Phylogenomics of globally spread Clonal Groups 14 and 15 of Klebsiella pneumoniae

The increasing worldwide spread of multidrug-resistant (MDR) Kp is largely driven by high-risk sublineages, some of them well-characterised such as Clonal Group (CG) 258, CG147 or CG307. MDR Kp Sequence-Type (ST) 14 and ST15 have been described worldwide causing frequent outbreaks of CTX-M-15 and/or carbapenemase producers. However, their phylogeny, population structure and global dynamics remain unclear. Here, we clarify the phylogenetic structure and evolvability of CG14 and CG15 Kp by analysing the CG14 and CG15 genomes available in public databases (n=481, November 2019) and de novo sequences representing main sublineages circulating in Portugal (n=9). Deduplicated genomes (n=235) were used to infer temporal phylogenetic evolution and to compare their capsular locus (KL), resistome, virulome and plasmidome using high-resolution tools. Phylogenetic analysis supported independent evolution of CG14 and CG15 within two distinct clades and 4 main subclades which are mainly defined according to the KL and the accessory genome. Within CG14, two large monophyletic subclades, KL16 (14%) and KL2 (86%), presumptively emerged around 1937 and 1942, respectively. Sixty-five percent of CG14 carried genes encoding ESBL, AmpC and/or carbapenemases and, remarkably, they were mainly observed in the KL2 subclade. The CG15 clade was segregated in two major subclades. One was represented by KL24 (42%) and KL112 (36%), the latter one diverging from KL24 around 1981, and the other comprised KL19 and other KL-types (16%). Of note, most CG15 genomes contained genes encoding ESBL, AmpC and/or carbapenemases (n=148, 87%) and displayed a characteristic set of mutations in regions encoding quinolone resistance (QRDR, GyrA83F/GyrA87A/ParC80I). Plasmidome analysis revealed 2463 plasmids grouped in 27 predominant plasmid groups (PG) with a high degree of recombination, including particularly pervasive F-type (n=10) and Col (n=10) plasmids. Whereas blaCTX-M-15 was linked to a high diversity of mosaic plasmids, other ARGs were confined to particular plasmids (e.g. blaOXA-48-IncL; blaCMY/TEM-24-IncC). This study firstly demonstrates an independent evolutionary trajectory for CG15 and CG14, and suggests how the acquisition of specific KL, QRDR mutations (CG15) and ARGs in highly recombinant plasmids could have shaped the expansion and diversification of particular subclades (CG14-KL2, CG15-KL24/KL112). IMPORTANCEKlebsiella pneumoniae (Kp) represents a major threat in the burden of antimicrobial resistance (AMR). Phylogenetic approaches to explain the phylogeny, emergence and evolution of certain multidrug resistant populations have mainly focused on core-genome approaches while variation in the accessory genome and the plasmidome have been long overlooked. In this study, we provide unique insights into the phylogenetic evolution and plasmidome of two intriguing and yet uncharacterized clonal groups (CGs), the CG14 and CG15, which have contributed to the global dissemination of contemporaneous {beta}-lactamases. Our results point-out an independent evolution of these two CGs and highlight the existence of different clades structured by the capsular-type and the accessory genome. Moreover, the contribution of a turbulent flux of plasmids (especially multireplicon F type and Col) and adaptive traits (antibiotic resistance and metal tolerance genes) to the pangenome, reflect the exposure and adaptation of Kp under different selective pressures.