Efficacy and Safety of Cefepime/Nacubactam or Aztreonam/Nacubactam Compared to Imipenem/Cilastatin in Subjects With Complicated Urinary Tract Infections or Acute Uncomplicated Pyelonephritis

Inclusion Criteria:

1. Male or female patients at least18 years of age (or age of legal consent, whicheveris older) at the time of obtaining informed consent and who can be hospitalizedthroughout the Treatment Period;

2. Weight at most 140 kg;

3. Expectation, in the opinion of the Investigator, that the patient's cUTI or AP willrequire treatment with at least 5 days of IV antibiotics;

Exclusion Criteria:

1. Has a known imipenem- and/or meropenem-resistant Gram-negative uropathogen (at least 10^5 CFU/mL), isolated from study-qualifying urine culture; Note: If afterrandomization the susceptibility testing indicates resistance to imipenem and/ormeropenem, the patient may remain on the study drug at the Investigator'sdiscretion.

2. Has known or suspected single or concurrent infection with Acinetobacter spp. orother organisms that are not adequately covered by the study drug (eg, concurrentviral, mycobacterial, or fungal infection) and needs to be managed with otheranti-infectives; Note: Patients with qualifying pathogen coinfected with aGram-positive pathogen may be administered narrow spectrum, open-label glycopeptide (eg, vancomycin), oxazolidinone (eg, linezolid), or daptomycin concomitantly withthe study drug at the Investigator's discretion.

3. Has only a known Gram-positive primary uropathogen (at least 10^5 CFU/mL), isolatedfrom study qualifying urine culture;