Recently clinical guidelines categorize pneumonia in to three types: community, healthcare-associated, and hospital-acquired. Much of the existing research to describe the epidemiology of pneumonia in critically ill patients comes from single-center studies or from retrospective database analyses, which limit generalizability and lead to over-prescription of broad-spectrum antibacterial agents. This will be a prospective, multicenter epidemiological study to characterize pneumonia epidemiology in critically ill adult patients.

Pneumonia is one of the leading causes of death in the United States and is associated with significant costs to the healthcare system. Recent treatment guidelines describe a new subtype of pneumonia, healthcare-associated pneumonia (HCAP), to identify those patients who present to a hospital from the community and are thought to be at greater risk for developing pneumonia due to multidrug resistant organisms (MDRO).

The HCAP categorization scheme is intended to improve the prescription of initial appropriate empiric antibacterial agents and minimize the morbidity and mortality associated with inappropriate empiric selection.However, one of the chief criticisms of the guideline recommendations is that the criteria used to define HCAP is overly broad, which may result in greater use of broad-spectrum antibiotics.

The prevailing notion is that many patients in the community will be at the lowest risk for experiencing MDR pneumonia and can be treated with a less broad anti-infective regimen. Patients with increasing exposure to the healthcare system will receive initial anti-infective therapy that is more broad in an effort to target MDROs. The investigator group believes that it is not simply exposure to the healthcare system that predicts the incidence of MDR pneumonia (i.e., criteria for HCAP), but rather, the "intensity" of exposure to the healthcare system that is predictive of MDR pneumonia. The aim of this study is to identify risk factors for MDR HCAP pneumonia in critically ill patients. .

Inclusion Criteria:

• Age ≥ 18 years old
• ICU admission
• Empiric or directed anti-infective treatment for pneumonia for ≥ 5 days

Exclusion Criteria:

• Patient stay in ICU for < 24 hours
• Patient transfer to the ICU from a hospital floor following prescription for anti-infective therapy in the previous 24 hours of ICU admission
• Diagnosis of cystic fibrosis or bronchiectasis
• Fungal pneumonia

Patients admitted to an intensive care unit requiring anti-infective therapy for the traetment of pneumonia.