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.