Ortho-Clinical Diagnostics (OCD) has validated and implemented Millipore's Milliflex Rapid microbiology detection and enumeration system to automate traditional microbiology test methods.
The Milliflex Rapid system is an adenosine triphosphate (ATP) bioluminescence-based system that detects and counts viable microorganisms on a membrane filter.
The system consists of a detection tower, image intensifier controller, image processor, computer, and Milliflex Rapid image analysis software.
It also includes membranes, an ATP bioluminescence reagent kit, and an automatic spray (Autospray) station.
Once users filter their sample, prepare the membrane, and place it onto the tower, they initiate the microorganism detection process through a dedicated computer using software designed specifically for this purpose.
The results display on the computer screen as familiar colony forming units on a membrane filter.
Users can directly compare the results to historical data obtained using traditional membrane or pour plate methods.
The Milliflex Rapid system provides results in less time and with the same reliable results as standard techniques, such as the membrane filtration (MF) method.
The system can test raw materials including water, in-process samples, environmental testing products, and final products.
ATP is found only in living cells and is a direct indicator of cell viability, which enables the technology to provide a direct correlation with currently employed test methods.
ATP is also a universal energy molecule stored in all microorganisms, so the technology is suitable for testing a wide range of sample matrices.
The bioluminescence reaction is catalysed by the addition of the enzyme luciferase, isolated from the firefly.
ATP bioluminescence associated with fluorescence microscopy has been also used in the food industry to detect contaminants in beverages.
The reaction involves ATP, luciferin, luciferase, magnesium and oxygen.
Chemically, ATP transfers its energy to the luciferin and forms luciferyl adenylate.
The luciferyl adenylate is then oxidised by the luciferase in the presence of magnesium ions to form oxyluciferin, carbon dioxide, adenosine monophosphate and pyrophosphates, and the reaction emits light with a quantum yield of about 90 per cent.
The average ATP content of a bacterial cell is around 10-18 moles, and the amount required for measurement is about 200 attomoles.
This is equivalent to one yeast or mould cell or approximately 100 bacterial cells, depending on their metabolic state.
The sensitivity of the reagents, combined with a charge-coupled device (CCD) camera and image processor, requires only a short incubation period to generate enough ATP for detection and enumeration.
Advanced image analysis software captures the light emitted from the microorganisms on the membrane and displays an image of the membrane on a computer screen.
It also displays a count of the number of colonies (or cells) enumerated.
