EUCAST has developed a method for rapid AST (reading at 4, 6 or 8h and since April 2022 also after 16-20 hours incubation) directly from positive blood culture bottles (RAST). The rationale is available in JAC.
Following the initial development, published in 2019, a clinical trial in 55 laboratories was performed and published in 2020.
The EUCAST RAST method is based on the EUCAST standard disk diffusion methodology, but with modified inoculum, incubation time, modified reading instructions and specific RAST breakpoints.
The purpose of the EUCAST RAST method is to allow rapid susceptibility test results directly from positive blood cultures. The RAST method provides specific breakpoints for readings at 4, 6 and/or 8 hours incubation. In addition, RAST breakpoints for 16-20 hours incubation have been developed. Results should only be read after 16-20 hours when it is not possible to read results after 4, 6 and/or 8 hours incubation, for example due to limited opening hours.
The method has been validated for the following species: Escherichia coli, Klebsiella pneumoniae (including Klebsiella variicola and Klebsiella quasipneumoniae), Salmonella enterica, Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium and Streptococcus pneumoniae.”
The EUCAST Development Laboratory makes baseline data on the relationship between zone diameters, MIC-values and ATUs publicly available.
If you have implemented, or aim to implement, RAST according to the EUCAST method, please send an email stating the name, town and country of your laboratory, and tell us if you were successful or encountered difficulties. Contact EUCAST via the form below.
Looking for more information? Get in touch with an EUCAST representative today!