Safety and Efficacy Study to Compare IV CXA 101/Tazobactam and Metronidazole With Meropenem in Complicated Intraabdominal Infections

Inclusion Criteria: * Male or female, from 18 to 90 years of age, inclusive * One of the following diagnoses (in which there is evidence of intraperitoneal infection) including:(a) Cholecystitis (including gangrenous cholecystitis) with rupture, perforation, or progression of the infection beyond the gallbladder wall;(b)Diverticular disease with perforation or abscess; (c) Appendiceal perforation or periappendiceal abscess; (d) Acute gastric or duodenal perforation, only if operated on \>24 hours after perforation occurs; (e) Traumatic perforation of the intestine, only if operated on \> 12 hours after perforation occurs; (f) Peritonitis due to perforated viscus, postoperative or spread from other focus of infection (but not spontaneous \[primary\] bacterial peritonitis or peritonitis associated with cirrhosis and chronic ascites).Subjects with inflammatory bowel disease or ischemic bowel disease are eligible provided there is bowel perforation; or (g) Intraabdominal abscess (including liver and spleen). * Subject requires surgical intervention (e.g. laparotomy, laparoscopic surgery, or percutaneous draining of an abscess) within 24 hours of (before or after) the first dose of study drug * If subject is to be enrolled preoperatively, the subject must have radiographic evidence of bowel perforation or intraabdominal abscess * Subjects who failed prior antibacterial treatment for the current cIAI can be enrolled but must: (a) have a positive culture (from an intraabdominal site) and (b) require surgical intervention. Such subjects can be enrolled before the results of the culture are known; however, if the culture is negative, study drug administration must be discontinued. * Willing and able to comply with all study procedures and restrictions * Willing and able to provide written informed consent Exclusion Criteria: * Women who are pregnant, nursing, or - if of child bearing potential - not using a medically accepted, effective method of birth control (e.g. condom, oral contraceptive, indwelling intrauterine device, or sexual abstinence) * Diagnosis of abdominal wall abscess; small bowel obstruction or ischemic bowel disease without perforation; traumatic bowel perforation with surgery within 12 hours; perforation of gastroduodenal ulcer with surgery within 24 hours (these are considered situations of peritoneal soiling before infection has become established); another intraabdominal process in which the primary etiology is not likely to be infectious. * Simple cholecystitis, gangrenous cholecystitis without rupture, simple appendicitis, acute suppurative cholangitis, infected, necrotizing pancreatitis, or pancreatic abscess * cIAI managed by staged abdominal repair (STAR), open abdomen technique or any situation where infection source control is not likely to be achieved * Known prior to randomization to have an IAI or postoperative infection caused by pathogen(s) resistant to meropenem * Considered unlikely to survive the 4- to 5-week study period * Any rapidly-progressing disease or immediately life-threatening illness (including acute hepatic failure, respiratory failure and septic shock) * The need for concomitant systemic antibacterial agents (other than vancomycin or linezolid) in addition to study drug(s) * Moderate or severe impairment of renal function (estimated CrCl \< 50 mL/min), or requirement for peritoneal dialysis, hemodialysis or hemofiltration, or oliguria (\< 20 mL/h urine output over 24 hours) * The presence of hepatic disease defined as: (a) ALT or AST \> 4 x ULN; (b)Total bilirubin \>2 x ULN, unrelated to cholecystitis (c) Alkaline phosphatase \>4 x ULN. Subjects with a value \>4 x ULN and \<5 x ULN are eligible if this value is historically stable. * Subjects with acute hepatic failure or acute decompensation of chronic hepatic failure * Hematocrit \< 25% or hemoglobin \< 8 gm/dL * Neutropenia with absolute neutrophil count \< 1000/mm3 * Platelet count \< 75,000 /mm3. Subjects with a platelet count as low as 50,000 /mm3 are permitted if the reduction is historically stable. * Immunocompromising illness, including known human immunodeficiency virus (HIV) positivity or AIDS, organ (including bone marrow) transplant recipients, and hematological malignancy. Immunosuppressive therapy, including use of high-dose corticosteroid therapy (e.g. \>40 mg prednisone or equivalent per day for greater than 2 weeks). * History of hypersensitivity reactions to cephalosporins, carbapenems, penicillins, ß-lactamase inhibitors, metronidazole, or nitroimidazole derivatives. Subjects with a history of mild skin rash, not documented to be caused by previous ß-lactam use, may be enrolled. * Any condition or circumstance that, in the opinion of the Investigator, would compromise the safety of the subject or the quality of study data * Clinically significant abnormality in baseline electrocardiogram (ECG) * Participation in any investigational drug or device study within 30 days prior to study entry * Use of systemic antibiotic therapy for IAI for 24 or more hours in the 48-hour period prior to the first dose of study drug, unless there is a documented treatment failure with such therapy * More than one dose of an active non-study antibacterial regimen was given postoperatively. For subjects enrolled preoperatively, no postoperative non-study antibacterial therapy is allowed * who previously participated in a study with CXA-101 * Subjects who previously received imipenem, meropenem, doripenem or cefepime for the current intraabdominal infection * Subjects who have received disulfiram in the past 14 days or who are currently receiving probenecid.