Epidemiology of nosocomial infections in intensive care units in Rome (Italy): a multicentric prospective study

Objective: This study investigated BSI incidence in the Intensive Care Unit and their impact on the mortality rate compared with others causes. As primary point it has been evaluated the rate of bacteremia per year, the causative organisms, the outcome of infection, the antimicrobial susceptibility patterns, the risk factors and the prevalence of multi-drug resistant Gram-positive and Gram-negative bacilli. As secondary end point, the study evaluated the most significant predictors of mortality among the usual risk factors for acquiring BSI at the admission in the ICU. Methods and materials: The study included 1,318 patients admitted to ICUs. Demographics characteristics, SAPS II score, comorbidities and BSI isolates data were collected. Crude mortality rate compared with the overall mortality rate for all causes were evaluated. Results: 324 BSIs from 1,318 patients were evaluated with a total of 407 isolates: 48.6% were Gram + , 43.7% Gram – (GNB) and 7.6% Candida spp. Among Gram+, 69.1% were Coagulase negative Staphylococci (CoNS), 21.7% Enterococci, 6% S. aureus. Among GNB, 30.8% were K. pneumoniae, 28.8% A. baumannii, 17.4% P. aeruginosa, and 6.7% E. coli. At least one episode of BSI was developed in 175 patients (132/1000 pts/year): 139/175 pts had a monomicrobial BSI and 36/175 had polymicrobial BSI. The overall mortality rate was 25.4%: 82/175 pts with BSI died, (44.4% of pts with monomicrobial BSI vs. 61.1 % of pts with polymicrobial BSI). At univariate analysis, SAPS II score (p = 0.039, OR 1.03, 1.001-1.06 CI), cardiac illness (p = 0.015, OR 2.5, 1.20-5.42 CI), and K.pneumoniae BSI (p= 0.005, OR 2.96, 1.37-6.37 CI) were significantly associated to higher risk of death. A slightly significant association between a polymicrobial bacteremia and a higher risk of death was also found (p= 0.057, OR 2.07, 0.98-4.38 CI). At multivariate analysis, having a K. pneumoniae BSI and cardiac illness at the admission in ICU were confirmed to be significantly associated with higher mortality rate (p= 0.0162 and p= 0.0158 respectively). After stratification for outcome (survivors vs. nonsurvivors), univariate and multivariate analysis were performed. Conclusions: These data suggest that K. pneumoniae BSI , cardiovascular comorbidity and polymicrobial BSI in ICU pts are associated to a higher risk of death.