Communicable E59: 'Ask me anything' – EUCAST and CLSI leadership explain

In this episode of *Communicable*, Nav Narayanan and Thomas Tängdén kick off the first 'Ask me anything' episode, inviting EUCAST and CLSI leadership Sören Gatermann, Christian Giske and Amy Mathers to answer questions from our listeners. Together, they discuss the roles and operations of both organisations, similarities and differences between EUCAST and CLSI, how breakpoints and guidance documents are developed, set the record straight about the 'I' category, explain which data inform breakpoint decisions, and much more. This episode was edited by *Communicable*'s executive producer, Angela Huttner.   **Further reading** Documents/resources: - CLSI MicroFree, https://em100.edaptivedocs.net/Login.aspx?ru=1 - EUCAST: When there are no antifungal breakpoints - EUCAST: When there are no breakpoints? - Use\of\fosfomycin\iv\breakpoints\General\advice\_20240528.pdf - EUCAST: Definition of S, I and R - EUCAST Guidance Document, “When there are no breakpoints”, https://www.eucast.org/bacteria/guidance-documents/ - EUCAST Guidance Document for “Rare Yeasts”, https://www.eucast.org/fungi-afst/guidance-documents/ Articles (alphabetical):  - Bixby ML, et al. Fosfomycin Disk Diffusion Testing among *Klebsiella pneumoniae* Results in Frequent Inner Colonies and Categorical Disagreement Based on Conflicting Breakpoint Organization Recommendations. *Microbiol Spectr* 2023. DOI: 10.1128/spectrum.03363-22 - DeMarco MG, et al. Impact of media brand on cefiderocol disk diffusion results. *J Clin Microbiol* 2025. DOI: 10.1128/jcm.01648-24 - Giske CG, et al. Aminoglycoside breakpoints-the EUCAST approach and what this means for the clinician. *CMI* 2025. DOI: 10.1016/j.cmi.2025.08.015 - Mouton JW, et al. MIC-based dose adjustment: facts and fables. *J Antimicrob Chemother* 2018. DOI: 10.1093/jac/dkx427 - Narayanan N, et al. Amoxicillin-Clavulanate Breakpoints Against *Enterobacterales*: Rationale for Revision by the CLSI. *Clin Infect Dis* 2024. DOI: 10.1093/cid/ciae201 - Narayanan N, et al. Amoxicillin-Clavulanate Breakpoints Against *Enterobacterales*: Rationale for Revision by the Clinical and Laboratory Standards Institute. *Clin Infect Dis* 2024. DOI: - Pham Thanh D, et al. A novel ciprofloxacin-resistant subclade of H58 Salmonella Typhi is associated with fluoroquinolone treatment failure. *eLife* 2016. DOI: 10.7554/eLife.14003.001 - Smekal A. Swedish multicentre study of target attainments with β-lactams in the ICU: which MIC parameter should be used? *J Antimicrob Chemother* 2023. DOI: 10.1093/jac/dkad327 - Turnidge J, et al. How to: the application and analysis of categorical agreement in antimicrobial susceptibility testing using EUCAST breakpoints. *CMI* 2026. DOI: 10.1016/j.cmi.2025.12.018 - Turnidge J, et al. Rationale for contemporary antimicrobial treatment of *Stenotrophomonas maltophilia*: a narrative review. *CMI Comms* 2025. DOI: 10.1016/j.cmicom.2025.105082 - Weinstein M, et al. The CLSI Subcommittee on Antimicrobial Susceptibility Testing: Background, Organization, Functions, and Processes. *J Clin Microbiol* 2020. DOI: 10.1128/jcm.01864-19