Population-based epidemiology and microbiology of community-onset bloodstream infections

Abstract

Bloodstream infection (BSI) is a major cause of infectious disease morbidity and mortality worldwide. While a positive blood culture is mandatory for establishment of the presence of a BSI, there are a number of determinants that must be considered for establishment of this entity. Community-onset BSIs are those that occur in outpatients or are first identified <48 h after admission to hospital, and they may be subclassified further as health care associated, when they occur in patients with significant prior health care exposure, or community associated, in other cases. The most common causes of community-onset BSI include Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. Antimicrobial-resistant organisms, including methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamase/metallo-β-lactamase/carbapenemase-producing Enterobacteriaceae, have emerged as important etiologies of community-onset BSI.

FIG 1

Diagnostic hierarchy from positive blood cultures to community-onset bloodstream infection. BSI, bloodstream infection; HO, hospital onset; HCA, health care associated; CA, community associated. The overall triangular area indicates all positive blood cultures, which may represent contamination (first level), transient bacteremia/fungemia (second level), or “true” BSI (third level). Bloodstream infections are further classified into the three mutually exclusive categories of hospital-associated, health care-associated community-onset, and community-associated community-onset BSIs.