Evaluation and validation of Biolog OmniLog (cid:1) system for antibacterial activity assays

Significance and Impact of the Study: The determination of minimal inhibitory concentration of drugs and screening of novel antimicrobial compounds are common practices in clinical and research settings. In this work, the OmniLog (cid:1) system, developed for the identification and metabolic fingerprinting of micro-organisms, was evaluated and validated for antibacterial assay performance. For the three antibiotics tested, OmniLog showed similar results when compared, in parallel, to the standard methodology defined by the Clinical Laboratory Standards Institute. OmniLog offers an option of a flexible, walk-away and label-free system, ideal for increasing the throughput of screening compound libraries for potential antimicrobial activity. Abstract Minimal inhibitory concentration of antimicrobials, determined by the broth microdilution method, requires visual assessment or absorbance measurement using a spectrophotometer. Both procedures are usually performed manually, requiring the presence of an operator to assess the plates at specific time point. To increase the throughput of antimicrobial susceptibility testing, and concurrently convert into an automatic assay, the Biolog OmniLog (cid:1) system was validated for a new, label-free application using standard 96-well microplates. OmniLog was evaluated for its signal strength to ensure that the signal intensity, detected and measured by the system’s camera, was satisfactory. Variability due to the plate location inside the OmniLog incubator, as well as variation between wells, was investigated. Then the system was validated by determining the minimal inhibitory concentration of ciprofloxacin, piperacillin and linezolid against a selected Gram-negative and Gram-positive strains. No significant difference was observed in relation to position of the plates within the system. Plate edge effects were noticeable, thus the edge wells were not included in further experiments. Minimal inhibitory concentration results were comparable to those obtained by conventional protocol as well as to values defined by the Clinical Laboratory Standards Institute or published in the literature.

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