Healthcare-associated bloodstream infection: A distinct entity? Insights from a large U.S. database.

OBJECTIVE: To gain a better understanding of the epidemiology, microbiology, and outcomes of early-onset, culture-positive, community-acquired, healthcare-associated, and hospital-acquired bloodstream infections.

DESIGN: We analyzed a large U.S. database (Cardinal Health, MediQual, formerly MedisGroups) to identify patients with bacterial or fungal bloodstream isolates from 2002 to 2003.

SETTING: The data set included administrative and clinical variables (physiologic, laboratory, culture, and other clinical) from 59 hospitals. Bloodstream infections were identified in those hospitals collecting clinical and culture data for at least the first 5 days of admission.

PATIENTS: Patients with bloodstream infection within 2 days of admission were classified as having community-acquired bloodstream infection. Those with a prior hospitalization within 30 days, transfer from another facility, ongoing chemotherapy, or long-term hemodialysis were classified as having healthcare-associated bloodstream infection. Bloodstream infections that developed after day 2 of admission were classified as hospital-acquired bloodstream infection. A total of 6,697 patients were identified as having bloodstream infection.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN RESULTS: Healthcare-associated bloodstream infection accounted for more than half (55.3%) of all bloodstream infections. Nearly two thirds (62.3%) of hospitalized patients with bloodstream infection suffered from either hospital-acquired bloodstream infection or healthcare-associated bloodstream infection and had higher morbidity and mortality rates than those with community-acquired bloodstream infection. Of all bloodstream infection pathogens, fungal organisms were associated with the highest crude mortality, longest length of stay in hospital, and greatest total charges. Of all bacterial bloodstream infections, methicillin-resistant Staphylococcus aureus was associated with the highest crude mortality rate (22.5%), the longest mean length of stay (11.1 +/- 10.7 days), and the highest median total charges ($36,109). After we controlled for confounding factors, methicillin-resistant S. aureus was associated with the highest independent mortality risk (odds ratio 2.70; confidence interval 2.03-3.58). S. aureus was the most commonly encountered pathogen in all types of early-onset bacteremia.

CONCLUSIONS: Healthcare-associated bloodstream infection constitutes a distinct entity of bloodstream infection with its unique epidemiology, microbiology, and outcomes. Methicillin-resistant Staphylococcus aureus carries the highest relative mortality risk among all pathogens.