Ceftriaxone therapy of group B streptococcal bacteraemia and meningitis in infant rats

The efficacy of ceftriaxone against group B streptococci was studied in vitro and in vivo with an infant rat model of group B streptococci bacteraemia and meningitis. Twenty-four strains demonstrated minimal inhibitory concentrations of ceftriaxone of 0.05−0.1 mg/1 and minimal bactericidal concentrations of 0.1−0.4 mg/1. Four strains were selected to induce bacteraemia and meningitis in infant rats by intraperitoneal inoculation. All 45 bacteraemic animals with or without meningitis that were treated with ceftriaxone 2 mg/kg/dose every eight hours for five doses survived, while all 12 control animals died (P≤000l). When recultured 54 h after the last dose of ceftriaxone, both CSF and blood remained sterile in all treated animals. These results indicate group B streptococci to be sensitive to ceftriazone in vitro and that, in the low dosage used, ceftriaxone effectively eradicates group B streptococcal bacteraemia and meningitis in infant rats.