Abstract

Colistin is an antibiotic of last resort, but has poor efficacy and resistance is a growing problem. Whilst it is well established that colistin disrupts the bacterial outer membrane by selectively targeting lipopolysaccharide (LPS), it was unclear how this led to bacterial killing. We discovered that MCR-1 mediated colistin resistance in Escherichia coli is due to modified LPS at the cytoplasmic rather than outer membrane. In doing so, we also demonstrated that colistin exerts bactericidal activity by targeting LPS in the cytoplasmic membrane. We then exploited this information to devise a new therapeutic approach. Using the LPS transport inhibitor murepavadin, we were able to cause LPS accumulation in the cytoplasmic membrane of Pseudomonas aeruginosa, which resulted in increased susceptibility to colistin in vitro and improved treatment efficacy in vivo. These findings reveal new insight into the mechanism by which colistin kills bacteria, providing the foundations for novel approaches to enhance therapeutic outcomes.

Data availability

Source data for all figures has been deposited at Dryad: https://doi.org/10.5061/dryad.98sf7m0hh

The following data sets were generated

Article and author information

Author details

  1. Akshay Sabnis

    MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  2. Katheryn L H Hagart

    MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Edinburgh, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  3. Anna Klöckner

    MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  4. Michele Becce

    Department of Materials, Department of Bioengineering, Institute of Biomedical Engineering, Imperial College London, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  5. Lindsay E Evans

    MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  6. R Christopher D Furniss

    Life Sciences, Imperial College London, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-5806-5099
  7. Despoina A I Mavridou

    Department of Molecular Biosciences, University of Texas at Austin, Austin, United States
    Competing interests
    The authors declare that no competing interests exist.
  8. Ronan Murphy

    National Heart and Lung Institute, Imperial College London, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  9. Molly M Stevens

    Department of Materials, Department of Bioengineering, Institute of Biomedical Engineering, Imperial College London, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-7335-266X
  10. Jane C Davies

    National Heart and Lung Institute, Imperial College London, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  11. Gérald J Larrouy-Maumus

    MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  12. Thomas B Clarke

    MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  13. Andrew M Edwards

    MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
    For correspondence
    a.edwards@imperial.ac.uk
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-7173-7355

Funding

Medical Research Council (PhD Studentship)

  • Akshay Sabnis

Wellcome Trust

  • Andrew M Edwards

NIHR Imperial Biomedical Research Centre

  • Andrew M Edwards

DFG

  • Anna Klöckner

Horizon 2020

  • Anna Klöckner

Rosetrees Trust

  • Molly M Stevens

Cystic Fibrosis Trust

  • Jane C Davies

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Animal experimentation: The use of mice was performed under the authority of the UK Home Office outlined in the Animals (Scientific Procedures) Act 1986 after ethical review by Imperial College London Animal Welfare and Ethical Review Body (PPL 70/7969).

Reviewing Editor

  1. Philip A Cole, Harvard Medical School, United States

Publication history

  1. Received: December 16, 2020
  2. Accepted: March 31, 2021
  3. Accepted Manuscript published: April 6, 2021 (version 1)
  4. Version of Record published: May 4, 2021 (version 2)

Copyright

© 2021, Sabnis et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Akshay Sabnis
  2. Katheryn L H Hagart
  3. Anna Klöckner
  4. Michele Becce
  5. Lindsay E Evans
  6. R Christopher D Furniss
  7. Despoina A I Mavridou
  8. Ronan Murphy
  9. Molly M Stevens
  10. Jane C Davies
  11. Gérald J Larrouy-Maumus
  12. Thomas B Clarke
  13. Andrew M Edwards
(2021)
Colistin kills bacteria by targeting lipopolysaccharide in the cytoplasmic membrane
eLife 10:e65836.
https://doi.org/10.7554/eLife.65836

