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

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Abstract
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.