Epidemiology of infection in ICUs

Patients admitted to ICUs are at the greatest risk of acquiring nosocomial infections, partly because of their serious underlying disease, but also by exposure to life-saving invasive procedures. Nosocomial infections increase patient morbidity, increase the length of hospital stay and hospital costs, and may increase mortality rates. When serious infections are suspected, treatment must be commenced immediately to increase the likelihood of a satisfactory outcome for the patient. Empirical knowledge, to select appropriate antibiotics, must be used so that the most likely infecting organisms are treated. In the past this has meant that antibiotics with activity against Gram-negative pathogens were most likely to be selected. However, infections where Gram-positive pathogens are responsible (e.g. Staphylococcus aureus, Staphylococcus epidermidis and enterococci) are increasingly being found. The European Prevalence of Infection in Intensive Care Study (EPIC), the largest point-prevalence study of infection in ICUs in Western Europe was carried out on 28 April 1992. Data on 10,038 patients in 1417 adult ICU departments from 17 countries was collected and analysed. Of the ICU patients surveyed, 21% had at least one infection acquired in an ICU. The most common infections acquired in an ICU were pneumonia (47%), other infections of the lower respiratory tract (18%), infections of the urinary tract (18%) and infections of the blood-stream (12%). The bacterial isolates were equally divided between Gram-negative and Gram-positive species. The commonly reported bacteria were Enterobacteriaceae (34%), S. aureus (30%), Pseudomonas aeruginosa (29%), coagulase-negative staphylococci (19%) and enterococci (12%).