Determination of the in vivo post-antibiotic effects of ciprofloxacin and rifampicin

A modified rabbit meningitis model is described for determining the PAE in vivo, which utilised a self-standing device for repeatedly sampling pure CSF. The model allowed the PAEs of ciprofloxacin and rifampicin on Escherichia coli ATCC 25922 to be determined following PAE induction in vitro, or in vivo in CSF after intrathecal injection or during the last 1.5 h of a 7 h iv continuous infusion. The estimated volumes of distribution of ciprofloxacin and rifampicin in CSF were 0.68 +/- 0.24 mL and 0.74 +/- 0.04 mL, respectively, and the terminal elimination half lives were 1.8 +/- 0.5 h and 2.2 +/- 0.3 h, respectively. PAEs of approximately 2 h were obtained in vivo and in vitro after exposing E. coli to 3 x MIC of ciprofloxacin in vitro and to 1 x MIC of drug in vivo. When the organism was exposed to rapidly declining concentrations in vivo, only a minimal PAE was observed for both antibiotics. Moreover, a PAE of 3.1 +/- 1.3 h of rifampicin was obtained in vivo, being smaller than the 4.8 h PAE observed in vitro, which might be explained by the binding of 45 +/- 6.5% rifampicin to proteins in the CSF.

[Tuberculous meningitis]

The incidence of tuberculosis has been increasing since 1985. Favourable host factors associated with non specific neurologic abnormalities must lead to the hypothesis of a meningeal tuberculosis. Blood analysis and radiological findings rarely contribute to the diagnosis. The diagnosis is established when tubercle bacilli are identified in the cerebral-spinal-fluid, sometimes immediately but most often after 4 to 6 week culture. New faster methodes are being developed, but they are not yet routinely available. The treatment must be started before the identification of the tubercle bacilli. Usually, for immunocompetent patient, short-course treatment is chosen, consisting of an initial 2-month intensive treatment (rifampycin, isoniazid, and pyrazinamide) followed by a 4-month maintenance therapy with isoniadid and rifampicin, ethambutol should be included systematically during the first 16 weeks in prevention of isoniazid resistance.