Bloodstream infections in critically ill patients: an expert statement

Abstract

Bloodstream infection (BSI) is defined by positive blood cultures in a patient with systemic signs of infection and may be either secondary to a documented source or primary-that is, without identified origin. Community-acquired BSIs in immunocompetent adults usually involve drug-susceptible bacteria, while healthcare-associated BSIs are frequently due to multidrug-resistant (MDR) strains. Early adequate antimicrobial therapy is a key to improve patient outcomes, especially in those with criteria for sepsis or septic shock, and should be based on guidelines and direct examination of available samples. Local epidemiology, suspected source, immune status, previous antimicrobial exposure, and documented colonization with MDR bacteria must be considered for the choice of first-line antimicrobials in healthcare-associated and hospital-acquired BSIs. Early genotypic or phenotypic tests are now available for bacterial identification and early detection of resistance mechanisms and may help, though their clinical impact warrants further investigations. Initial antimicrobial dosing should take into account the pharmacokinetic alterations commonly observed in ICU patients, with a loading dose in case of sepsis or septic shock. Initial antimicrobial combination attempting to increase the antimicrobial spectrum should be discussed when MDR bacteria are suspected and/or in the most severely ill patients. Source identification and control should be performed as soon as the hemodynamic status is stabilized. De-escalation from a broad-spectrum to a narrow-spectrum antimicrobial may reduce antibiotic selection pressure without negative impact on mortality. The duration of therapy is usually 5-8 days though longer durations may be discussed depending on the underlying illness and the source of infection. This narrative review covers the epidemiology, diagnostic workflow and therapeutic aspects of BSI in ICU patients and proposed up-to-date expert statements.

Keywords: Antibiotic; Antibiotic stewardship; Bloodstream infections; Critically ill; Duration of therapy; Epidemiology; Multidrug-resistant pathogens; Rapid diagnosis; Sepsis; Source control.

Fig. 1

Bloodstream infections in critically ill patients: main sources and leading pathogens. BSI bloodstream infection, CAP community-acquired pneumonia, HCAP healthcare-associated pneumonia, UTI urinary tract infection, ESBL-PE extended-spectrum beta-lactamase-producing Enterobacterales, SSTI skin and soft-tissue infection, HAP hospital-acquired pneumonia, VAP ventilator-associated pneumonia. Community-acquired BSI: BSI first identified [blood cultures sampling] less than 48 h following hospital admission in a patient without recent exposure to the healthcare system. Healthcare-associated BSI: community-onset BSI in patients requiring chronic haemodialysis, living in a nursing home, or recently exposed to antibiotics, in-home nursing care, or the hospital environment. Hospital-acquired BSI: BSI first identified more than 48 h after hospital admission. ICU-acquired BSI: BSI first identified more than 48 h after ICU admission. Primary BSI indicates BSI without identification of a definite source

Fig. 2

Current workflow of microbiological diagnosis in bloodstream infection. PCR polymerase chain reaction, CfDNA cell-free DNA, AST antibiotic susceptibility testing, BC blood culture. Biochemical tests such as C-reactive protein of Procalcitonin is most of time elevated in case of BSI but not sufficiently accurate to discard the diagnosis. A significant decrease of these biomarkers should be used to shorten the duration of antimicrobial therapy