Comprehensive study reveals heterogeneity among the Klebsiella pneumoniae Species Complex Phenotypes

Here, we conducted a comprehensive analysis of 356 Klebsiella pneumoniae species complex (KpSC) isolates. Overall, K. pneumoniae (82.3%), K. variicola (2.5%) and K. quasipneumoniae (2.5%) were identified. These isolates comprised 321 classical-KpSC, 7 hypervirulent-KpSC and 18 hypermucoviscous-like-KpSC. The cl-KpSC (207/321) and hmv-like-KpSC (8/18) were ESBL-producers and colistin-resistant isolates harboring different types of carbapenemases. Several assays and whole-genome sequencing were performed in a subset of KpSC isolates. Capsule amount differed in all hv and hmv-like produced higher capsule amounts than cl. Murine sepsis model showed that most of cl were nonlethal and unexpectedly some hv required 10 8 CFUs to cause 100% mortality whilst the hmv-like cause 100% mortality with 3x10 8 CFUs. hv-Kpn isolates were associated with ST23-KL1, ST86-KL2, ST380-KL2 and ST3999-KL2; the latter corresponded to a novel hypervirulent clone. Phylogenetic analysis showed that hv-Kpn strains ST23-KL1 and ST86-KL2 were clustered with reference hv-Kpn strains but the hv-Kpn clones ST3999, ST380 and hmv-like-Kpn isolates were closely related to cl-Kpn MDR strains this was supported by a wgSNP-based phylogeny. The information collected here is important to understand how the frequency and evolution of KpSC may changed mainly in Hypervirulent KpSC. Likewise, this study shows the main mechanism of resistance to colistin in Mexico.