital. Microbial Genomics, 2020;7(6):000349 DOI 10.1099/mgen.0.0003492057-5858http://hdl.handle.net/10400.26/59236Klebsiella pneumoniae has emerged as an important nosocomial pathogen, with whole-genome sequencing (WGS) significantly improving our ability to characterize associated outbreaks. Our study sought to perform a genome-wide analysis of multiclonal K. pneumoniae isolates (n=39; 23 patients) producing extended spectrum beta-lactamases and/or carbapenemases sourced between 2011 and 2016 in a Portuguese tertiary-care hospital. All isolates showed resistance to third-generation cephalosporins and six isolates (five patients) were also carbapenem resistant. Genome-wide-based phylogenetic analysis revealed a topology representing ongoing dissemination of three main sequence-type (ST) clades (ST15, ST147 and ST307) and transmission across different wards, compatible with missing links that can take the form of undetected colonized patients. Two carbapenemase-coding genes were detected: blaKPC-3, located on a Tn4401d transposon, and blaGES-5 on a novel class 3 integron. Additionally, four genes coding for ESBLs (blaBEL-1, blaCTX-M-8, blaCTX-M-15 and blaCTX-M-32) were also detected. ESBL horizontal dissemination across five clades is highlighted by the similar genetic environments of blaCTX-M-15 gene upstream of ISEcp1 on a Tn3-like transposon. Overall, this study provides a high-resolution genome-wide perspective on the epidemiology of ESBL and carbapenemase-producing K. pneumoniae in a healthcare setting while contributing for the adoption of appropriate intervention and prevention strategies.engESBLKPCCTX-MGram-negativePortugalcontribution to journal10.1099/mgen.0.000349