Molecular epidemiology of nosocomial infections in an intensive care unit: results of a one-year surveillance study

Abstract

Background. Nosocomial infections contribute substantially to increased morbidity, mortality and resource
expenditure in Intensive Care Units (ICUs).
Methods. A one-year prospective surveillance study was performed using epidemiological and
microbiological methods to quantify the frequency of infections and the antimicrobial usage, microbiological
environmental sampling and molecular typing of clinical and environmental isolates.
Results. The frequency of ICU-acquired infections was comparable to other Italian ICUs. Most of these
infections were caused by few epidemic clones of Pseudomonas aeruginosa, methicillin-resistant
Staphylococcus aureus and Acinetobacter baumannii. The survival advantage of these epidemic clones over
the sporadic isolates may be related to the multi-resistant profile of the epidemic clones and to the high
usage of some antibiotics in the ICU. Hand contamination of ICU personnel is a likely factor for dissemination
of epidemic clones within the ICU.
Conclusions. The integrated surveillance approach described in this study is able to clarify the complex
epidemiology of ICU-acquired infections and can provide important cues for prevention and control
activities.