Parallel evolutionary trajectories of extensively drug-resistant Klebsiella pneumoniae ST258 and ST307 pandemic clones: a systematic review

Extensively drug-resistant (XDR) Klebsiella pneumoniae poses a critical threat to global public health. ST258 and ST307 are two pandemic clones that have emerged through distinct evolutionary mechanisms. Understanding their parallel trajectories is essential for clinical management and therapeutic development. This systematic review examined peer-reviewed literature on K. pneumoniae ST258 and ST307 (1995-2025) from PubMed, Scopus, Google Scholar and Web of Science. We extracted data on resistance genes, virulence factors, geographic distribution and clinical outcomes. Inclusion criteria: studies with molecular or genomic characterization of ST258/ST307 isolates. Analysis revealed distinct evolutionary pathways. ST258 (emerged 1995, USA) showed recombinationdriven evolution with stable blaKPC-2/3 resistance, remaining hospital-endemic and declining after 2015. ST307 (emerged 2008, Netherlands) demonstrated plasmid-mediated adaptability with diverse carbapenemases (blaNDM, OXA, KPC), achieving rapid global dissemination across six WHO regions by 2025. Both achieved pandemic status through different mechanisms. ST307 shows emerging hypervirulent sublineages in Europe and South America. Two distinct evolutionary strategies converge to create a unified pandemic threat. ST258's stability contrasts with ST307's adaptability, reflecting different fitness landscapes. Both clones exhibit limited susceptibility to current therapeutic options, with emerging resistance to last-resort agents. ST258 and ST307 represent complementary pandemic threats requiring coordinated global surveillance, antimicrobial development, research into evolutionary dynamics.