Potential conflicts of interest. G. S. reports speaking honoraria from AbbVie, Paratek, and Sunovion; consulting fees from Octapharma, Inc, Ferring, AbbVie, and Paratek; research funding from Octapharma, Inc; grants or contracts from Octapharma, Inc (paid to Sharp Healthcare); a National Institutes of Health (NIH) research grant (paid to University of California–San Diego School of Medicine); royalties paid to author from Up-to-Date; participation on an NIH data and safety monitoring board or advisory board (University of California–San Diego School of Medicine); receipt of equipment, materials, drugs, medical writing, gifts, or other services from Octapharma, Inc (made to Sharp Healthcare); and other financial or nonfinancial interests with the Massachusetts Medical Society (New England Journal of Medicine–Infectious Disease Journal Watch, editor/author fees). S. A. is an employee of Seres Therapeutics (after the submission of the original manuscript). M. J. R. reports grant support, consulting, or speaking on behalf of AbbVie (consulting fees and payment or honoraria for speaking), Melinta, Merck (consulting fees), Paratek, Shionogi (consulting fees and payment or honoraria for speaking), T2 Biosystems (consulting fees), and Tetraphase and is partially supported by NIH R21 Al163726. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.