Letter | Published:

Staphylococcus aureus inactivates daptomycin by releasing membrane phospholipids

Nature Microbiology volume 2, Article number: 16194 (2016) | Download Citation

Abstract

Daptomycin is a bactericidal antibiotic of last resort for serious infections caused by methicillin-resistant Staphylococcus aureus (MRSA)1,2. Although resistance is rare, treatment failure can occur in more than 20% of cases3,4 and so there is a pressing need to identify and mitigate factors that contribute to poor therapeutic outcomes. Here, we show that loss of the Agr quorum-sensing system, which frequently occurs in clinical isolates, enhances S. aureus survival during daptomycin treatment. Wild-type S. aureus was killed rapidly by daptomycin, but Agr-defective mutants survived antibiotic exposure by releasing membrane phospholipids, which bound and inactivated the antibiotic. Although wild-type bacteria also released phospholipid in response to daptomycin, Agr-triggered secretion of small cytolytic toxins, known as phenol soluble modulins, prevented antibiotic inactivation. Phospholipid shedding by S. aureus occurred via an active process and was inhibited by the β-lactam antibiotic oxacillin, which slowed inactivation of daptomycin and enhanced bacterial killing. In conclusion, S. aureus possesses a transient defence mechanism that protects against daptomycin, which can be compromised by Agr-triggered toxin production or an existing therapeutic antibiotic.

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Acknowledgements

The authors thank the following for providing bacterial strains, phage or reagents: J.M. Van Dijl (University Medical Center Groningen), M. Otto (NIH, Bethesda), R. Massey (University of Bath), M. Horsburgh (University of Liverpool), T. Foster (Trinity College Dublin) and the Network on Antimicrobial Resistance in Staphylococcus aureus (NARSA) Program under NIAID/NIH contract no. HHSN272200700055C. L. Haigh (Imperial College) is thanked for analysing modified daptomycin samples. A. Nobbs (University of Bristol) is acknowledged for helpful discussions and comments on the manuscript. A.M.E. acknowledges funding from the Department of Medicine, Imperial College. S.W. acknowledges funding from the BBSRC and Wellcome Trust. K.L.P. is supported by a PhD studentship from the Faculty of Medicine, Imperial College London. S.H. is supported by a scholarship from the Inlaks Shivdasani Foundation. T.B.C. is a Sir Henry Dale Fellow jointly funded by the Wellcome Trust and Royal Society (grant no. 107660/Z/15/Z).

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Affiliations

  1. MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, London SW7 2AZ, UK

    • Vera Pader
    • , Sanika Hakim
    • , Kimberley L. Painter
    • , Sivaramesh Wigneshweraraj
    • , Thomas B. Clarke
    •  & Andrew M. Edwards

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Contributions

V.P., S.W., T.B.C. and A.M.E. designed the experiments. V.P., S.H., T.B.C. and A.M.E. performed experiments. K.L.P. generated and characterized mutants. V.P., S.H., T.B.C. and A.M.E. analysed data. All authors contributed to the writing of the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Andrew M. Edwards.

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https://doi.org/10.1038/nmicrobiol.2016.194

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