A Trial of Fosfomycin vs Ciprofloxacin for Febrile Neutropenia

Inclusion Criteria: 1. Subjects who are able to understand study procedures, comply with them, and provide written informed consent before any study-specific procedure. 2. Adult subjects ≥ 18 years of age with acute leukemia diagnosis who are going to receive their first intensive chemotherapy cycle or adult subjects ≥ 18 years of age who are candidates to receive a first stem cell transplant. 3. Expected neutropenia 100x109/L lasting at least seven days. In case of expected neutropenia range 100-500x109/L lasting seven days or more, at least one of the following risk factors for infection must be present: 1. Performance status (Eastern Cooperative Oncology Group, ECOG) ≥2. 2. Expected mucositis grade 3-4. 3. Age ≥65 years. 4. Comorbidity Index (HCTI) ≥3. 5. Serum albumin\< 35 g/L. 6. Total dose of etoposide \> 500 mg/m2 7. Total dose of cytarabine \> 1 g/m2 8. Active or refractory neoplasia at the moment of stem cell transplant. 4. Performance status (Eastern Cooperative Oncology Group, ECOG) of 0 to 3. 5. Adequate organ function defined as: Liver: bilirubin, alkaline phosphatase, or SGOT \< 3 times the upper normal limit (unless it is attributable to tumor activity). Renal : creatinine ≤ 250 μmol/l (2.5 mg/dL) (unless it is attributable to AML activity). 6. Life expectancy higher than 3 months. 7. Women of child-bearing potential must not be pregnant or breastfeeding and must have a negative pregnancy test at screening. Women of child-bearing potential and men with female partners of child-bearing potential must agree to practice 2 highly effective contraceptive measures of birth control and must agree not to become pregnant or father a child while receiving any study therapy and for at least 3 months after completing treatment. Exclusion Criteria: 1. Hypersensitivity to fluoroquinolones or fosfomycin. 2. Treatment with broad spectrum antimicrobial therapy within 4 weeks of first study treatment. 3. Prior Intensive chemotherapy or stem cell transplant. Treatment with hydroxyurea or corticosteroids used to control white blood cell counts are permitted. 4. Fever of infectious origin or documented infection within 4 weeks of first study treatment. 5. Presence of any severe psychiatric disease or physical condition that, according to the physicians criteria, contraindicates the inclusion of the patient into the clinical trial. 6. Subjects that have participated previously in this study