EUCAST rapid antimicrobial susceptibility testing (RAST) in blood cultures: validation in 55 European laboratories
Authors: Åkerlund Anna , Jonasson Emma , Matuschek Erika , Serrander Lena , Sundqvist Martin , Kahlmeter Gunnar ,   the RAST Study Group, Dzajic Esad , Hansen Dennis Schrøder , Agergaard harlotte Nielsen , Pätäri-Sampo Anu , Manninen Raija , Grönroos Juha O , Rasigade Jean-Philippe , Salka Waël , Boyer Pierre H , Lebessi Evangelia , Zapaniotis Nikolaos , Petinaki Efi , Spiliopoulou Iris , Kolonitsiou Fevronia , Helgason Kristjan Orri , Brazil Jean , Riccobono Eleonora , Lo Cascio Giuliana , Maccacaro Laura , Kolstad Helge , Haukeland Torunn Sneide , Kellokumpu Pirkko-Liisa , Fossum Mjøen Andreas , Tofteland Ståle , Harbak Berit , Hartzen Susanne Hartvig , Haug Hänsgen Siri , Gammelsrud Karianne Wiger , Skolbekken Unni , Michalsen Nina , Brekken Anita Løvås , Pedersen Bodil , Guennigsman Brian , Lia Astrid , Berg Ann Kristin , Marco Francesco , Pitart Cristina , Egea Pilar , Cortes-Cuevas Jose Luis , Machuca Jesus , Wietzke Martin , Dammström Magdalena , Granström Roger , Corneliusson Maria , Skarstedt Marita , Frykfeldt Karin , Ivarsson Carina Lindqvist , Sergejev Adam , Hagström Susanna , Lidén Ulrika , Rydberg Johan , Ramström Hanna , Fröding Inga , Petropoulos Evangelos Alexandros , Ininbergs Karolina , Jalal Shah , Persson Anna-Lena Sundqvist , Kamenska Nina , Granlund Kerstin , Smekal Anna-Karin , Hill Anna , Rådberg Gunilla , Heyman Gabriel , Rodriguez Lized , Vennberg Lisa , Hazırolan Gülşen , Akyar Isin , Gülşen Altınkanat Gelmez , Kaygisiz Ayse Nur Sari , Dzajic Esad , Hansen Dennis Schrøder , Agergaard harlotte Nielsen , Pätäri-Sampo Anu , Manninen Raija , Grönroos Juha O , Rasigade Jean-Philippe , Salka Waël , Boyer Pierre H , Lebessi Evangelia , Zapaniotis Nikolaos , Petinaki Efi , Spiliopoulou Iris , Kolonitsiou Fevronia , Helgason Kristjan Orri , Brazil Jean , Riccobono Eleonora , Lo Cascio Giuliana , Maccacaro Laura , Kolstad Helge , Haukeland Torunn Sneide , Kellokumpu Pirkko-Liisa , Fossum Mjøen Andreas , Tofteland Ståle , Harbak Berit , Hartzen Susanne Hartvig , Haug Hänsgen Siri , Gammelsrud Karianne Wiger , Skolbekken Unni , Michalsen Nina , Brekken Anita Løvås , Pedersen Bodil , Guennigsman Brian , Lia Astrid , Berg Ann Kristin , Marco Francesco , Pitart Cristina , Egea Pilar , Cortes-Cuevas Jose Luis , Machuca Jesus , Wietzke Martin , Dammström Magdalena , Granström Roger , Corneliusson Maria , Skarstedt Marita , Frykfeldt Karin , Ivarsson Carina Lindqvist , Sergejev Adam , Hagström Susanna , Lidén Ulrika , Rydberg Johan , Ramström Hanna , Fröding Inga , Petropoulos Evangelos Alexandros , Ininbergs Karolina , Jalal Shah , Persson Anna-Lena Sundqvist , Kamenska Nina , Granlund Kerstin , Smekal Anna-Karin , Hill Anna , Rådberg Gunilla , Heyman Gabriel , Rodriguez Lized , Vennberg Lisa , Hazırolan Gülşen , Akyar Isin , Gülşen Altınkanat Gelmez , Kaygisiz Ayse Nur Sari 
Published: July 2020

Objectives

When bloodstream infections are caused by resistant bacteria, rapid antimicrobial susceptibility testing (RAST) is important for adjustment of therapy. The EUCAST RAST method, directly from positive blood cultures, was validated in a multi-laboratory study in Europe.

Methods

RAST was performed in 40 laboratories in northern Europe (NE) and 15 in southern Europe (SE) from clinical blood cultures positive for Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus or Streptococcus pneumoniae. Categorical results at 4, 6 and 8 h of incubation were compared with results for EUCAST standard 16–20 h disc diffusion. The method, preliminary breakpoints and the performance of the laboratories were evaluated.

Results

The total number of isolates was 833/318 in NE/SE. The number of zone diameters that could be read (88%, 96% and 99%) and interpreted (70%, 81% and 85%) increased with incubation time (4, 6 and 8 h). The categorical agreement was acceptable, with total error rates in NE/SE of 2.4%/4.9% at 4 h, 1.1%/3.5% at 6 h and 1.1%/3.3% at 8 h. False susceptibility at 4, 6 and 8 h of incubation was below 0.3% and 1.1% in NE and SE, respectively, and the corresponding percentages for false resistance were below 1.9% and 2.8%. After fine-tuning breakpoints, more zones could be interpreted (73%, 89% and 93%), with only marginally affected error rates.

Conclusions

The EUCAST RAST method can be implemented in routine laboratories without major investments. It provides reliable antimicrobial susceptibility testing results for relevant bloodstream infection pathogens after 4–6 h of incubation.