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Antibiotic spectrum

Typical activity of 38 antibiotics against 13 organism groups — filter by what must be covered, then open any agent for monitoring, renal dosing, boxed warnings, interactions and pearls.

IDSA AMR 2026 ESBL · CRE · DTR-PA · CRABEUCAST expected resistanceFDA labelingReviewed Oct 2026

1Must cover

Pick one or more. Agents shown must cover every selected group.

2Class, route & search

Typical activity only. Follow your local antibiogram and the isolate's susceptibilities. A dot in the corner means there is a note — tap the agent for it.

✓Reliable±Variable / depends on susceptibility, site or dose–No — expected resistance or not a reliable option

How to read it

What the three levels mean

Reliable (✓) — the agent is expected to be active against usual isolates of that group and is an accepted option (FDA labeling, IDSA guidance). It still assumes a susceptible isolate.

Variable (±) — activity depends on the isolate's susceptibility, the infection site (e.g. cystitis only), the dose, or sources disagree. Every amber cell carries a note.

No (–) — expected (intrinsic) resistance per EUCAST, no activity per FDA labeling, or a guideline advises against relying on the agent even if the lab reports it susceptible (e.g. piperacillin–tazobactam or cefepime for invasive ESBL-E).

The grid describes the organism, not the patient: penetration, source control, allergy, interactions and pregnancy decide the final choice.

Organism groups
    Resistance mechanisms in one table (IDSA 2026)
    PhenotypePreferred (invasive, non-urinary)Avoid
    ESBL-EErtapenem, meropenem, imipenem (meropenem/imipenem if critically ill or hypoalbuminemic)Pip-tazo, cefepime, cephamycins — even if “susceptible”
    AmpC-E (E. cloacae complex, K. aerogenes, C. freundii, H. alvei)Cefepime if MIC ≤8 µg/mL and no ESBL gene; non-β-lactams if susceptible. IDSA does not rank carbapenems first here, and names no specific agent when the cefepime MIC is above 8Ceftriaxone, cefotaxime, ceftazidime and pip-tazo for invasive infection (Q2.4, Q2.5); ceftolozane–tazobactam not suggested for AmpC-E at any site (Q2.6)
    KPC-CREMeropenem–vaborbactam, then ceftazidime–avibactam, then imipenem–relebactam (IDSA lists them alphabetically; the rationale ranks them in this order)Tigecycline/eravacycline for bloodstream or urine
    NDM-CREAztreonam–avibactam or cefiderocol (CZA + aztreonam if aztreonam–avibactam unavailable)CZA alone (no MBL activity)
    OXA-48-CRECeftazidime–avibactamMeropenem–vaborbactam and imipenem–relebactam, even if reported susceptible (Q3.6)
    DTR P. aeruginosaCeftolozane–tazobactam (preferred for pneumonia), ceftazidime–avibactam, imipenem–relebactamRoutine polymyxins; aminoglycoside monotherapy outside urine
    CRABSulbactam–durlobactam + imipenem or meropenemMonotherapy with alternatives

    MDRO: what to treat with (opens in a new tab) turns this table into a culture-directed answer by organism, mechanism and site.

    Agents named here but not in the grid (meropenem–vaborbactam, imipenem–relebactam, sulbactam–durlobactam, aztreonam–avibactam, eravacycline, minocycline, polymyxin B) are reserve or specialist agents. Use them with ID and pharmacy input. Cefepime–enmetazobactam is named by IDSA 2026 for ESBL-E but is listed as Discontinued in Drugs@FDA (NDA 216165, checked 21 Oct 2026), as is plazomicin (NDA 210303); cefepime–taniborbactam is not FDA-approved.

    What was left out, and why

    Pregnancy is flagged only where the FDA label states a specific fetal risk or contraindication. Absent a flag, check a dedicated reference. Doses are not shown. Coverage of organisms outside these 13 groups (Listeria, S. maltophilia, H. influenzae, PJP) appears in agent pearls only where a source states it.

