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J Antimicrob Chemother. 2018 Apr 10. doi: 10.1093/jac/dky121. [Epub ahead of print]

Antibiotic pressure on the acquisition and loss of antibiotic resistance genes in Klebsiella pneumoniae.

Author information

Division of Medical Microbiology, Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA.
Simons Center for Quantitative Biology, Cold Spring Harbor, NY, USA.
Division of Pediatric Infectious Diseases, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Department of Computer Science, Johns Hopkins University, Baltimore, MD, USA.
Department of Biology, Johns Hopkins University, Baltimore, MD, USA.



In this study, we characterize a concurrent disseminated infection with a virulent hypermucoviscous (HMV) Klebsiella pneumoniae and an OXA-181-producing XDR K. pneumoniae from a patient with recent hospitalization in India. During exposure to meropenem therapy, the highly susceptible HMV K. pneumoniae became resistant to carbapenems, consistent with the acquisition of blaOXA-181.


Twelve K. pneumoniae isolates were recovered from the patient and the hospital room environment over a 3 month hospitalization. Phenotypic and molecular studies were completed to characterize the isolates. Oxford Nanopore and Illumina MiSeq WGS were performed to study phylogeny (MLST and SNPs), plasmids and virulence genes and demonstrate changes in the organism's resistome that occurred over time.


WGS revealed that the HMV K. pneumoniae belonged to ST23 and harboured an IncH1B virulence plasmid, while the XDR K. pneumoniae belonged to ST147 and possessed two MDR plasmids (IncR and IncFII), the blaOXA-181-bearing ColKP3 plasmid and chromosomal mutations conferring the XDR phenotype. Sequential isolates demonstrated plasmid diversification (fusion of the IncR and IncFII plasmids), mobilization of resistance elements (ompK35 inactivation by ISEcp1-blaCTX-M-15 mobilization, varying numbers of resistance genes on plasmid scaffolds) and chromosomal mutations (mutations in mgrB) leading to further antibiotic resistance that coincided with antibiotic pressure. Importantly, the HMV strain in this study was unable to preserve the carbapenem-resistant phenotype without the selective pressure of meropenem.


To the best of our knowledge, we are the first to report a carbapenem-resistant HMV K. pneumoniae strain in the USA. Ultimately, this case demonstrates the role of antibiotic pressure in the acquisition and loss of important genetic elements.

[Available on 2019-07-01]

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