European Committee on Antimicrobial Susceptibility Testing-Recommended Rapid Antimicrobial Susceptibility Testing of , , and From Positive Blood Culture Bottles.

Background: Early diagnosis and treatment are important for a good prognosis of bloodstream infections. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommends rapid antimicrobial susceptibility testing (RAST) based on the disk diffusion methodology for 4, 6, and 8 hours of incubation. We evaluated EUCAST-RAST of , , and from positive blood culture bottles.

Methods: Twenty strains of , , and were tested using EUCAST-RAST. Ten antimicrobial agents against and and four agents against were tested. The diameter of the inhibition zone (mm) was compared with the minimal inhibitory concentration (μg/mL) obtained using the Sensititre AST system (TREK Diagnostic Systems, East Grinstead, UK).

Results: For , the percentage of total categorical agreement (CA) was 69.5% at 4 hours, and 87% at 8 hours. For , the total CA was 89% at 4 hours, and 95.5% at 6 hours. For , the total CA was 100% after 4 hours. Discrepancies were observed mainly for with β-lactam antimicrobial agents, and the numbers of errors decreased over time.

Conclusions: EUCAST-RAST for and met the United States Food and Drug Administration criteria at 6 and 4 hours, respectively, whereas that for did not meet the criteria for up to 8 hours. RAST can shorten the turn-around testing time by more than one day; therefore, if applied accurately according to laboratory conditions, antimicrobial agent results can be reported faster.