Spread of Plasmid-Encoded NDM-1 and GES-5 Carbapenemases among Extensively Drug-Resistant and Pandrug-Resistant Clinical Enterobacteriaceae in Durban, South Africa

摘要

Whole-genome sequence analyses revealed the presence of blaNDM-1 (n = 31), bla(GES-5) (n = 8), bla(OXA-232) (n = 1), or bla(NDM-5) (n = 1) in extensively drugresistant and pandrug-resistant Enterobacteriaceae organisms isolated from inpatients in 10 private hospitals (2012 to 2013) in Durban, South Africa. Two novel NDM-1-encoding plasmids from Klebsiella pneumoniae were circularized by PacBio sequencing. In p19-10_01 [ IncFIB(K); 223.434 bp], bla(NDM-1) was part of a Tn1548-like structure (16.276 bp) delineated by IS26. The multireplicon plasmid p18-43_01 [ IncR_ 1/IncFIB(pB171)/IncFII(Yp); 212.326 bp] shared an 80-kb region with p19-10_01, not including the bla(NDM-1)-containing region. The two plasmids were used as references for tracing NDM-1-encoding plasmids in the other genome assemblies. The p19-10_01 sequence was detected in K. pneumoniae (n = 7) only, whereas p1843_ 01 was tracked to K. pneumoniae (n = 4), Klebsiella michiganensis (n = 1), Serratia marcescens (n = 11), Enterobacter spp. (n = 7), and Citrobacter freundii (n = 1), revealing horizontal spread of this bla(NDM-1)-bearing plasmid structure. Global phylogeny showed clustering of the K. pneumoniae (18/20) isolates together with closely related carbapenemase-negative ST101 isolates from other geographical origins. The South African isolates were divided into three phylogenetic subbranches, where each group had distinct resistance and replicon profiles, carrying either p19-10_01, p18-10_01, or pCHE-A1 (8,201 bp). The latter plasmid carried bla(GES-5) and aacA4 within an integron mobilization unit. Our findings imply independent plasmid acquisition followed by local dissemination. Additionally, we detected bla(OXA-232) carried by pPKPN4 in K. pneumoniae (ST14) and bla(NDM-5) contained by a pNDM-MGR194-like genetic structure in Escherichia coli (ST167), adding even more complexity to the multilayer molecular mechanisms behind nosocomial spread of carbapenem-resistant Enterobacteriaceae in Durban, South Africa.