Beta-lactam antibiotic susceptibility of bacteria responsible for neonatal meningitis

Neonatal meningitis is caused by group B streptococci (GBS), Escherichia coli, and Listeria monocytogenes, in order of frequency. Newly developed cephalosporins with a broad spectrum of activity have altered the therapy of meningitis due to gram-negative bacilli. However, we found that clinical isolates of GBS and L. monocytogenes did not demonstrate uniform susceptibility to beta-lactam antibiotics. Antibiotic potencies for GBS tested were: cefotaxime, penicillin, ceftriaxone, amoxicillin, cefamandole, cephalothin, and moxalactam. N-formimidoyl thienamycin was most active for L. monocytogenes followed by penicillin, cephalothin and chloramphenicol; broad-spectrum cephalosporins were not active against Listeria organisms that were tested. These agents should not be utilized as solitary therapy of meningitis until the organism has been characterized with antibiotic susceptibilities.