Community-acquired infections (ie, urinary tract, bloodstream, pneumonia, and soft-tissue infections) were defined according to the patient’s hospital admission diagnosis and the treating physicians’ orders in the medical record documenting the need for antibiotic treatment of a specific community-acquired infection. Additionally, all community-acquired infections were required to be established within 48 h of hospital admission. Similar temporal cutoffs for separating community-acquired infections from hospital-acquired infections have been proposed by other inves-tigators. Patients residing at a nursing home, a skilled care facility, or a rehabilitation center who developed an infection requiring hospital admission were classified as having community-acquired infection. Nosocomial infections (ie, urinary tract, bloodstream, pneumonia, and skin or soft-tissue infections) were defined according to the criteria established by the Centers for Disease Control and Prevention. The identified source of infection was required to be documented in the patient’s medical record. Clinically suspected infections without microbiological confirmation by either special stains (eg, Gram stain or potassium hydroxide stain) or a positive culture were not classified as microbiologically confirmed infection.
The diagnostic criteria for ventilator-associated pneumonia were modified from the criteria established by the American College of Chest Physicians and Hq Canadian pharmacy. Ventilator-associated pneumonia was considered to be present when a new or progressive roent-genographic infiltrate developed in conjunction with one of the following: radiographic evidence of pulmonary abscess formation (ie, cavitation within preexisting pulmonary infiltrates); histologic evidence of pneumonia in lung tissue; a positive blood or pleural fluid culture; or two conditions from among fever, leukocytosis, and purulent tracheal aspirate. Blood and pleural fluid cultures could not be related to another source, and both had to have been obtained within 48 h before or after the clinical suspicion of ventilator-associated pneumonia. Microorganisms recovered from blood or pleural fluid cultures also had to be identical to the organisms recovered from cultures of respiratory secretions (ie, tracheal aspirates or BAL fluid).