Background: Ceftriaxone-resistant (CRO-R) Escherichia coli bloodstream infections (BSIs) are common., Methods: This is a prospective cohort of patients with E coli BSI at 14 United States hospitals between November 2020 and April 2021. For each patient with a CRO-R E coli BSI enrolled, the next consecutive patient with a ceftriaxone-susceptible (CRO-S) E coli BSI was included. Primary outcome was desirability of outcome ranking (DOOR) at day 30, with 50% probability of worse outcomes in the CRO-R group as the null hypothesis. Inverse probability weighting (IPW) was used to reduce confounding., Results: Notable differences between patients infected with CRO-R and CRO-S E coli BSI included the proportion with Pitt bacteremia score ≥4 (23% vs 15%, P = .079) and the median time to active antibiotic therapy (12 hours [interquartile range {IQR}, 1-35 hours] vs 1 hour [IQR, 0-6 hours]; P < .001). Unadjusted DOOR analyses indicated a 58% probability (95% confidence interval [CI], 52%-63%) for a worse clinical outcome in CRO-R versus CRO-S BSI. In the IPW-adjusted cohort, no difference was observed (54% [95% CI, 47%-61%]). Secondary outcomes included unadjusted and adjusted differences in the proportion of 30-day mortality between CRO-R and CRO-S BSIs (-5.3% [95% CI, -10.3% to -.4%] and -1.8 [95% CI, -6.7% to 3.2%], respectively), postculture median length of stay (8 days [IQR, 5-13 days] vs 6 days [IQR, 4-9 days]; P < .001), and incident admission to a long-term care facility (22% vs 12%, P = .045)., Conclusions: Patients with CRO-R E coli BSI generally have poorer outcomes compared to patients infected with CRO-S E coli BSI, even after adjusting for important confounders., Competing Interests: Potential conflicts of interest. J. G.-D. reports grants and contracts paid to her institution from the NIH, the Biomedical Advanced Research and Development Authority, Janssen Research & Development, Pfizer, BioNTech SE, GCAR, Hoffman La-Roche, I-Mab Biopharma, Rebiotix, Target Health, OBO Lilly USA, GlaxoSmithKline (GSK), Summit Ltd, UK, Cidara Therapeutics, Merck Sharp & Dohme (MSD), Seres Therapeutics, and Theratechnologies; and Infectious Diseases Society of America (IDSA) Research Committee participation paid to her directly. Y. D. reports grants and contracts paid to his institution from Entasis, Asahi Kasei Pharma, and Shionogi; consulting fees paid directly to him by Meiji Seika Pharma, Shionogi, Gilead, MSD, Chugai, bioMérieux, and GSK; and speaker payments from MSD, Shionogi, AstraZeneca, Teijin Healthcare, Gilead, FujiFilm Toyama Chemical, bioMérieux, H.U. Frontier, and Eiken Chemical. C. A. A. reports grants and contracts paid to his institution from NIH/NIAID (1 P01 AI152999, R01 AI148342, R01 AI134637, T32 AI141349, K24 AI121296, U19 AI144297, R01 AI150685, R21 AI151536), MeMed Diagnostics, Entasis Therapeutics, Merck Pharmaceuticals, and Harris County Public Health; payments to him for UpToDate royalties; reimbursement of meeting attendance and speaking from IDSA, American Society for Microbiology, Society of Hospital Epidemiology of America, European Society for Clinical Microbiology and Infectious Diseases, bioMérieux Foundation, Sociedad Argentina de Infectologia, Sociedad Chilena de Infectologia, Sociedad Colombiana de Infectologia, Panamerican Society for Infectious Diseases, and Brazilian Society for Infectious Diseases; reviewer participation as part of the NIH grant Review Study Sections; travel expenses from the IDSA Board of Directors; and for Editor in Chief for Antimicrobial Agents and Chemotherapy; nonpaid participation includes the World Health Organization Antibacterial Pipeline Advisory Group and participation on the IDSA Board of Directors. E. S. reports grants and contracts paid to his institution from Janssen Pharmaceuticals; speaker fees paid directly to him from Janssen Pharmaceuticals; and participation on a steering committee with no payment involved from Janssen Pharamceuticals. L. G. M. reports grants and contracts paid to his institution from Merck, Medline, Contrafect, and GSK. M. J. S. reports grants and contracts paid to his institution from