Antibiotic Susceptibility of Type b Haemophilus influenzae and Streptococcus pneumoniae, and Antibiotic Concentration in Cerebrospinal Fluid

Antibiotic susceptibilities of 38 type b Haemophilus influenzae and 28 Streptococcus pneumoniae strains isolated from cerebrospinal fluid, blood and other specimens between 1973 and 1988 were studied. Minimal inhibitory concentrations (MICs) of ampicillin against 10 β-lactamase positive and 28 negative H. influenzae isolates were 32–64 and 0.25 μg/ml, respectively. The MIC of chloramphenicol against one of the β-lactamase positive H. influenzae strains was 8 but MICs against the rest of the organisms were 0.5–1 μg/ml. MICs of cefotaxime, ceftriaxone and cefuroxime against all H. influenzae strains were 0.016, 0.008 and 0.5 μg/ml, respectively. No S. pneumoniae isolates were resistant to penicillin G and MICs of this drug were 0.016–0.032 μg/ml. MICs of cefotaxime, ceftriaxone and cefuroxime against all S. pneumoniae strains were 0.016–0.032, 0.016–0.032 and 0.032–0.063 μg/ml, respectively. MICs of chloramphenicol against 15, 4 and 9 of S. pneumoniae isolates were 2, 8 and 16 μg/ml, respectively. Antibiotic concentrations in the cerebrospinal fluid of patients with bacterial meningitis after intravenous administration of ampicillin (50–70 mg/kgx4/day), penicillin G (31–63 mg/kgx4/day), cefotaxime (50 mg/kgx4/day) and chloramphenicol (25 mg/kgx4/day) were 4.70±1.83 (n=11), 0.57±0.32 (n=7), 4.97±2.60 (n=9) and 8.52±3.54 μg/ml (n=3), respectively. The initial choice of antibiotics in older children with bacterial meningitis is a combination of ampicillin (75 mg/kgx4/day) and cefotaxime (50 mg/kgx4/day) to cover ampicillin-resistant H. influenzae, S. pneumoniae, and Listeria monocytogenes in Japan. These antibiotics should be changed according to the causative organisms and their antibiotic susceptibilities.