Study isolates. Flowchart showing selection and inclusion of bacterial isolates. aNORM 2007 surveillance population . bAccording to phenotypic susceptibility profiles (by gradient MIC, disk diffusion and beta-lactamase detection) as reported by the primary laboratories. The following selection criteria were used: amoxicillin-clavulanate MIC ≥2 mg/L, cefuroxime MIC ≥4 mg/L, cefotaxime MIC ≥0.12 mg/L and/or cefaclor 30 μg zone <17 mm (all isolates); and ampicillin MIC ≥1 mg/L, phenoxymethylpenicillin 10 μg zone <13 mm and/or ampicillin 2 μg zone <16 mm (beta-lactamase negative isolates). The selection criteria were constructed using epidemiological cut-off MIC values defined by EUCAST (http://www.eucast.org/MIC_distributions) and zone diameter distributions from the surveillance report . Information about the methodologies for susceptibility testing are included in the surveillance report . cOne beta-lactamase negative isolate from each laboratory, randomly selected from the isolates remaining after selection for the Resistant group. dMH-F, Mueller-Hinton agar supplemented with defibrinated horse blood and β-NAD for susceptibility testing of fastidious organisms (http://www.eucast.org). e
H. parainfluenzae (n = 3) and H. haemolyticus (n = 1).