Edited by Simon A. Levin, Princeton University, Princeton, NJ, and approved May 11, 2015 (received for review January 16, 2015)
Klebsiella pneumoniae is rapidly becoming untreatable using last-line antibiotics. It is especially problematic in hospitals, where it causes a range of acute infections. To approach controlling such a bacterium, we first must define what it is and how it varies genetically. Here we have determined the DNA sequence of K. pneumoniae isolates from around the world and present a detailed analysis of these data. We show that there is a wide spectrum of diversity, including variation within shared sequences and gain and loss of whole genes. Using this detailed blueprint, we show that there is an unrecognized association between the possession of specific gene profiles associated with virulence and antibiotic resistance and the differing disease outcomes seen for K. pneumoniae.
Klebsiella pneumoniae is now recognized as an urgent threat to human health because of the emergence of multidrug-resistant strains associated with hospital outbreaks and hypervirulent strains associated with severe community-acquired infections. K. pneumoniae is ubiquitous in the environment and can colonize and infect both plants and animals. However, little is known about the population structure of K. pneumoniae, so it is difficult to recognize or understand the emergence of clinically important clones within this highly genetically diverse species. Here we present a detailed genomic framework for K. pneumoniae based on whole-genome sequencing of more than 300 human and animal isolates spanning four continents. Our data provide genome-wide support for the splitting of K. pneumoniae into three distinct species, KpI (K. pneumoniae), KpII (K. quasipneumoniae), and KpIII (K. variicola). Further, for K. pneumoniae (KpI), the entity most frequently associated with human infection, we show the existence of >150 deeply branching lineages including numerous multidrug-resistant or hypervirulent clones. We show K. pneumoniae has a large accessory genome approaching 30,000 protein-coding genes, including a number of virulence functions that are significantly associated with invasive community-acquired disease in humans. In our dataset, antimicrobial resistance genes were common among human carriage isolates and hospital-acquired infections, which generally lacked the genes associated with invasive disease. The convergence of virulence and resistance genes potentially could lead to the emergence of untreatable invasive K. pneumoniae infections; our data provide the whole-genome framework against which to track the emergence of such threats.
Author contributions: K.E.H., H.W., R.A.S., and N.R.T. designed research; K.E.H. performed research; H.W., R.N.Z., S. Baker, C.A.W., D.D., A.J., L.Y.H., J.S., S. Brisse, H.C., J.W., K.V.N., T.V.N., T.T.D., M.M., V.L.M., N.T.K.N., C.S., K.K., P.N.N., and C.E.M. contributed new reagents/analytic tools; K.E.H., T.R.C., C.G., M.B.S., D.J.E., and N.R.T. analyzed data; and K.E.H. and N.R.T. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The sequences reported in this paper have been deposited in the European Nucleotide Archive database (accession no. ERP000165).
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1501049112/-/DCSupplemental.
Freely available online through the PNAS open access option.
