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): 18.0-70.0,  Urinary Tract Infection Is a man or woman aged 18 to 70 years, inclusive. 2. Has pyuria (a white blood cell [WBC] count greater than 10/μL in unspun urine or greater than or equal to 10 per high power field in spun urine). 3. Has clinical signs and/or symptoms of a complicated lower urinary tract infection (UTI) and/or acute pyelonephritis that one or more of the following: fever (i.e, axillary temperature greater than 37.7°C), chills, malaise, flank pain, back pain, and/or costo-vertebral angle pain or tenderness and/or any symptoms of dysuria (dysuria, urinary urgency, urinary frequency, suprapubic discomfort, new urinary incontinence or worsening of pre-existing incontinence) that occur in the presence of a functional or anatomical abnormality of the urinary tract or in the presence of catheterization. 4. Has a pretreatment baseline urine culture specimen obtained within 24 hours before the administration of the first dose of study drug (NOTE: Participants may be enrolled in this study and start intravenous (IV) study drug therapy before the Investigator knows the results of the baseline urine culture). 5. Requires IV antibacterial therapy for the treatment of the presumed complicated UTI (cUTI). 6. In the opinion of the investigator, is capable of understanding and complying with protocol requirements. 7. Signs and dates a written, informed consent form and any required privacy authorization prior to the initiation of any study procedures, or has a legally acceptable representative sign the forms. 8. Meets protocol-specified regarding the use of contraception; and 9-Is willing and able to comply with study procedures  Has received any investigational compound within 30 days of screening. 2. Is an immediate family member, study site employee, or is in a dependent relationship with a study site employee who is involved in the conduct of this study (eg, spouse, parent, child, or sibling) or may consent under duress. 3. Is a female participant who is pregnant or lactating or intending to become pregnant before, during, or within one month after participating in this study, or intends to donate ova during such time period. 4. Is a male participant who intends to donate sperm during the course of this study or for 12 weeks thereafter. 5. Has participated in another clinical study within the past 30 days. 6. Has a history of allergy to or intolerance of beta-lactams (penicillins, cephalosporins or carbopenems). 7. Has signs, symptoms or history of any condition that, per protocol or in the opinion of the investigator, might compromise: 1) the safety or well-being of the participant or study staff, 2) the safety or well-being of the participant's offspring (such as through pregnancy or breast-feeding), or 3) the analysis of results. 8. Has received any amount of potentially therapeutic antibacterial therapy after collection of the pretreatment baseline urine culture and before administration of the first dose of study drug. 9. Has received any dose of a potentially therapeutic antibacterial agent for the treatment of the current UTI within 48 hours before providing the pretreatment baseline urine culture specimen. 10. Has a current urinary catheter that is not scheduled to be removed before the End-of-Therapy (EOT) visit (intermittent straight catheterization during the IV study drug administration period is acceptable). 11. Has any history of trauma to the pelvis or urinary tract within one year before the screening visit. 12. Has any other contraindications to the medicines that are to be used in the study (according to the manufacturer's instructions). 13. Is considered unlikely to survive the four-week study period or has any rapidly progressing disease or immediately life-threatening illness (including acute hepatic failure, respiratory failure or septic shock)