We have proposed several strategies to preserve ciprofloxacin susceptibility: first, administering other antimicrobials (eg. cephalosporin) when patients have GNB infections and reserving ciprofloxacin as a second-line antibiotic; second, administering G-CSF in patients with profound neutropenia after intensive chemotherapy in order to reduce the neutropenic period, therefore, ciprofloxacin exposure might be reduced; third, antimicrobial prophylaxis with cefepime instead of ciprofloxacin for neutropenic patients requiring secondary prophylaxis. This evidence concerns the gene CSF3 and neutropenia.