The present study is a retrospective cohort study on patients who suffered a nosocomial infection in major hospitals in Vietnam. Data relating to patient demography include age, gender; medical history; APACHE II score; background conditions, infection details and antimicrobial therapy; and all-caused mortality, time of hospitalization and intensive care. The investigators hypothesis is that antimicrobial treatment inappropriate is highly dependent on incidence of antibiotic resistant pathogens, nonfermentative Gram-negative bacilli and ESBL-producing enterobacteriaceae spp. Variables are demographic characteristics, background conditions, immunosuppressive therapy, antimicrobial susceptibility and inappropriate treatment is explored as possible predictors of mortality.

Inclusion Criteria:

• Patient was diagnosed as nosocomial infection defined according to criteria established by the US CDC. The diagnosis criteria for ventilator-associated pneumonia are modified from those established by the American College of Chest Physicians.
• Patient received empiric antimicrobial therapy within 24 hour from onset of infection and had antimicrobial susceptibility.

Exclusion Criteria:

• A patient was in part of a controlled clinical trial for the current infection episode.
• Patients with suspected infections by virus or fungus or tuberculosis will be excluded.

Patient was diagnosed as nosocomial infection