Observed lower cure rates and higher mortality rates in one of the treatment groups.

The purpose of this study is to show that doripenem is as effective as imipenem-cilastatin in the treatment of patients with ventilator-associated pneumonia.

This is a randomized (the study medication is assigned by chance), double-blind (neither physician nor patient knows the treatment that the patient receives), active-controlled (agent that is compared with a study medication to test whether the study medication has a real effect in a clinical study), double-dummy (placebo [inactive substance that is compared with a medication to test whether the medication has a real effect in a clinical study] is administered to maintain the blind when the comparator medication cannot be made identical to the study medication), parallel-group (each group of patients will be treated at the same time), multicenter study to assess the effectiveness and safety of 7 day course of doripenem, compared with 10 day course of imipenem-cilastatin in patients with ventilator-associated pneumonia. This study will consists of 3 phases: (1) a pretreatment phase with a maximum of 24 hours for the screening/baseline visit, (2) a double blind, double dummy, treatment phase of 10 days (Day 1 to Day 10) and an end-of-treatment (EOT) assessment within 24 hours after the last dose of study medication therapy administered on Day 10 or at the time of early withdrawal from study medication, and (3) a post treatment (follow-up) phase consisting of an early follow-up (EFU) visit within 7 to 14 days after the last dose of study medication, and last follow-up (LFU) visit within 28 to 35 days after the last dose of study medication for all patients including those who discontinued study medication early. Two hundred and seventy four patients will be randomly assigned to receive either doripenem or imipenem with placebo of the other medication given simultaneously to maintain the blind (eg, 1 group will receive blinded doripenem from Days 1 to 7 and imipenem placebo Days 1 to 10, other group will receive blinded imipenem Days 1 to 10 and doripenem placebo Days 1 to 7). A sample of secretions from the lower respiratory tract will be obtained by bronchoalveolar lavage (BAL) or mini-BAL within 36 hours prior to administration of study medication from the enrolled patients and sent for culture. Patients, whose baseline BAL or mini-BAL culture results will yield at least 1 qualifying pneumonia pathogen will continue to receive study medication therapy and patients, whose baseline BAL or mini-BAL culture results did not yield at least 1 qualifying pneumonia pathogen will be discontinued from study medication therapy but will remain enroll in the study and will be followed for safety. Safety evaluations including adverse events, clinical laboratory evaluations, vital signs and physical examinations will be monitored throughout the study period. The total duration of an individual patient's participation in the study will be approximately 5 to 6 weeks.

Inclusion Criteria:

• Patients must have new or worsening radiographic infiltrates consistent with ventilator-associated pneumonia that was not related to cardiac or other disease processes
• Have at least 1 of the following: fever (core body temperature greater than 39.0°C); hypothermia (core body temperature of less than 35.0°C); leukocytosis (increased WBC count); and leukopenia (decreased WBC count)
• Have developed ventilator-associated pneumonia and have been on mechanical ventilation for more than or equal to 48 hours and on mechanical ventilation at the time that study medication is assigned
• Have been hospitalized or been in a chronic care facility for consecutive 5 days or more within the last 90 days
• Have a baseline Clinical Pulmonary Infection Score (CPIS) more than or equal to 6 and an Acute Physiology and Chronic Health Evaluation (APACHE) II score more than 8 and less than 35

Exclusion Criteria:

• Have received antibiotics for this episode of ventilator-associated pneumonia for more than 24 hours before study medication administration
• Known presence at baseline of only methicillin-resistant Staphylococcus aureus or Stenotrophomonas infection
• Acute respiratory distress syndrome
• Has any of the following conditions: chest trauma with severe lung bruising or loss of stability of the thoracic cage following a fracture of the sternum, ribs, or both, increased amounts of fluid in the lung cavities requiring drainage or pus in the cavity
• Has active seizure disorder within the last 2 years or brain injury such that imipenem cilastatin would not be administered to the patient in usual practice
• Has lung cancer within the last 2 years, chronic bronchitis with an increase in severity within the last 30 days, chronic enlargement of the bronchi or bronchioles related to inflammatory disease or obstruction, lung abscess(s), anatomical bronchial obstruction, respiratory tuberculosis on treatment, suspected atypical pneumonia, chemical pneumonitis, cystic fibrosis, congestive heart failure, severe burns to greater than 15% of the body, evidence of severe and chronic liver disease