Should we reconsider cefazolin for treating staphylococcal meningitis? A retrospective analysis of cefazolin and cloxacillin cerebrospinal fluid levels in patients treated for staphylococcal meningitis.

OBJECTIVES: To assess the meningeal penetration of cefazolin and cloxacillin in individuals treated for methicillin-susceptible staphylococcal meningitis. METHODS: We retrospectively identified individuals treated for Staphylococcus meningitis with measurements of cefazolin or cloxacillin concentrations in cerebrospinal fluid (CSF) using a validated assay of liquid chromatography coupled with mass spectrometry at the Nantes University Hospital between January 2009 and October 2019. Staphylococcus meningitis was defined by a compatible clinical presentation and a microbiological confirmation (positive CSF culture or positive specific PCR). Medical charts were retrospectively reviewed to collect microbiological and clinical data, and to assess therapeutic success. RESULTS: Among the 17 included individuals, eight (47%) were treated with cefazolin and nine (53%) with cloxacillin. Median daily dosages of cefazolin and cloxacillin were 8 g (range 6-12 g) and 12 g (range 10-13 g), respectively. Cefazolin and cloxacillin were mainly administered by continuous infusion. Eleven individuals (65%) were men, median (interquartile range (IQR)) age was 54 years (50; 70), 14 (82%) had postoperative meningitis and 3 (18%) had haematogenous meningitis. Median (IQR) antibiotic CSF concentrations were 2.8 mg/L (2.1; 5.2) and 0.66 mg/L (0.5; 0.9) for cefazolin and cloxacillin groups, respectively. Cloxacillin was discontinued in two individuals for therapeutic failure. CONCLUSIONS: Patients with staphylococcal meningitis treated with high-dose continuous intravenous infusion of cefazolin achieved therapeutic concentrations in CSF. Cefazolin appears to be a therapeutic candidate that should be properly evaluated in this indication.

The passage of cloxacillin into cerebrospinal fluid in the absence of meningitis.

1. Eleven patients undergoing lumbar discectomy received cloxacillin by continuous i.v. infusion, starting before the operation. During the operation several blood samples and one CSF sample were taken. 2. Mean rate constants describing the passive transfer of drug from plasma to CSF (kp) and the largely active transfer in the opposite direction (kCSF) were estimated. 3. In some subjects the CSF albumin quotient, defined as the ratio between the albumin concentration in CSF and in plasma times 1000, was slightly elevated (up to 23) which caused a significant increase in the value of kp. 4. The estimate of mean kp for healthy individuals was 0.065 h-1, which corresponds to a half-life of 10 h. The estimate of mean kCSF was 2.10 h-1. This predicts a steady-state CSF drug concentration which is 3% of the unbound plasma drug concentration. 5. There was a significant lag between the time courses of plasma and CSF drug concentrations, presumably reflecting the time for drug to move from the choroid plexus to the lumbar sampling site. 6. Four other patients received cloxacillin for prophylactic or therapeutic reasons by continuous i.v. infusion. In three of those patients the albumin quotient was normal or slightly elevated and the steady-state CCSF/Cu ratio was similar to the predicted normal value. 7. These findings indicate that eradicating staphylococci from CSF in cases of meningitis with a low degree of inflammation may be difficult.