Patient description: The patients is a 25-year-old G1 P1 pregnant woman who is 24W3D gestational old who developed a sudden unset of fever and chills, accompany with nausea and vomiting. She also complains of dysuria, urgency and frequency. She also reports some severe pain in the flank. Her vital signs are: T = 39.7ºC, P = 117, R = 20, and BP = 113/74 mm Hg. Physical examination reveals tenderness on palpation of both costovertebral angles. She has no history of recurrent UTI prior to her pregnancy or any other underlying disease. The urine culture showed Gram-negative rod-shaped bacterial cells, leukocytes, and leukocyte casts. The blood culture is negative. A CBC shows Hb 12.9 g/dL, Hct 39%, MCV 76 fL, WBC count 14,120/µL.

Clinical trial eligibility criteria: eligible ages (years): 18.0-99.0,  Urinary Tract Infection Have documented clinical signs and/or symptoms of complicated urinary tract infection (cUTI) at diagnosis*. *Clinical signs and symptoms of cUTI either: 1. Pyelonephritis, as indicated by at least 2 of the following Documented fever (temperature greater than 38 degrees Celsius) accompanied by symptoms of rigors, chills, or "warmth" Flank pain Costovertebral angle tenderness on physical exam Nausea or vomiting Dysuria, urinary frequency, or urinary urgency OR 2. Complicated lower UTI, as indicated by at least 2 of the following new or worsening symptoms of cUTI Dysuria, urinary frequency, or urinary urgency Documented fever (temperature greater than 38 degrees Celsius) accompanied by symptoms of rigors, chills, or "warmth" Documented hypothermia (temperature less than 35.5 degrees Celsius) Suprapubic pain or pelvic pain  Have a documented history of any moderate or severe hypersensitivity or allergic reaction to all five oral therapy options. 2. Have a concomitant infection at the time of randomization, which requires non-study systemic antibacterial therapy effective against complicated Urinary Tract Infection (cUTI) in addition to study drug. 3. Have received more than 48 hours of a potentially therapeutic antibiotic for treatment of the current cUTI within 72 hours before randomization*. *Except if the following apply: 1. The subject has a known baseline urinary pathogen (urine culture positive) and has failed prior therapy clinically (persistence of criteria) AND 2. The pathogen is known to be non-susceptible to the previous therapeutic regimen used or the urine culture remains positive with a density of greater than or equal to 50,000 CFU/mL or greater than or equal to 10,000 for catheterized patients. 4. Women breastfeeding or donating breast milk. 5. Have intractable UTI infection at baseline that the investigator anticipates would require more than 7 days of study drug therapy. 6. Have complete, permanent obstruction of the urinary tract*. *Patients with complete permanent obstruction expected to be medically or surgically treated prior to End of Treatment (EOT) are eligible. 7. Have confirmed fungal UTI at time of randomization (with greater than or equal to 10^3 fungal CFU/mL). 8. Have suspected or confirmed perinephric or intrarenal abscess. 9. Have suspected or confirmed prostatitis, epididymitis. 10. Have an ileal loop or known vesico-ureteral reflux. 11. Have a current urinary catheter that is not scheduled to be replaced before EOT*. *Intermittent straight catheterization or replacement of new nephrostomy catheters is acceptable. 12. Have planned inpatient urological intervention(s) for suspected infected kidney stone or any other planned urological procedure with anticipated antibiotic prophylaxis between randomization and End of Treatment (EOT). 13. Have bacteremia with a uropathogen causing cUTI. 14. Have an estimated or calculated Creatinine Clearance (CrCl) less than or equal to 20 mL/min or currently receiving hemo or peritoneal dialysis at screening. 15. Have any condition or circumstance that, in the opinion of the investigator, would compromise the safety of the subject or the quality of study data*. *Including any rapidly progressing disease or immediately life-threatening (acute hepatic failure, respiratory failure or septic shock). 16. Have participated in any interventional trial of an investigational product within 30 days before the proposed first day of study drug administration. 17. Plans to participate or currently enrolled in any interventional study of an investigational agent for the duration of the trial. 18. Previous randomization in this trial. 19. Any recent (less than 4 weeks) history of trauma to the pelvis or urinary tract. 20. Prior fosfomycin use in the past 12 months