- Starting concentration
- Fixed dilution added
- Final target dilution
Getting accurate results when testing organisms for antimicrobial susceptibility requires an understanding of how many microbial cells are in the sample being tested. For example, a highly dense concentration of microbial cells in a sample may lead to abnormal competition for nutrients and may affect their growth rates. This reduced rate of growth could be mistaken as a susceptible response to a particular antimicrobial. Today, microbiology labs must manually prepare specific concentrations of microbial cells prior to testing using imprecise methods such as turbidity – or a measure of the cloudiness of a fluid.
Accelerate developed Dynamic Dilution, a technology to address both problems of manual hands-on time and lack of precision, by allowing for a dynamic range of concentrations to be diluted to a target range – automatically. No manual McFarland preparation is required.
The dilution technology works by first quantifying the unknown starting concentration. Fixed dilutions are added and a second count of microbial cells is performed. Using the resulting cell counts, the final target dilution factor for testing can be interpolated. As a method of control, the performance of dynamic dilution is validated during each run by quantifying the density of microbial cells in the growth control flowcell during antimicrobial susceptibility testing.
The Accelerate Pheno™ system uses automated dynamic dilution to consistently produce the necessary starting concentrations for antimicrobial susceptibility testing, reducing variability and turnaround time.