Abstract
A key predictor of morbidity and mortality for patients with a bloodstream infection is time to appropriate antimicrobial therapy. Accelerating antimicrobial susceptibility testing from positive blood cultures is therefore key to improving patient outcomes, yet traditional laboratory approaches can require 2–4 days for actionable results. The eQUANT—a novel instrument utilizing electrical biosensors—produces a standardized inoculum equivalent to a 0.5 McFarland directly from positive blood cultures. This proof-of-concept study demonstrates that eQUANT inocula prepared from clinically significant species of Enterobacterales were comparable to 0.5 McF inocula generated from bacterial colonies in both CFU/ml concentration and performance in antimicrobial susceptibility testing, with ≥ 95% essential and categorical agreement for VITEK2 and disk diffusion. The eQUANT, combined with a rapid, direct from positive blood culture identification technique, can allow the clinical laboratory to begin antimicrobial susceptibility testing using a standardized inoculum approximately 2–3 h after a blood culture flags positive. This has the potential to improve clinical practice by accelerating conventional antimicrobial susceptibility testing and the resulting targeted antibiotic therapy.
Highlights
A key predictor of morbidity and mortality for patients with a bloodstream infection is time to appropriate antimicrobial therapy
A 0.5 McF is a measurement of turbidity which results in a bacterial suspension equal to 1–2 × 1 08 colony forming units per mL (CFU/mL) for E. coli ATCC 2 592215
Rapid antimicrobial therapy is critical for patients with a bloodstream infection, and the suitability of the initial empiric antibiotics administered by the clinician must be confirmed by antimicrobial susceptibility testing (AST) results as soon as possible
Summary
A key predictor of morbidity and mortality for patients with a bloodstream infection is time to appropriate antimicrobial therapy. The eQUANT—a novel instrument utilizing electrical biosensors—produces a standardized inoculum equivalent to a 0.5 McFarland directly from positive blood cultures This proof-of-concept study demonstrates that eQUANT inocula prepared from clinically significant species of Enterobacterales were comparable to 0.5 McF inocula generated from bacterial colonies in both CFU/ml concentration and performance in antimicrobial susceptibility testing, with ≥ 95% essential and categorical agreement for VITEK2 and disk diffusion. There have been many efforts over the years to develop methods to generate standardized 0.5 McF suspensions directly from a PBC using serum separator tubes, lysis filtration, centrifugation or simple dilutions[4,16,18,19,20,21,22] While their performance is often high, the methods remain varied, manual and time-consuming and may require complex in house verification. Their appeal is clear, in that they allow a laboratory to use the AST system already in place and still reduce the timeline between a blood culture flagging positive and the initiation of AST
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