Molecular mechanisms responsible KPC-135-mediated resistance to ceftazidime-avibactam in ST11-K47 hypervirulent <i>Klebsiella pneumoniae</i>
Qingyu Shi, Siquan Shen, Chengkang Tang, Li Ding, Yan Guo, Yang Yang, Shi Wu, Renru Han, Dandan Yin, Fupin Hu
Abstract
Ceftazidime-avibactam resistance attributable to the bla KPC-2 gene mutation is increasingly documented in clinical settings.In this study, we characterized the mechanisms leading to the development of ceftazidime-avibactam resistance in ST11-K47 hypervirulent Klebsiella pneumoniae that harboured the bla KPC-135 gene.This strain possessed fimbriae and biofilm, demonstrating pathogenicity.Compared with the wild-type KPC-2 carbapenemase, the novel KPC-135 enzyme exhibited a deletion of Glu168 and Leu169 and a 15-amino acid tandem repeat between Val262 and Ala276.The bla KPC-135 gene was located within the Tn6296 transposon truncated by IS26 and carried on an IncFII/IncR-type plasmid.Compared to the bla KPC-2 -positive cloned strain, only the MIC of ceftazidime increased against bla KPC-135 -positive K. pneumoniae and wasn't inhibited by avibactam (MIC 32 g/mL), while clavulanic acid and vaborbactam demonstrated some inhibition.Kinetic parameters revealed that KPC-135 exhibited a lower K m and kcat/Km with ceftazidime and carbapenems, and a higher (26-fold) 50% inhibitory concentration with avibactam compared to KPC-2.The KPC-135 enzyme exerted a detrimental effect on fitness relative to the wild-type strain.Furthermore, this strain possessed hypervirulent determinants, which included the IncHI1B/FIB plasmid with rmpA2 and expression of type 1 and 3 fimbriae.In conclusion, we reported a novel KPC variant, KPC-135, in a clinical ST11-K47 hypervirulent K. pneumoniae strain, which conferred ceftazidime-avibactam resistance, possibly through increased ceftazidime affinity and decreased avibactam susceptibility.This strain simultaneously harboured resistance and virulence genes, posing an elevated challenge in clinical treatment.