Modulation of efficacies and pharmacokinetics of antibiotics by granulocyte colony-stimulating factor in neutropenic mice with multidrug-resistant Enterococcus faecalis infection

It has been demonstrated previously that, in non-neutropenic animals, inter feron-gamma markedly enhances the efficacies of gentamicin and vancomycin a gainst Enterococcus faecalis resistant to these antibiotics. The aim of our study was to determining whether granulocyte colony-stimulating factor (G- CSF) can be beneficial as an adjunct to gentamicin and vancomycin in the tr eatment of the same infection in neutropenic mice. After induction of neutr openia by cyclophosphamide, mice were inoculated ip with the organism. The infected animals received sc administrations of G-CSF, antibiotic or a comb ination of both agents at determined dosing regimens. Infected animals trea ted with G-CSF alone showed a dose-dependent increase in survival. The inoc ulum size used in establishing infection affected the effectiveness of the cytokine. Survival was significantly (P < 0.01) better in the infected anim als given gentamicin and vancomycin plus G-CSF than in those given antibiot ics or G-CSF alone. The possibility of pharmacokinetic interaction between G-CSF and each of the antibiotics was examined. The cytokine significantly increased the plasma clearance of gentamicin, with a resultant decrease in the area under the concentration-time curve (AUC), while the disposition of vancomycin was not affected. This study suggests that G-CSF may be a usefu l adjunct to gentamicin and vancomycin for the treatment of multidrug-resis tant E. faecalis infection in neutropenic patients.