Laboratory confirmed bloodstream infection aetiology in an intensive care unit: eight years study

To evaluate laboratory confirmed bloodstream infection (LC-BSI) aetiology we carried out a prospective study in the general 13 bed ICU of the teaching hospital Policlinico Umberto I in Rome. According to CDC case definitions for LC-BSI, all patients admitted >48h between 2000-2007 to ICU were included. Risk factors (i.e. age, sex, SAPS II), invasive procedures (i.e. endotracheal intubation, vascular and urinary catheterisation), microbiological isolates and their antibiotic susceptibility were screened. Overall 1741 patients (64.8% males, 35.2% females) were included, mean age was 58.1 +/- 19.8, SAPS II score 45.1 +/- 17 and ICU stay 14.0 +/- 21.1 days. Finally, 167 (9.6%) patients developed 203 (11.7%) ICU-acquired LC-BSI and sources of infection were CVC (39.8%), unknown (39.3%), respiratory tract (12.4%), surgical wound (6.5%) and urinary tract (2.0%). Between 2000 and 2007 the incidence of LC-BSI/1000 patient days (14.8 per thousands vs. 7.8 per thousands: p<0.05) and LC-BSI/1000 CVC days (20.7 per thousands vs. 11.4 per thousands; p<0.05) decreased. The onset of infection followed ICU admission by 19.5 +/- 17.7 (mean) and 13 days (median). Crude mortality was 34.8%, and mortality associated with LC-BSI showed a RR 1.61; 95%CI 1.37 - 1.89; p<0.01. The most common pathogens were coagulase negative staphylococci (CNS) (26.2%), methicillin-resistant Staphylococcus aureus (MRSA) (14.9%), Pseudomonas aeruginosa (13.5%), enterococci (9.3%) and Acinetobacter bawnumannii (7.5%). Onset time (days) between ICU admission and LC-BSI was higher (p<0.01) among Gram-negative (22.9 +/- 18.4) compared to Gram-positive (16.6 +/- 15.9), fungi (23.8 +/- 25.3). High early death (<7 days after BSI diagnosis) was associated to A. baumannii (37.5%), Candida spp. (30.0%) and S. aureus (29.7%). Staphylococci presented a very high methicillin resistance (>85%). P. aeruginosa and A. baumannii showed respectively 25% and 68.7% multidrug-resistance. Over 1/3 of Eneterobacteriaceae isolates were extended spectrum beta-lactamase (ESBL), but non resulted resistant to carbapenems. Surveillance showed a high incidence of LC-BSI associated to invasive procedures and the presence of multiresistant bacteria.