European Committee on Antimicrobial Susceptibility Testing - eucast

Haemophilus influenzae
Monobactams MIC breakpoint Disk Zone diameter Notes
(mg/L) content breakpoint (mm) Numbers for comments on MIC breakpoints
(µg)
Letters for comments on disk diffusion
S ≤ R > S ≥ R <
Aztreonam IE IE IE IE
Levofloxacin 1 2 1 5 26 26
Moxifloxacin 0.5 2 0.5 5 25 25
Nalidixic acid (screen) NA NA 30 23 A
Norfloxacin - - - -
Ofloxacin 0.5 2 0.5 5 23 23
Amikacin IE IE IE IE
Gentamicin IE IE IE IE
Netilmicin IE IE IE IE
Tobramycin IE IE IE IE
EUCAST Clinical Breakpoint Table v. 2.0, valid from 2012-01-01
S ≤ R > S ≥ R <
Ciprofloxacin 0.5
1. Low-level fluoroquinolone resistance (ciprofloxacin MICs of 0.12-0.5 mg/L) may occur but there is no evidence that this
resistance is of clinical importance in respiratory tract infections with H. influenzae .
2 Fluoroquinolones MIC breakpoint Disk Zone diameter Notes
(mg/L) content breakpoint (mm) Numbers for comments on MIC breakpoints
(µg)
Letters for comments on disk diffusion
0.5 5 26 26 2. Isolates with MIC values above the susceptible breakpoint are very rare or not yet reported. The identification and antimicrobial
susceptibility tests on any such isolate must be repeated and if the result is confirmed the isolate sent to a reference laboratory.
Until there is evidence regarding clinical response for confirmed isolates with MIC values above the current resistant breakpoint
they should be reported resistant.
1,2
Aminoglycosides
MIC breakpoint Disk Zone diameter
(mg/L) content
(µg)
breakpoint (mm)
S ≤ R > S ≥ R <
23 A A. The nalidixic acid disk diffusion test can be used to screen for fluoroquinolone resistance. Isolates with zone diameters ≥23 mm
can be reported susceptible to levofloxacin, ciprofloxacin, moxifloxacin and ofloxacin. Isolates with zone diameters