Clinical breakpoints and dosing of antibiotics

About Clinical breakpoint tables.

Clinical breakpoints are for everyday use in the clinical laboratory to advise on patient therapy. Breakpoint tables are updated on the 1st of January each year. Tentative new tables are published in December - this is for consultation and to permit laboratories to prepare for changes introduced in the next version. Between the yearly updates, errata may be published as a new version of the breakpoint table whereby the version number is increased from X.0 to X.1. Should there be a need to change or add to breakpoints between new versions of the tables, these are are published as amendments in a separate document. 

In EUCAST tables, the I category is not listed. It is implied as the values between the S breakpoint and the R breakpoint.

For a breakpoint listed as S<=1 mg/L and R>8 mg/L the intermediate category is 2 - 8 (technically >1 - 8) mg/L.

For a breakpoint listed as S>=22 mm and R<18 mm the intermediate category is 18-21 mm. For species where no "susceptible" category (S) exists and for which isolates without resistance mechanisms are categorised as "intermediate" (I), an arbitrary breakpoint of S≤0.001 mg/L is used to signal that no isolates are expected to be categorised "S". For disk diffusion susceptibility testing the corresponding arbitrary breakpoint is S≥50 mm.