The purpose of the study is to compare the safety and effectiveness of the antibiotic levofloxacin by administering a higher dose of levofloxacin using a shorter course of therapy to treat patients with infections of their kidney.

The goal is to complete a pilot study of short course (5 days), high dose, levofloxacin treatment for women with acute uncomplicated pyelonephritis. Specific study objectives include:

1. To assess the efficacy and tolerability of levofloxacin 750 mg once daily for treatment of acute uncomplicated pyelonephritis in 25 women.
2. To describe the population pharmacokinetics of levofloxacin 750 mg once daily in treatment of young women with acute pyelonephritis.
3. To identify urine proteins associated with the inflammatory response of acute pyelonephritis, and characterize the time course of resolution of these proteins following initiation of treatment.

Inclusion criteria:

• Recent onset (less than 7 days) of costovertebral angle pain or tenderness with or without fever, and with or without lower urinary tract symptoms (dysuria, frequency, urgency). Diabetic women without long term complications of diabetes (retinopathy, nephropathy, or neuropathy) may be enrolled.
• Stable hemodynamic status and able to tolerate oral medication.
• Pretherapy urine culture >107 cfu/L (>104 cfu/ml) of a uropathogen (E. coli, other Enterobacteriaceae, S. saprophyticus). Patients will be enrolled into the study prior to urine culture results being known. If pretherapy cultures are subsequently not positive (usually at 48 hours), subjects will be discontinued.
• Pyuria (> 10 wbc/mm3 or > 10 X106 wbc/L by hemocytometer; > 6-10 wbc/hpf, or > 1+ LE (leukocyte esterase) dipstick).

Exclusion Criteria:

·Pregnancy, breastfeeding, fluoroquinolone allergy, and any underlying structural or functional genitourinary abnormality.