Relationship between nasal colonization and ventilator-associated pneumonia and the role of the environment in transmission of Staphylococcus aureus in intensive care units

Abstract

This study assessed the relationship between nasal colonization and ventilator-associated pneumonia (VAP) by Staphylococcus aureus, as well the role of the environment in the transmission of this organism. We performed a cohort study of patients with VAP caused by methicillin-resistant S aureus (MRSA) or methicillin-sensitive S aureus during 2 years in an adult intensive care unit (ICU). All patients had nasal swab specimens obtained at admission and during the ICU stay. Clinical samples also were collected for analysis, as were samples from the hands of health care professionals and the environment, and were typed using pulsed-field gel electrophoresis. S aureus VAP represented 12.5% of the cases, and statistical analysis identified colonization as a risk factor for the development of this infection. MRSA was isolated from the environment and hands, indicating the existence of a secondary reservoir. Molecular typing revealed a polyclonal profile; however, clone J was the most frequent (45.5%) among isolates of MRSA tested, with a greater profile of resistance than the other isolates. There was strong evidence suggesting transmission of MRSA to patients from the environment. Nasal colonization for S aureus is a risk factor for development of VAP.