Prevalence and risk factors for nosocomial infections in four university hospitals in Switzerland

OBJECTIVE: To determine the prevalence and risk factors for nosocomial infe ctions (NIs) in four Swiss university hospitals. DESIGN AND SETTING: A 1-week period-prevalence survey conducted in May 1996 in medical, surgical, and intensive-care wards of four Swiss university ho spitals (900-1,500 beds). Centers for Disease Control and Prevention defini tions were used, except that asymptomatic bacteriuria was not categorized a s NI. Study variables included patient demographics, primary diagnosis, com orbidities, exposure to medical and surgical risk factors, and use of antim icrobials. Risk factors for NIs were determined using logistic regression w ith adjustment for length of hospital stay, study center, device use, and p atients' comorbidities. RESULTS: 176 NI were recorded in 156 of 1,349 screened patients (11.6%; int erhospital range, 9.8%-13.5%). The most frequent NI was surgical-site infec tion (53; 30%), followed by urinary tract infection (39; 22%), lower respir atory tract infection (27; 15%), and bloodstream infection (23; 13%). Preva lence of NI was higher in critical-care units (25%) than in medical (9%) an d surgical wards (12%). Overall, 65% of NIs were culture-proven; the leadin g pathogens were Enterobacteriaceae (44; 28%), Staphylococcus aureus (20; 1 3%), Pseudomonas aeruginosa (17; 11%), and Candida species (16; 10%). Indep endent risk factors for NI were central Venous catheter (CVC) use (odds rat io [OR], 3.35; 95% confidence interval [GI(95)], 2.91-3.80), admission to i ntensive care (OR 1.75; CI95, 1.30-2,21), emergency admission (OR 1.57; CI9 5, 1.15-2.00), impaired functional status (Karnofsky index 1-4: OR, 2.56; C I95, 1.95-3.17), and McCabe classification of ultimately fatal (OR, 2.50; C I95, 2.04-2.96) or rapidly fatal (OR, 2.25; CI95, 1.52-2.98) underlying con dition: CONCLUSIONS: According to the results of this survey, NIs are frequent in S wiss university hospitals. This investigation confirms the importance of CV Cs as a major risk factor for NI. Patient comorbidities must be taken into account to adjust for case mix in any study comparing interhospital or intr ahospital infection rates.