Antimicrobial susceptibility of 1,422 Haemophilus influenzae isolates from respiratory tract infections in Spain. Results of a 1-year (1996-97) multicenter surveillance study. Spanish Surveillance Group for Respiratory Pathogens.

A Haemophilus influenzae multicenter antimicrobial susceptibility surveillance was carried out. An overall beta-lactamase production rate of 25.7% was found, with significant differences between hospitals ranging between 7.9 and 47.9%. Presumable intrinsic resistance was found in 4.6% of strains. No differences in susceptibility were observed between beta-lactamase positive and beta-lactamase negative strains for all antibiotics, except for penicillin, amoxicillin and cefaclor. A higher prevalence of resistance was found for clarithromycin vs azithromycin (22.6 vs 0.7%). Differences in all these factors make surveillance essential as a guideline for empiric treatment in community-acquired respiratory tract infections.