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The Spiral method

The Spiral method enables the automatic and standardized plating of a sample. This technique enables to make 4 dilutions on one Petri dish.

The volume of a sample is plated in a form of a decreasing Archimedes spiral (from the center to the periphery). The volume is calibrated and known at every point of the Petri dish.

Why choose the Spiral method?
With the Spiral® method, increase the lab capacities: without intermediary dilutions, make a standardized plating.

- 100 to 1 x 107 CFU/mL on one Petri dish
- Up to 75% savings on consummables
- 1 plating in 8 seconds

How count the colonies?
The sample is deposited on the surface of a rotating petri dish by a precise measuring micro-pump, according to a logarithmically decreasing Archimedes spiral from the center of the dish to its periphery.
According to the setting, the plating corresponds to 3 or 4 dilutions compared to the traditional method. The volume is calibrated and known at every point of the Petri dish.
After incubation, the colonies appear as a spiral trace on the dish.

For a manual counting, count the colonies in the first A or B outer segment and reach a minimum of 20 colonies. Repeat the same operation on the opposite side of the Petri dish.
The number of the minimum value (15 or 20) can depend on the criteria of the researched parameter.
n : Bacterial concentration en CFU/mL
N : Number of counted colonies
D : Dilution factor of the sample
V : Deposited volume in the counted sector in μL (Cf. Volumes Constants)


Examples of plated dishes with easySpiral® and easySpiral® Pro
Bacillus Cereus on PCA

Bacillus Subtilis on PCA
Escherichia Coli on MacConkey
Lactobacillus casei on MRS
Pseudomonas Aeruginosa

The Spiral method, 25 years of experience
In 1973, Dr Ed. Campbell, researcher at the FDA (Food & Drug Administration), designs the Spiral® method to automate the routine work of bacterial enumeration. He the collaborates with François Jalenques, founder of INTERSCIENCE, and in 1992 patented an updated method in 1992.

Since then the automatic Spiral® platers have been a reference for applications in food microbiology, medical bacteriology, research on food preservatives or cosmetological factors in compliance with the XP V08-034, ISO 7218, ISO 4833-2, ISO 15189, FDA-BAM and AOAC standards.

INTERSCIENCE has proudly launched the easySpiral® and easySpiral Pro®, Spiral® platers which have become references since then in labs worldwide.

The Spiral method, by INTERSCIENCE: discover the easySpiral® range:
easySpiral Pro
easySpiral Dilute

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