Distribution and resistance patterns of Haemophilus influenzae: a European cooperative study

The first European survey of the prevalence of antibiotic resistance in Haemophilus influenzae was conducted between February and October 1986. Eighty laboratories in nine countries participated (Austria, Belgium, France, FRG, The Netherlands, Spain, Sweden, Switzerland and the UK). A total of 1,961 clinical isolates was examined for type b encapsulation, beta-lactamase production and susceptibility to ampicillin, chloramphenicol, cefaclor, erythromycin and tetracycline, using a unique microdilution method. The proportion of isolates resistant to these antibiotics varied considerably between individual countries. The highest prevalence of ampicillin resistance was found in Spain (30.6%), and the lowest in the FRG (1.6%), with a mean value of 10% for all countries. Chloramphenicol resistance was highest in Spain (24.9%) and Belgium (10.9%) and lowest in The Netherlands (0.6%) and Austria (0.5%), with a mean value of 4.7%. Resistance to erythromycin ranged from 27% of the isolates in The Netherlands to 1.1% in Austria. For tetracycline, values ranged from 1.5% in the UK to 17.8% in Belgium and 25.4% in Spain. The lowest mean prevalence of resistance was observed for cefaclor (breakpoint 8 mg/l): 5% or less in all countries. These inter-country differences could only partially be explained by variations in the proportion of type b strains, the source of the isolates and the mode of collection.