Merck, Allergan, BioFire Diagnostics, Affinity Biosensors, and SNIPRBiome; consulting fees paid directly to him by Shionogi; and participation on a data and safety monitoring board paid directly to him by Spero Therapeutics. M. K. reports participating on an advisory board with payments made directly to him from Melinta, and receipt of drugs or other services paid directly to his institution by NIH. W. C. H. participates as a member of an endpoint adjudication committee for Pfizer; is a member of the advisory board for ADMA Biologics; and has stock ownership in Pfizer, Bristol-Myers Squibb, and Zimmer Biomet. R. P. reports grants from BioFire, ContraFect, and TenNor Therapeutics; is a consultant to Curetis, Abbott Laboratories, Next Gen Diagnostics, PathoQuest, Selux Diagnostics, 1928 Diagnostics, PhAST, Day Zero Diagnostics, Torus Biosystems, Mammoth Biosciences, and Qvella; is a consultant to Netflix and CARB-X; has a patent on Bordetella pertussis (parapertussis) polymerase chain reaction issued, a patent on a device and method for sonication (with royalties paid by Samsung), and a patent on an anti-biofilm substance issued; receives an editor's stipend from the IDSA; and receives honoraria from the National Board of Medical Examiners, UpToDate, and the Infectious Diseases Board Review Course. Other interests paid to her institution include Adaptive Phase Therapeutics and Pathogenomix. S. R. E. reports grants from the NIAID/NIH and De Gruyter (Editor in Chief for Statistical Communications in Infectious Diseases); royalties from Taylor & Francis; consulting fees from Genentech, AstraZeneca, Takeda, Microbiotix, Johnson & Johnson, Endologix, ChemoCentryx, Becton Dickinson, Atricure, Roviant, Neovasc, Nobel Pharma, Horizon, International Drug Development Institute, and SVB Leerink; payments from Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION); meeting support from the US Food and Drug Administration, the Deming Conference on Applied Statistics, the Clinical Trial Transformation Initiative, the Council for International Organizations of Medical Sciences, the International Chinese Statistical Association Applied Statistics Symposium, and the Antimicrobial Resistance and Stewardship Conference; and board member participation for the NIH, the Breast International Group, the University of Pennsylvania, Duke University, Roche, Pfizer, Takeda, Akouos, Apellis, Teva, Vir, DayOneBio, Alexion, Tracon, Rakuten, AbbVie, GSK, Eli Lilly, Nuvelution, Clover, FHI Clinical, Lung Biotech, SAB Biopharm, Advantagene, Candel, the American Statistical Association, the Society for Clinical Trials, and the Frontier Science Foundation. H. F. C. reports participation on a Merck data and safety monitoring board for molnupiravir paid directly to him, and stock ownership in Moderna and Merck. V. G. F. reports grants to his institution from the NIH, MedImmune, Allergan, Pfizer, Advanced Liquid Logics, Theravance, Novartis, Merck, Medical Biosurfaces, Locus, Affinergy, Contrafect, Karius, Genentech, Regeneron, Basilea, and Janssen; royalties from UpToDate; personal fees from Novartis, Debiopharm, Genentech, Achaogen, Affinium, The Medicines Co, MedImmune, Bayer, Basilea, Affinergy, Janssen, Contrafect, Regeneron, Destiny, Amphliphi Biosciences, Integrated Biotherapeutics, C3J, Armata, Valanbio, Akagera, Aridis, and Roche; editorial stipend from IDSA; pending patent for a host gene expression signature diagnostic for sepsis; leadership role as associate editor for Clinical Infectious Diseases; and stock options with Valanbio and ArcBio. D. v. D. reports grants and contracts from the NIH and Merck, paid to his institution, outside the published work, and grants from Shionogi paid to him; consultancy for Actavis, Tetraphase, Sanofi Pasteur, Medimmune, Astellas, Merck, Allergan, T2 Biosystems, Roche, Achaogen, Neumedicine, Shionogi, Pfizer, Entasis, QPex, Wellspring, Karius, Utility, and Union; payment for honoraria from Pfizer; and an editor's stipend from the British Society for Antimicrobial Chemotherapy. All other authors report no potential conflicts., (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)