Validation of Rapid Antimicrobial Susceptibility Testing directly from blood cultures using WASPLab®, including Colibrí™ and Radian® in-Line Carousel

Abstract

With the increase in antimicrobial resistance, fast reporting of antimicrobial susceptibility testing (AST) results is becoming increasingly important. EUCAST developed a method for rapid AST (RAST) directly from the broth of positive blood cultures (BC). Inhibition zones are read after 4, 6, and 8 h, with specific breakpoints per time point. We evaluated the RAST method based on EUCAST disk diffusion methodology with inoculation of BC broth using WASPLab® (inclusive Colibrí™ and Radian®). Forty-nine non-duplicate strains were tested: Escherichia coli n = 17, Klebsiella pneumoniae n = 7, Pseudomonas aeruginosa n = 4, Acinetobacter baumannii n = 2, Staphylococcus aureus n = 10, Enterococcus faecalis n = 6, and Enterococcus faecium n = 3. Results were compared to direct AST and standardized AST. Good categorical agreement was obtained at all time points for all groups, except P. aeruginosa. RAST cut-offs for extended-spectrum β-lactamase (ESBL)-producing Enterobacterales enabled the detection of all included ESBL isolates (n = 5) at all time points, except for 1 E. coli ESBL after 4 h. RAST cut-offs for carbapenemase-producing Enterobacterales enabled the detection of only one carbapenemase after 6 h. However, all carbapenemases (n = 3) were correctly detected after 8 h. Two methicillin-resistant S. aureus were included; both were correctly categorized as cefoxitin-resistant at 6 and 8 h. At 4 h, there was insufficient growth for inhibition zone interpretation. EUCAST RAST is a fast supplementary tool for direct AST of positive BC. WASPLab® provides a significant advantage as pictures are made automatically implicating that we are not strictly bound to the time points for inhibition zone interpretation.

Evaluation of the compatibility of EUCAST Direct Rapid Antimicrobial Susceptibility Test (RAST) Method Results with Automated Systems in Positive-Signaling Blood Culture Bottles

“…Error rates in the studies were not concentrated on single antibiotic or speci c bacteria. (Herroelen et al 2022). The largest study on Gram-positive bacteria was done by Jasuca et al (Jasuja et al 2020).…”

Evaluation of Automated Disk Diffusion Antimicrobial Susceptibility Testing Using Radian® In-Line Carousel

“…Identifying the causative bacteria of an infection and performing antimicrobial susceptibility testing (AST) to determine a susceptibility profile are crucial assignments in clinical microbiology laboratories. The AST profile enables good antibiotic prescribing, optimal patient care, and prevention of bacterial resistance by initiating appropriate escalation or de-escalation of antibiotics [1][2][3]. Different AST methods utilize the presence or absence of bacterial growth on a solid agar plate or liquid growth medium containing antibiotics to determine the sensitivity of the bacteria [4,5].…”

“…Designing and implementing laboratory automation systems plays a crucial role in improving productivity, traceability, and quality and is an ongoing process [2,7,10]. One such automation system is WASPLab® (Copan, Brescia, Italy), which enables automated inoculation of specimens, incubation of solid plates, and analysis of bacterial cultures through images [11,12].…”

“…One such automation system is WASPLab® (Copan, Brescia, Italy), which enables automated inoculation of specimens, incubation of solid plates, and analysis of bacterial cultures through images [11,12]. Additionally, Copan has developed the Radian® in-line Carousel and Radian® expert System to complement WASPLab® by automating antimicrobial disk diffusion testing and interpretation [2,3]. It contains a carousel that is capable of holding up to 50 antimicrobial discs.…”