Evaluation of Safety,Pharmacokinetics and Efficacy of CAZ-AVI With Metronidazole in Children Aged 3 Months to 18 Years Old With Complicated Intra-abdominal Infections (cIAIs).

1. Must be ≥3 calendar months to \<18 years of age. Patients aged ≥3 calendar months to \<1 year must have been born at term (defined as gestational age ≥37 weeks).

2. Written informed consent from parent(s) or other legally acceptable representative(s), and informed assent from patient (if age appropriate according to local regulations)

3. If female and has reached menarche, or has reached Tanner stage 3 development (even if not having reached menarche) (refer to Appendix E for further details on Tanner staging), the patient is authorised to participate in this clinical study if the following criteria are met:

At screening:

(i) Patient reports sexual abstinence for the prior 3 months or reports use of at least 1 of the acceptable methods of contraception, including an intrauterine device (with copper banded coil), levonorgestrel intrauterine system (eg, Mirena®), or regular medroxyprogesterone injections (Depo-Provera®); or (b) Patient agrees to initiate sexual abstinence from the time of screening until 7 days after end of treatment with study drug; and (ii) Patient is advised to avoid conception from the time of screening until 7 days after receipt of study drug and agrees not to attempt pregnancy from the time of screening until 7 days after end of treatment with study drug; and (iii) Patient is provided guidelines regarding continuation of abstinence, initiation of abstinence, or about allowed contraception; and (iv) Patient has a negative serum β-human chorionic gonadotropin (β-hCG) test just prior to study entry. Since serum tests may miss an early pregnancy, relevant menstrual history and sexual history, including methods of contraception, should be considered. Note: if the result of the serum β-hCG test cannot be obtained prior to dosing of investigational product, a patient may be enrolled on the basis of a negative urine pregnancy test, though a serum β-hCG test result must still be obtained.

4\. Must, based on the judgment of the Investigator, require hospitalisation initially and antibacterial therapy for 7 to 15 days in addition to surgical intervention for the treatment of the current cIAI 5. Require surgical intervention (eg, laparotomy, laparoscopic surgery or percutaneous drainage) to manage the cIAI 6. Must have clinical evidence of cIAI as follows: (i) Pre-operative enrolment inclusion:

1. Requires surgical intervention that is expected to be completed within 24 hours of enrolment Laparotomy, laparoscopy, or percutaneous drainage

2. Evidence of a systemic inflammatory response (at least 1): Fever (defined as oral temperature \>38.5°C, or equivalent to method used) or hypothermia (with a core body or rectal temperature \<35°C, or equivalent to method used) Elevated white blood cells (WBC) (\>15000 cells/mm3) C-reactive protein (CRP) levels (\>10 mg/L)

3. Physical Findings consistent with intra-abdominal infection, such as:

Abdominal pain and/or tenderness Localised or diffuse abdominal wall rigidity Abdominal mass

4. Intention to send specimens from the surgical intervention for culture

5. (Optional) Supportive radiologic findings of intra-abdominal infection, such as perforated intraperitoneal abscess detected on: Computed tomography (CT) scan or Magnetic resonance imaging (MRI) or Ultrasound (ii) Intra-operative/postoperative enrolment inclusion(in cases of postoperative enrolment, must be within 24 hours after the time of incision)::

Visual confirmation of intra-abdominal infection associated with peritonitis at laparotomy, laparoscopy or percutaneous drainage (to be confirmed pending feasibility); must have 1 of these diagnoses:

1. Appendiceal perforation or peri-appendiceal abscess

2. Cholecystitis with gangrenous rupture or perforation or progression of the infection beyond the gallbladder wall

3. Acute gastric or duodenal perforations, only if operated on \>24 hours after singular perforation occurs

4. Traumatic perforation of the intestines, only if operated on \>12 hours after perforation occurs

5. Secondary peritonitis (but not spontaneous bacterial peritonitis associated with cirrhosis and chronic ascites)

What this study is about