Inclusion Criteria

DISEASE CHARACTERISTICS:

- Patients must fit 1 of the following categories:

- Chemotherapy patients

- Scheduled to receive at least 2 consecutive courses (not required to be the
first 2 courses) of intensive chemotherapy for de novo, relapsed, or
secondary acute myeloid leukemia (AML), or relapsed acute lymphoblastic
leukemia (ALL)

- For the purposes of this study, "intensive chemotherapy" is defined as
regimens that are predicted by the local Investigator to cause neutropenia
for > 7 days including, but not limited to:

- Treatment with "4-drug induction" (anthracycline, vincristine,
asparaginase, and steroid)

- High-dose cytarabine, anthracycline/cytarabine, or
ifosfamide/etoposide

- Clofarabine-containing regimens

- Stem cell transplantation patients*

- Scheduled to receive at least 1 myeloablative autologous or allogeneic
hematopoietic stem cell transplantation (HSCT)

- For the purposes of this study, myeloablative autologous and allogeneic
HSCT are those in which the conditioning regimen is predicted by the local
Investigator to cause neutropenia for > 7 days NOTE: *Patients with AML or
ALL who were enrolled on this study during intensive chemotherapy are not
eligible to be enrolled during HSCT.

PATIENT CHARACTERISTICS:

- ECOG performance status 0-2

- Creatinine clearance or radioisotope GFR > 70 mL/min OR serum creatinine based on age
and/or gender as follows:

- 0.5 mg/dL (6 months to < 1 year of age)

- 0.6 mg/dL (1 to < 2 years of age)

- 0.8 mg/dL (2 to < 6 years of age)

- 1.0 mg/dL (6 to < 10 years of age)

- 1.2 mg/dL (10 to < 13 years of age)

- 1.5 mg/dL (male) or 1.4 mg/dL (female) (13 to < 16 years of age)

- 1.7 mg/dL (male) or 1.4 mg/dL (female) (≥ 16 years of age)

- No patients with an allergy to quinolones

- No patients with chronic active arthritis

- No patients with a known pathologic prolongation of the QTc

- No females who are pregnant or breast feeding

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- No patients scheduled to receive non-intensive or palliative chemotherapy

- No patients undergoing non-myeloablative hematopoietic stem cell transplantation
(HSCT)

- No patients being treated with antibacterial agents, other than cotrimoxazole for
Pneumocystitis jiroveci (PCP) prophylaxis