Emergence of Klebsiella variicola positive for NDM-9, a variant of New Delhi metallo-β-lactamase, in an urban river in South Korea

Doris Y.W. Di, Jeonghwan Jang, Tatsuya Unno, Hor Gil Hur

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Objectives: To examine the presence of pathogenic bacteria carrying New Delhi metallo-β-lactamase in the environment and to characterize the genome structures of these strains. Methods: Phenotypic screening of antimicrobial susceptibility and WGS were conducted on three Klebsiella variicola strains possessing NDM-9 isolated froman urban river. Results: Three carbapenem-resistant K. variicola isolated from Gwangju tributary were found to possess blaNDM-9 genes. Antimicrobial susceptibility testing indicated resistance of these strains to aminoglycosides, carbapenems, cephems, folate pathway inhibitors, fosfomycin and penicillins, but susceptibility to fluoroquinolones, phenicols, tetracyclines and miscellaneous agents. WGS revealed that the 108 kb IncFII(Y)-like plasmids carry blaNDM-9 sandwiched between IS15 for the GJ1 strain, IS26 for the GJ2 strain, IS15D1 for the GJ3 strain and ISVsa3, and further bracketed by IS26 and TnAS3 along with the mercury resistance operon upstream and the class 1 integron composed of gene cassettes of aadA2, dfrA12 and sul1 downstream. An aph(30)-Ia gene conferring resistance to aminoglycosides is located after the integrons. Chromosomally encoded blaLEN-13, fosA, aqxA and oqxB genes, as well as plasmid-mediated blaTEM-1B and blaCTX-M-65 encoding ESBL, ant(30)-Ia and mph(A) genes, were also identified. Conclusions: The findings of the present study provide us with the information that NDM-9 has been spreading into the environment. Dissemination of NDM-9 in the environment has raised a health risk alarm as this variant of NDM carries MDR genes with highly transferable mobile genetic elements, increasing the possibility of resistance gene transfer among microorganisms in the environment.

Original languageEnglish (US)
Pages (from-to)1063-1067
Number of pages5
JournalJournal of Antimicrobial Chemotherapy
Issue number4
StatePublished - 2017

Bibliographical note

Publisher Copyright:
© The Author 2016.


Dive into the research topics of 'Emergence of Klebsiella variicola positive for NDM-9, a variant of New Delhi metallo-β-lactamase, in an urban river in South Korea'. Together they form a unique fingerprint.

Cite this