What is Contact Plate Method?
Contact Plate (RODAC - Replicate Organism Direct Agar Contact) Method - Contact plates are special petri plates containing suitable agar media with a raised agar surface above the rim of the plate. For sampling, the plate is inverted and agar is pressed against the sampled surface.
The plate is rolled while applying the pressure and is then incubated after replacing the cover at appropriate temperature and for appropriate time according to the purpose. Margin figure shows the growth on the contact plate. The colonies on each plate are counted. When surfaces to be examined are cleaned with detergents, neutralizers (lecithin, Twin 80 etc.) have to be incorporated in the medium.