Bloodstream infection is a major cause of morbidity and mortality despite the availability of potent antimicrobial therapy and advances in supportive care. Bacteremia due to gram-negative bacilli is a significant problem in both hospitalized and community-dwelling patients. These organisms pose serious therapeutic problems because of the increasing incidence of multidrug resistance . Gram-negative bacillary sepsis with shock has a mortality rate of 12 to 38 percent; mortality varies depending, in part, on whether the patient receives timely and appropriate antibiotic therapy [2-4].
The epidemiology, microbiology, clinical manifestations, and treatment of gram-negative bacillary bacteremia will be reviewed here. The epidemiology, clinical manifestations, and treatment of infections due to specific gram-negative bacilli are discussed separately in the appropriate topic reviews.
Gram-negative bacteremia is a frequent cause of severe sepsis and septic shock, which often must be managed prior to the receipt of microbiological data. Antibiotic treatment in the setting of severe sepsis and septic shock in general is discussed in detail elsewhere. (See "Evaluation and management of severe sepsis and septic shock in adults", section on 'Eradication of infection'.)
Prevalence — Gram-negative bacilli are the cause of approximately a quarter to a half of all bloodstream infections, depending on geographic region, whether the onset of the infection is in the hospital or community, and other patient risk factors.
Hospital-onset infections — Gram-negative bacilli were once the predominant organisms associated with hospital-onset bloodstream infections in the United States . Since the 1980s, gram-positive aerobes (eg, coagulase-negative staphylococci, Staphylococcus aureus, and enterococci), and Candida species have increased in relative importance. This change was especially evident in the intensive care unit (ICU) population and thought to be largely driven by device-related infections. In the United States, the National Nosocomial Infections Surveillance (NNIS) System reported that from 1986 to 2003 the proportion of bloodstream infections in ICU patients caused by gram-negative pathogens remained stable at approximately 25 to 30 percent . Similarly, subsequent data from the United States National Healthcare Safety Network demonstrated that approximately a quarter of reported central line-associated bloodstream infections from 2009 to 2010 were caused by gram-negative bacilli .