Antibiotic susceptibility of Haemophilus influenzae isolated from cerebrospinal fluid and blood.

The emergence of ampicillin and chloramphenicol resistant Haemophilus influenzae type b in Denmark has created demands for alternative treatments of serious infections with H. influenzae. In this study 102 strains of H. influenzae recovered from cerebrospinal fluid (85) and blood (17) were tested for susceptibility to ampicillin, piperacillin, erythromycin, rifampicin, chloramphenicol, cefuroxime, cefotaxime, ceftazidime, ceftriaxone, moxalactam, aztreonam, and netilmicin by means of the agar dilution method. The majority (97%) was H. influenzae type b and of these strains 94% belonged to biotype I. Nine of the investigated strains were beta-lactamase producers. Ceftriaxone and cefotaxime were the most active agents (MIC90 less than or equal to 0.025 microliter/ml) followed by moxalactam and aztreonam (MIC90 = 0.1 microgram/ml). Except for ampicillin and piperacillin, the MIC was similar for beta-lactamase producers and non-producers. Several of the investigated antibiotics, especially some of the third generation cephalosporins, might constitute valid therapeutical alternatives to conventional drugs in the treatment of severe H. influenzae infections.