Clinical breakpoints and dosing of antibiotics

06 January 2021

Clinical breakpoints - breakpoints and guidance


Before using the EUCAST breakpoint tables - make sure you read this.

There are changes in the breakpoint tables every year. Some may be difficult to understand or accept without having followed the development of and consultations on the changing definitions of the susceptibility categories, especially the change from the old "intermediate" (I) to the new "Susceptible, increased exposure" (I). To emphasise the need for high exposure already for wild type isolates, there are now some species/agents which are never categorised "Susceptible, standard dose" (S), only "Susceptible, increased exposure" (I). To make sure these are never reported S, an arbitrary breakpoint of S ≤0.001 mg/L (corresponding to disk diffusion S≥50 mm) is introduced. These are meant to be off-scale and not part of testing. For these, do not aim to include concentrations of the agent that will distinguish between S and I - include only concentrations to reliably distinguish between I and R.

Users of the tables are urged to inform themselves on definitions of S, I and R, the use of the arbitrary, off-scale breakpoints and the fact that Pseudomonas aeruginosa, for many agents, is never reported S, only I, but is still possible to treat provided the dosing and mode of administration is considered.

Visit the section on new definitions of S, I and R, the recorded webinar on how to handle the "Susceptible, increased exposure category" and read the first few tabs in the breakpoint table (Notes, Guidance, Dosage, Technical uncertainty).

For questions and comments on breakpoints, use the EUCAST subject related contact form.



The 2021, v 11.0 breakpoint table for bacteria has new agents, new species, revised breakpoints, a revised dosage table, and specific breakpoints for the treatment of meningitis. Agents where specific breakpoints were not assigned for meningitis should normally be avoided in the treatment of meningitis (exceptions Listeria monocytogenes and ampicillin and Neisseria meningitidis and benzylpenicillin, cefotaxime and ceftriaxone). For some uncommon meningitis bacteria, alternatives may be scarce. Make sure the agent is at all relevant, that maximum exposure is achieved and only consider treating wild type organisms, i.e. isolates lacking resistance mechanisms to the agent.

Make sure the device you are using for the presentation of tables can correctly display footnotes (Note1,Note2) and other typographical tools. 


Clarification concerning Staphylococci (2021-02-09): For coagulase-positive species other than S. aureus (S argenteus, S. schweizeri, S. intermedius, S. pseudintermedius and S. coagulans) there is limited information on the performance of breakpoints for most agents. Where such information exists, specific breakpoints are provided. For S. argenteus, breakpoints for S. aureus can be used without caveats. For S. coagulans, the oxacillin disk and criteria listed for S. pseudintermedius and S. schleiferi should be used.
Erratum in the Staphylococcus spp tab (fluroquinolone section): Footnote C should read:  Isolates categorised as susceptible to norfloxacin can be reported susceptible (S) to moxifloxacin and "susceptible increased exposure" (I) to ciprofloxacin and levofloxacin. Isolates non-wild type to norfloxacin should be tested for susceptibility to individual agents.


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Breakpoints published in Addendum during the year will be part of the next version of the full Clinical breakpoint tables valid from early January each year.


Previous versions of breakpoint tables:

Previous versions of breakpoint tables. 

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Definitions of clinical breakpoints and epidemiological cut off values

Modified definitions valid from 1 January, 2019.







Breakpoint tables

Make sure the device you are using for the presentation of tables can correctly display footnotes (Note1,Note2) and other typographical tools.