The Spiral Plater is a two-in-one method: diluter and plater at the same time, one of the most time- and waste volume- saving methods of inoculation, that is why more and more microbiological laboratories are using Spiral Plater for bacterial determination.
The Spiral Plating is an official method of the APHA, the AOAC, and recognized by the FDA BAM (Chapter 3). This rapid plating consists of inoculating a known volume of liquid sample on the surface of a rotating agar plate. The volume of the sample that is dispensed, decreases the dispensing syringe moves from the center to the edge of the rotating plate in the Archimedean spiral.
Therefore, the purpose of Spiral Plating is to create serial dilutions in a single plate. The microbial concentration is determined by counting the colonies on a part of the Petri dish where they are easily countable and dividing this count by the appropriate volume.
The Eddy Jet, IUL’s rapid plating
IUL Instruments manufactures the Eddy Jet, a revolutionary approach to rapid plating with a unique system that avoids cross-contamination with its patented micro syringes. IUL’s technology offers a very intuitive user interface without setup times.
The first Eddy Jet was released in 1998 to prevent any cross-contamination from taking place. Years later, IUL manufactured the Eddy Jet 2W that, thanks to its spiral spreader, offers labs the highest sensitivity in the market. Also, Electron Beam micro syringe sterilization makes cleaning cycles unnecessary, saving large amounts of time.
Furthermore, Eddy Jet’s dependable Stepper Microcontroller motors can regulate the instrument’s high precision micros syringe liquid dispensing. Unlike other rapid platings, this approach avoids all the issues relating to cleaning cycles, disinfectant preparation, cross-contamination, unnecessary and complex liquid handling, or stylus calibration, among many others.
Advantages of Eddy Jet
One of the main advantages of Eddy Jet is the amount of time and consumables that can be saved, an example of this would be Petri and solvent plates. Besides this, Eddy Jet patented technology implies that no leftover bleach may affect sample bacteria, avoiding false-negative results.
Eddy Jet can perform more than 25 spiral distributions such as logarithmic, linear, and uniform distribution. Each type corresponds to a different pattern in liquid sample spreading across the spiral and makes suitable a rapid plating even for the most concentrated samples.
How to perform the bacteria count in spiral plating?
After incubation, colonies appear along the line of a spiral and, if they are sufficiently spaced from each other, we can count them on a special grid that associates a calibrated volume with each area. When colonies are counted with the grid, sample volume becomes greater as counting starts at the outside edge of the plate and proceeds toward the center of the plate.
To increase the speed, the count can be performed with an automatic colony counter such as SphereFlash® which has implemented methods to count different types of spreading.
Applications of spiral plating
This rapid plating method is broadly applied for viable microorganism enumeration in milk, cosmetics, and drugs where a single spread can have a detection range between 4.10² and 4.10⁵ in the most useful and better sowing of 50µl.
For more diluted samples with the Eddy Jet can be reached 1.10² to 1.10⁵ using 200µl of the sample, that is not 100% recommended due to the collapse of the spiral lines if the agar is not dry enough.
This method has also been applied to test environmental water samples. Agricultural and environmental industries implement spiral platers in bio-pesticide challenges, frost prevention, and leaf studies. It also can be used for purposes such as spiral MIC tests or mutagenicity assays among others.