Further reading

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    African trypanosomes proliferate as bloodstream forms (BSFs) and procyclic forms in the mammal and tsetse fly midgut, respectively. This allows them to colonise the host environment upon infection and ensure life cycle progression. Yet, understanding of the mechanisms that regulate and drive the cell replication cycle of these forms is limited. Using single-cell transcriptomics on unsynchronised cell populations, we have obtained high resolution cell cycle regulated (CCR) transcriptomes of both procyclic and slender BSF Trypanosoma brucei without prior cell sorting or synchronisation. Additionally, we describe an efficient freeze–thawing protocol that allows single-cell transcriptomic analysis of cryopreserved T. brucei. Computational reconstruction of the cell cycle using periodic pseudotime inference allowed the dynamic expression patterns of cycling genes to be profiled for both life cycle forms. Comparative analyses identify a core cycling transcriptome highly conserved between forms, as well as several genes where transcript levels dynamics are form specific. Comparing transcript expression patterns with protein abundance revealed that the majority of genes with periodic cycling transcript and protein levels exhibit a relative delay between peak transcript and protein expression. This work reveals novel detail of the CCR transcriptomes of both forms, which are available for further interrogation via an interactive webtool.

    1. Epidemiology and Global Health
    2. Microbiology and Infectious Disease
    Kennedy Lushasi, Kirstyn Brunker ... Katie Hampson
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    Background:

    Dog-mediated rabies is endemic across Africa causing thousands of human deaths annually. A One Health approach to rabies is advocated, comprising emergency post-exposure vaccination of bite victims and mass dog vaccination to break the transmission cycle. However, the impacts and cost-effectiveness of these components are difficult to disentangle.

    Methods:

    We combined contact tracing with whole-genome sequencing to track rabies transmission in the animal reservoir and spillover risk to humans from 2010-2020, investigating how the components of a One Health approach reduced the disease burden and eliminated rabies from Pemba Island, Tanzania. With the resulting high-resolution spatiotemporal and genomic data we inferred transmission chains and estimated case detection. Using a decision tree model we quantified the public health burden and evaluated the impact and cost-effectiveness of interventions over a ten-year time horizon.

    Results:

    We resolved five transmission chains co-circulating on Pemba from 2010 that were all eliminated by May 2014. During this period, rabid dogs, human rabies exposures and deaths all progressively declined following initiation and improved implementation of annual islandwide dog vaccination. We identified two introductions to Pemba in late 2016 that seeded re-emergence after dog vaccination had lapsed. The ensuing outbreak was eliminated in October 2018 through reinstated islandwide dog vaccination. While post-exposure vaccines were projected to be highly cost-effective ($256 per death averted), only dog vaccination interrupts transmission. A combined One Health approach of routine annual dog vaccination together with free post-exposure vaccines for bite victims, rapidly eliminates rabies, is highly cost-effective ($1657 per death averted) and by maintaining rabies freedom prevents over 30 families from suffering traumatic rabid dog bites annually on Pemba island.

    Conclusions:

    A One Health approach underpinned by dog vaccination is an efficient, cost-effective, equitable and feasible approach to rabies elimination, but needs scaling up across connected populations to sustain the benefits of elimination, as seen on Pemba, and for similar progress to be achieved elsewhere.

    Funding:

    Wellcome [207569/Z/17/Z, 095787/Z/11/Z, 103270/Z/13/Z], the UBS Optimus Foundation, the Department of Health and Human Services of the National Institutes of Health [R01AI141712] and the DELTAS Africa Initiative [Afrique One-ASPIRE/DEL-15-008] comprising a donor consortium of the African Academy of Sciences (AAS), Alliance for Accelerating Excellence in Science in Africa (AESA), the New Partnership for Africa's Development Planning and Coordinating (NEPAD) Agency, Wellcome [107753/A/15/Z], Royal Society of Tropical Medicine and Hygiene Small Grant 2017 [GR000892] and the UK government. The rabies elimination demonstration project from 2010-2015 was supported by the Bill & Melinda Gates Foundation [OPP49679]. Whole-genome sequencing was partially supported from APHA by funding from the UK Department for Environment, Food and Rural Affairs (Defra), Scottish government and Welsh government under projects SEV3500 & SE0421.