Nosocomial pneumonia (NP) accounts for approximately 15% of all hospital-acquired infections. The incidence of NP rises in patients who are on breathing machines. The death rate for NP can be as high as 30%. NP caused by bacteria, such as Pseudomonas aeruginosa, has been associated with an increased death rate compared to other pathogens. Prompt use of appropriate antibiotics is essential. Compounding the issue of nosocomial infections is the increasing rate to which bacteria develop resistance to antibiotics. This hospital based trial is studying doripenem in patients who have nosocomial pneumonia to see if it is effective against bacteria associated with this serious bacterial infection. The duration of treatment can be anywhere from 8 to 14 days. Safety evaluations, such as vital signs and laboratory tests will be performed upon enrollment, after 4 days on therapy, after 9 days on therapy for those on greater than 8 days, at the end of therapy, 7 to 14 days after the end of therapy, and 28 to 35 days after the end of therapy. Adverse events will be collected throughout the study. Clinical response to doripenem therapy will be assessed 7 to 14 days after the end of therapy and the long-term clinical response to doripenem therapy will be assessed 28 to 35 days after the end of therapy. Doripenem IV will be administered for a duration of treatment from 8 to 14 days.