Introduction: The objective of this study was to assess the sensitivity of 400 strains of Haemophilus influenzae isolated in 21 Spanish laboratories in 1999 to 17 oral antibiotics.Methods. An agar dilution method in HT medium was used for sensitivity testing; interpretation of the results followed NCCLS criteria.
Results: Percentages of isolates susceptible to the antibiotics tested were as follows: ampicillin 59.5%, amoxicillin/clavulanate 99.2%, loracarbef 66.2%, cefprozil 70.2%, cefaclor 76.2%, cefuroxime 95%, ceftibuten 100%, cefpodoxime 100%, cefixime 100%, rifampin 99.8%, tetracycline 98.2%, chloramphenicol 99.2%, nalidixic acid 97.5%, ciprofloxacin 100%, trovafloxacin 100%, clarithromycin 74%, and azithromycin 100%.
Conclusions: Geographic distribution of sensitivity rates was not homogeneous for some antibiotics. Around 24% of strains were betalactamase producers, requiring higher MICs of antibiotics such as loracarbef, cefprozil and cefaclor than non betalactamase producers. Nevertheless MICs of ceftibuten, cefpodoxime and cefixime were similar in both betalactamase producers and non-producers. Five strains (1.25%) were beta -lactamase (2), but resistant to ampicillin (MIC > or = 8 mg/L) and to amoxicillin/clavulanic acid (MIC > or = 4/2 mg/L). Only three strains showed intermediate sensitivity to chloramphenicol. These strains and four others were inhibited with > or = 4 mg/L of tetracycline. Only one strain was resistant to tetracycline (MIC: 64 mg/L) and to rifampin (MIC: 256 mg/L). All strains were sensitive to azithromycin (MICs < or = 4 mg/L) and all were sensitive to ciprofloxacin and trovafloxacin (MICs < or = 0.5 mg/L). However, ten strains (2.5%) were resistant to nalidixic acid (MIC > or = 4 mg/L).