How to Automatize the Preparation of Microbial Suspensions for Antimicrobial Susceptibility Testing AST

Automated Antimicrobial Susceptibility Systems provide reliable results improving clinical outcomes although the microbial suspension preparation is still completely manual. Colibrí® is a new automated system able to pick colonies from plates, re-suspend them in saline solution, check the turbidity of the suspension with the on-board nephelometer and adjust it if required.
The aim of the study was to compare manual microbial suspensions preparation for Antimicrobial Susceptibility Testing (AST) to Colibrí® automated preparation.
Colibrí® is able to:
– Pick colonies using disposable tips (1)
– Release bacteria colonies in a saline solution tube (2)
– Check the microbial suspension turbidity using the on-board nephelometer (3)
– Adjust the microbial suspension adding colonies or saline to obtain a 0.5 MacFarland
– Prepare the microbial dilution needed for processing with AST system
– Prepare the purity plate from the microbial suspension (4)

The results were interpreted with Biomerieux Expert System EUCAST 2015:

– 318 antibiotic combinations were tested for Gram positive: 1 minor error (0.31%) and 1 major error (0.31%) were found.
– 306 antibiotic combinations were tested for Gram negative: 9 minor error (2.94%) and 1 very major error (0.32%) were found.
– Only 1 discrepant result could be related to the viable count where the manual preparation was 5-fold higher than Colibrí ® microbial preparation.
Five out of the 44 strains tested were defined as MDR organisms
according to Magiorakos et al 2011 (1).

The data generated in this study demonstrate Copan Colibrí®:
– is able to automatically prepare microbial suspensions from different bacteria colonies directly from agar plate culture.
– provides comparable results to those obtained with manual preparation
– standardizes the preparation of microbial suspensions for AST and purity plates eliminating the person to person variability.
– Reduce the exposure to pathogens improving staff safety

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Colibrí™ Universal Colony Picker