The increasing prevalence of multidrug-resistant Klebsiella pneumoniae has led to a resurgence in the use of colistin as a last-resort drug. Colistin is a cationic antibiotic that selectively acts on Gram-negative bacteria through electrostatic interactions with anionic phosphate groups of the lipid A moiety of lipopolysaccharides (LPSs). Colistin resistance in K. pneumoniae is mediated through loss of these phosphate groups, their modification by cationic groups, and by the hydroxylation of acyl groups of lipid A. Here, we study the in vitro evolutionary trajectories toward colistin resistance in four clinical K. pneumoniae complex strains and their impact on fitness and virulence characteristics. Through population sequencing during in vitro evolution, we found that colistin resistance develops through a combination of single nucleotide polymorphisms, insertions and deletions, and the integration of insertion sequence elements, affecting genes associated with LPS biosynthesis and modification and capsule structures. Colistin resistance decreased the maximum growth rate of one K. pneumoniae sensu stricto strain, but not those of the other three K. pneumoniae complex strains. Colistin-resistant strains had lipid A modified through hydroxylation, palmitoylation, and L-Ara4N addition. K. pneumoniae sensu stricto strains exhibited cross-resistance to LL-37, in contrast to the Klebsiella variicola subsp. variicola strain. Virulence, as determined in a Caenorhabditis elegans survival assay, was increased in two colistin-resistant strains. Our study suggests that nosocomial K. pneumoniae complex strains can rapidly develop colistin resistance through diverse evolutionary trajectories upon exposure to colistin. This effectively shortens the life span of this last-resort antibiotic for the treatment of infections with multidrug-resistant Klebsiella.
Bibliographical noteFunding Information:
W.v.S. was funded by the Netherlands Organisation for Scientific Research through a Vidi grant (grant no. 917.13.357) and a Royal Society Wolfson Research Merit Award (grant no. WM160092). Work in the laboratory of J.A.B. was supported by the Biotechnology and Biological Sciences Research Council BBSRC, (grant no. BB/N00700X/1, BB/P020194/1, and BB/P006078/1) and a Queen’s University Belfast start-up grant. S.H.M.R. was funded by an ERC Starting grant (grant no. 639209-ComBact). The funders had no role in study design, data collection and interpretation, the decision to submit the work for publication, or manuscript preparation. The authors have declared that no competing interests exist.
© 2020 American Society for Microbiology. All Rights Reserved.
Copyright 2020 Elsevier B.V., All rights reserved.
- Antibiotic resistance
ASJC Scopus subject areas
- Pharmacology (medical)
- Infectious Diseases