Nosocomial infections in Swiss university hospitals: a multi-centre survey and review of the published experience. Swiss-Noso Network.

A one-week period-prevalence survey, aimed at assessing the scale of nosocomial infections, was conducted in May 1996 in medical, surgical, and intensive care wards of 4 Swiss university hospitals. Standard definitions by the Centres for Disease Control and Prevention were used except that asymptomatic bacteriuria was not classified as a nosocomial infection. A total of 176 nosocomial infections were found among 156 of the 1349 surveyed patients (prevalence 11.6%; interhospital range 9.8-13.5%). Surgical site infections were most prevalent (30% of all nosocomial infections), followed by urinary tract (22%), lower respiratory tract (15%), and bloodstream infections (13%). The most frequently isolated microorganisms were Enterobacteriaceae (n = 44; 28%), S. aureus (n = 20; 13%), Pseudomonas spp (n = 17; 11%), and Candida spp (n = 16; 10%). One third of all episodes of nosocomial infections were not microbiologically documented. The overall prevalence of nosocomial infections in surgical patients (n = 562) was 16.2% compared to 8.6% for non-surgical patients (prevalence ratio, 1.9; 95% confidence interval [CI95], 1.4-2.5). In one centre, the in-hospital mortality of patients with nosocomial infections was 9.2% (10/109) compared to 3.9% (25/637) for patients without nosocomial infections (odds ratio, 2.47; CI95, 1.15-5.31). Infection rates were similar to those reported by two Swiss pilot studies from the early 1980s. This study offers a reliable measure of the prevalence of nosocomial infections in selected wards at 4 Swiss university hospitals and confirms the importance of nosocomial infections as a heavy burden on health services at the end of this century.