Doripenem is an antibiotic medication not yet approved by the US FDA. This is a phase 3, multicenter, prospective, randomized, double-blind study of doripenem versus comparator antibiotic to assess the effectiveness and safety of doripenem in the treatment of complicated intra-abdominal infections in hospitalized adults. Doripenem or comparator is administered. The primary endpoint is the clinical response measured at late follow-up visit. The patients will receive either doripenem or comparator; treatment duration is 5 to 14 days.