Overview of Nosocomial Infections Caused by Gram-Negative Bacilli

We analyzed data from the National Nosocomial Infections Surveillance (NNIS) System from 1986-2003 to determine the epidemiology of gram-negative bacilli in intensive care units (ICUs) for the most frequent types of hospital-acquired infection: pneumonia, surgical site infection (SSI), urinary tract infection (UTI), and bloodstream infection (BSI). We analyzed >410,000 bacterial isolates associated with hospital-acquired infections in ICUs during 1986-2003. In 2003, gram-negative bacilli were associated with 23.8% of BSIs, 65.2% of pneumonia episodes, 33.8% of SSIs, and 71.1% of UTIs. The percentage of BSIs associated with gram-negative bacilli decreased from 33.2% in 1986 to 23.8% in 2003. The percentage of SSIs associated with gram-negative bacilli decreased from 56.5% in 1986 to 33.8% in 2003. The percentages pneumonia episodes and UTIs associated with gram-negative bacilli remained constant during the study period. The proportion of ICU pneumonia episodes associated with Acinetobacter species increased from 4% in 1986 to 7.0% in 2003 (P<.001, by the Cochran-Armitage chi2 test for trend). Significant increases in resistance rates were uniformly seen for selected antimicrobial-pathogen combinations. Gram-negative bacilli are commonly associated with hospital-acquired infections in ICUs. The proportion of Acinetobacter species associated with ICU pneumonia increased from 4% in 1986 to 7.0% in 2003.