Abstract
Sepsis is the leading cause of death among patients in intensive care units (ICUs) requiring an early diagnosis to introduce efficient therapeutic intervention. Rapid identification (ID) of a causative pathogen is key to guide directed antimicrobial selection and was recently shown to reduce hospitalization length in ICUs. Direct processing of positive blood cultures by MALDI-TOF MS technology is one of the several currently available tools used to generate rapid microbial ID. However, all recently published protocols are still manual and time consuming, requiring dedicated technician availability and specific strategies for batch processing. We present here a new prototype instrument for automated preparation of Vitek®MS slides directly from positive blood culture broth based on an “all-in-one” extraction strip. This bench top instrument was evaluated on 111 and 22 organisms processed using artificially inoculated blood culture bottles in the BacT/ALERT® 3D (SA/SN blood culture bottles) or the BacT/ALERT VirtuoTM system (FA/FN Plus bottles), respectively. Overall, this new preparation station provided reliable and accurate Vitek MS species-level identification of 87% (Gram-negative bacteria = 85%, Gram-positive bacteria = 88%, and yeast = 100%) when used with BacT/ALERT® 3D and of 84% (Gram-negative bacteria = 86%, Gram-positive bacteria = 86%, and yeast = 75%) with Virtuo® instruments, respectively. The prototype was then evaluated in a clinical microbiology laboratory on 102 clinical blood culture bottles and compared to routine laboratory ID procedures. Overall, the correlation of ID on monomicrobial bottles was 83% (Gram-negative bacteria = 89%, Gram-positive bacteria = 79%, and yeast = 78%), demonstrating roughly equivalent performance between manual and automatized extraction methods. This prototype instrument exhibited a high level of performance regardless of bottle type or BacT/ALERT system. Furthermore, blood culture workflow could potentially be improved by converting direct ID of positive blood cultures from a batch-based to real-time and “on-demand” process.
Highlights
Sepsis and septic shock remain associated with high rates of hospital morbidity and mortality (Wisplinghoff et al, 2004) and share the most often a common cause: a bacteremia or bloodstream infection (BSI)
This study describes the development and performance evaluation of an instrument prototype allowing for complete automated processing of positive blood cultures from extraction to target slide spotting to obtain rapid ID of microorganisms with only 2 min of hands-on time
Inoculated Blood Cultures Incubated in BacT/ALERTR 3D System
Summary
Sepsis and septic shock remain associated with high rates of hospital morbidity and mortality (Wisplinghoff et al, 2004) and share the most often a common cause: a bacteremia or bloodstream infection (BSI). Despite the introduction of alternative diagnostic technologies (van Belkum et al, 2012), blood culture remains the “gold standard” for detecting and isolating the causative microorganism (Dubourg and Raoult, 2015). The ID workflow of positive blood cultures requires 18–48 h of additional time for subculture to provide isolated colonies and delays the initiation of targeted antibiotic therapy. Based on a “house-made” protocol including centrifugation and many manual steps, the direct ID by MALDI-TOF MS of positive blood cultures was associated with an 11.3% increase of patients receiving appropriate antibiotic treatment within 24 h of blood culture positivity in comparison to a control group using MALDI-TOF MS ID on subcultures (Vlek et al, 2012)
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