    Sources

    1. Tamma PD, Bonomo RA, Heil EL, Justo JA, Satlin MJ, Mathers AJ. IDSA 2026 Guidance on the Treatment of Antimicrobial Resistant Gram-Negative Infections. Infectious Diseases Society of America; published July 30, 2026 (evidence current to March 1, 2026; replaces the 2024 version).
    2. EUCAST. Expected Resistant Phenotypes, version 1.2, January 2023 (formerly “Intrinsic Resistance and Unusual Phenotypes”).
    3. US FDA prescribing information (DailyMed / openFDA, versions current to Sept 2026): Pfizerpen, ampicillin, amoxicillin–clavulanate, Unasyn, nafcillin, oxacillin, Zosyn, cefazolin, cephalexin, cefuroxime, ceftriaxone, cefepime, Tazicef, Teflaro, Avycaz, Zerbaxa, Fetroja, meropenem, Invanz, Azactam, Emblaveo, vancomycin injection, Vancocin, Dificid, daptomycin, Zyvox, doxycycline hyclate, Tygacil, Zithromax, Cipro, levofloxacin, moxifloxacin, Bactrim / sulfamethoxazole–trimethoprim, Cleocin, Flagyl, Macrobid, fosfomycin tromethamine, gentamicin, tobramycin, amikacin, Coly-Mycin M.
    4. Rybak MJ, Le J, Lodise TP, et al. Therapeutic monitoring of vancomycin for serious MRSA infections: a revised consensus guideline (ASHP/IDSA/PIDS/SIDP). Am J Health Syst Pharm 2020;77:835–64. doi:10.1093/ajhp/zxaa036
    5. Johnson S, Lavergne V, Skinner AM, et al. IDSA/SHEA 2021 focused update guidelines on management of Clostridioides difficile infection in adults. Clin Infect Dis 2021;73:e1029–44. doi:10.1093/cid/ciab549
    6. McDonald LC, Gerding DN, Johnson S, et al. Clinical practice guidelines for C. difficile infection: 2017 update (IDSA/SHEA). Clin Infect Dis 2018;66:e1–48. doi:10.1093/cid/cix1085
    7. Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia (ATS/IDSA). Am J Respir Crit Care Med 2019;200:e45–67. doi:10.1164/rccm.201908-1581ST
    8. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for skin and soft tissue infections: 2014 update by IDSA. Clin Infect Dis 2014;59:e10–52. doi:10.1093/cid/ciu444
    9. 2023 American Geriatrics Society Beers Criteria Update Expert Panel. J Am Geriatr Soc 2023;71:2052–81 (antimicrobial entries: nitrofurantoin, TMP-SMX, ciprofloxacin, macrolides).
    10. Silverman JA, Mortin LI, Vanpraagh AD, Li T, Alder J. Inhibition of daptomycin by pulmonary surfactant. J Infect Dis 2005;191:2149–52. doi:10.1086/430352
    11. Shah PM, Isaacs RD. Ertapenem, the first of a new group of carbapenems. J Antimicrob Chemother 2003;52:538–42.
    12. Köhler T, Kok M, Michea-Hamzehpour M, et al. Multidrug efflux in intrinsic resistance to trimethoprim and sulfamethoxazole in Pseudomonas aeruginosa. Antimicrob Agents Chemother 1996;40:2288–90. doi:10.1128/AAC.40.10.2288
    13. Cooley L, Teng J. Anaerobic resistance: should we be worried? Curr Opin Infect Dis 2019;32:523–30. doi:10.1097/QCO.0000000000000595
    14. US FDA. Rationale for recognition decision: daptomycin (enterococcal breakpoints; CLSI E. faecium SDD breakpoint not recognized).

    Educational reference only — not a substitute for clinical judgment, institutional protocols, or specialist advice. Calculations run in your browser; nothing you enter is sent or stored.