Third-generation cephalosporin resistance among Gram-negative bacilli causing meningitis in neurosurgical patients: significant challenges in ensuring effective antibiotic therapy

Objectives: The treatment of meningitis caused by Gram-negative bacilli in neurosurgical patients is a major challenge because of the complexity of these patients, the emergence of antibiotic resistance in many of the causative organisms and the restricted choice of antibiotics suitable for use, owing to a failure to achieve high enough concentrations in the CSF. We reviewed the incidence, aetiology, treatment and outcome of all patients with Gram-negative bacillary meningitis (GNBM) in our centre over a 7 year period. Methods: Beaumont Hospital, Dublin is a 720 bed tertiary referral hospital and contains the national neurosurgical centre for the Republic of Ireland. The case notes and microbiological records of all patients with GNBM between 1998 and 2004 inclusive were reviewed retrospectively. Only patients with positive CSF culture and clinical features compatible with meningitis were included. Results: Forty separate episodes of GNBM involving 34 different patients occurred during the study period. The most common causative organisms were Enterobacter spp. (35%), Escherichia coli (22.5%) and Pseudomonas aeruginosa (15%). Twenty-five per cent of isolates were resistant to third-generation cephalosporins. The median duration of treatment was 19.2 days and a combination of intravenous and intraventricular antibiotics was the most common treatment regimen used. Mortality directly related to GNBM was 2.5%. Conclusions: Although the mortality directly related to GNBM was low, the emergence of strains resistant to third-generation cephalosporins represents a therapeutic challenge. Treatment with combined intravenous and intraventricular antibiotics is recommended for 2–3 weeks, but more studies are required to determine the optimal management of this difficult condition.