Antimicrobial susceptibility of 840 clinical isolates of Haemophilus influenzae collected in four European countries in 2000-2001

In 2000-2001, 840 clinical isolates of Haemophilus influenzae were collected from laboratories in France, Germany, Italy and Spain (210 isolates/country). β-Lactamase production among the isolates varied considerably by country, ranging from 8.1 % in Germany to 34.8% in France. H. influenzae from patients ≤4 years old showed the highest prevalence of β-lactamase production (23.2%), compared with isolates from patients aged 5-17 years (17.8%) and ≥18 years (16.5%). All isolates were susceptible to amoxicillin-clavulanate, ciprofloxacin and levofloxacin; 99.6% and 98.9% of isolates were susceptible to azithromycin and cefuroxime, respectively. Among the macrolides tested, azithromycin (MIC90, 2 mg/L) was eight-fold more potent than clarithromycin (MIC90, 16 mg/L) and roxithromycin (MIC90, 16 mg/L). Despite variations in β-lactamase production between different countries, >99% of all isolates were susceptible to amoxicillin-clavulanate, ciprofloxacin, levofloxacin, and azithromycin