Clonal transmission of polymyxin B-resistant hypervirulent Klebsiella pneumoniae isolates coharboring blaNDM-1 and blaKPC-2 in a tertiary hospital in China
Mengli Tang, Jun Li, Zhaojun Liu, Fengjun Xia, Changhang Min, Yongmei Hu, Haichen Wang, Mingxiang Zou
Abstract
Abstract Background The prevalence of multidrug-resistant hypervirulent K. pneumoniae (MDR-hvKP) has gradually increased. It poses a severe threat to human health. However, polymyxin-resistant hvKP is rare. Here, we collected eight polymyxin B-resistant K. pneumoniae isolates from a Chinese teaching hospital as a suspected outbreak. Results The minimum inhibitory concentrations (MICs) were determined by the broth microdilution method. HvKP was identified by detecting virulence-related genes and using a Galleria mellonella infection model. Their resistance to serum, growth, biofilm formation, and plasmid conjugation were analyzed in this study. Molecular characteristics were analyzed using whole-genome sequencing (WGS) and mutations of chromosome-mediated two-component systems pmrAB and phoPQ , and the negative phoPQ regulator mgrB to cause polymyxin B (PB) resistance were screened. All isolates were resistant to polymyxin B and sensitive to tigecycline; four were resistant to ceftazidime/avibactam. Except for KP16 (a newly discovered ST5254), all were of the K64 capsular serotype and belonged to ST11. Four strains co-harbored bla KPC-2 , bla NDM-1 , and the virulence-related genes p rmpA , p rmpA2 , iucA , and peg344 , and were confirmed to be hypervirulent by the G. mellonella infection model. According to WGS analysis, three hvKP strains showed evidence of clonal transmission (8–20 single nucleotide polymorphisms) and had a highly transferable pKOX_NDM1-like plasmid. KP25 had multiple plasmids carrying bla KPC-2 , bla NDM-1 , bla SHV-12 , bla LAP-2 , tet(A) , fosA5, and a pLVPK-like virulence plasmid. Tn 1722 and multiple additional insert sequence-mediated transpositions were observed. Mutations in chromosomal genes phoQ and pmrB , and insertion mutations in mgrB were major causes of PB resistance. Conclusions Polymyxin-resistant hvKP has become an essential new superbug prevalent in China, posing a serious challenge to public health. Its epidemic transmission characteristics and mechanisms of resistance and virulence deserve attention.