Implementation of EUCAST short incubation break points directly from blood culture bottles in a private microbiology laboratory

Abstract

Background: Traditional antimicrobial susceptibility results require overnight incubation. A faster turnaround time would allow earlier commencement of targeted therapy and minimise the use of broad spectrum antibiotics. Methods: The Rapid Antimicrobial Susceptibility Testing (RAST) methodology published by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) were applied to a representative sample of positive blood cultures from March to August 2019 and compared to the currently used Vitek 2 system and assessed for major [one method reporting sensitive (S) and the other resistant (R)] and minor errors [one method reporting increased exposure (I) and the other S/R]. Results: Nineteen isolates (12 Escherichia coli, 3 Staphylococcus aureus, 2 Klebsiella pneumoniae and 2 Pseudomonas aeruginosa) were tested. Six hour RAST results exhibited no major or minor errors. All 96 (100%) of the interpretable isolate/antibiotic combinations were concordant. Thirteen (12% of total) combinations fell in the area of technical uncertainty (ATU) and had to be tested using the pre-existing method. Conclusion: The EUCAST RAST methodology was found to be useful at our laboratory for the commonly isolated blood culture pathogens. While ongoing testing of isolates will be required to fully validate this methodology, it holds promise for laboratories using EUCAST guidelines.