title: Are most ICU infections really nosocomial? A prospective observational cohort study in mechanically ventilated patients.
abstract: A prospective cohort study was undertaken with two end points: (i) to compare the 48 h time cut-off with the carrier state criterion for classifying infections, and (ii) to determine a time cut-off more in line with the carrier state concept. All patients admitted to the intensive care unit and expected to require mechanical ventilation for a period > or = 3 days were enrolled. Surveillance cultures of throat and rectum were obtained on admission and thereafter twice weekly to distinguish micro-organisms that were imported into the intensive care unit from those acquired during the stay in the unit. A total of 117 patients with median age of 61 years and median Simplified Acute Physiology Score II of 42, were included in the study. Of these patients, 48 (41%) developed a total of 74 infection episodes. Using the 48 h cut-off point, 80% of all infections were classified as ICU-acquired. According to the carrier state criterion, 44 infections (60%) were of primary endogenous development caused by micro-organisms imported into the intensive care unit. Seventeen secondary endogenous (23%) and 13 exogenous (17%) infections were caused by bacteria acquired in the unit. The carrier state classification allowed the transfer of 49% of infections from the ICU-acquired group into the import group. A time cut-off of nine days was found to identify ICU-acquired infections better than two days. These data suggest that monitoring of carriage of micro-organisms may be a more realistic approach to classify infections developing in the intensive care unit.
authors.affiliation: Department of Anaesthesia and Intensive Care, University of Trieste, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Silvestri
authors.forename: C
authors.initials: C
authors.lastname: Monti Bragadin
authors.forename: M
authors.initials: M
authors.lastname: Milanese
authors.forename: D
authors.initials: D
authors.lastname: Gregori
authors.forename: C
authors.initials: C
authors.lastname: Consales
authors.forename: A
authors.initials: A
authors.lastname: Gullo
authors.forename: H K
authors.initials: HK
authors.lastname: van Saene
mesh_terms: D000328:Adult; D000368:Aged; D002353:Carrier State / Q000453:epidemiology*; D015331:Cohort Studies; D017714:Community-Acquired Infections / Q000453:epidemiology; D003428:Cross Infection / Q000453:epidemiology* / Q000209:etiology / Q000517:prevention & control; D005260:Female; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D007558:Italy / Q000453:epidemiology; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012372:ROC Curve; D012121:Respiration, Artificial / Q000009:adverse effects*