Predisposing factors include Diabetes mellitus Cirrhosis Leukopenia (especially that associated with cancer or treatment with cytotoxic medications) Invasive devices (including endotracheal tubes, vascular or urinary catheters, drainage tubes, and other foreign materials) Prior treatment with antibiotics or corticosteroids Recent hospitalization (especially in an intensive care unit) Common causative sites of infection include the lungs and the urinary, biliary, and gastrointestinal tracts.