Clinical blood samples were collected from patients suspected of having sepsis attending the Infectious Disease ER at the University Hospital of Örebro. In addition to the standard 4 blood culture flasks drawn per patient for routine diagnostics, an extra flask was taken for the present study. Of the approximately 500 clinical samples collected so far 28 identified as positive in normal clinical routine diagnostics were selected and are presented here. Pathogen ID was performed in a prototype ASTrID® system, using a panel of 30 targets including 26 specific pathogens, 3 resistance markers and one pathogen group. Identification directly from patient without waiting for a positive blood culture achieved sensitivity of 97% and specificity of 99.6%, compared to conventional analysis on positive blood cultures.
AST analysis on clinical isolates (E.coli) spiked in blood (inoculum consistent with 10 CFU/ml) was performed in a prototype ASTrID® system, and results compared with broth microdilution according to ISO 20776. The AST results directly from blood were 98.8% in essential agreement with reference broth microdilution and 98.8% in categorical agreement to EUCAST clinical breakpoints.
AST from positive blood cultures - ASTar
The test panel used in this study contained 10 different antimicrobials in 5-11 concentrations per antimicrobial, covering breakpoints set by EUCAST. Two clinical isolates in ten replicates of each species (P. aeruginosa, E. coli, K. pneumoniae, S. aureus, E. faecalis) were spiked into blood culture flasks and incubated until flagged positive. True MIC values were obtained within 6 hours achieving an overall essential agreement (EA) of 96% and a categorical agreement (CA) of 95% compared to reference broth microdilution method in all 476 bacteria-antimicrobial agent combinations tested.