What Is a RODAC Plate?
RODAC stands for Replicate Organism Detection And Counting. A RODAC plate is a 55 mm contact plate filled with agar that is slightly convex — the medium is filled above the rim of the plate. This convex surface allows direct contact with flat surfaces such as floors, walls, work surfaces, and equipment.
How Does It Work?
The technician simply presses the agar surface directly onto the surface to be tested for 5–10 seconds. Microorganisms present on the surface adhere to the agar. The plate is then incubated and colonies are counted after 24–72 hours depending on the medium type.
When to Use RODAC Plates
RODAC plates are the preferred choice for:
Common Media Types for RODAC
The most frequently used media types in RODAC format include:
RODAC vs. Petri Dish: Key Differences
| Feature | RODAC (55 mm) | Petri Dish (90 mm) |
|---|---|---|
| Fill volume | ~16 ml (convex) | ~20 ml (flat) |
| Primary use | Surface contact | Air settle plates, pour plates |
| Incubation | Standard | Standard |
| Counting | Colony count per cm² | Colony count per plate |
CertaMedia RODAC Plates
CertaMedia supplies RODAC plates in more than 390 media types. All plates are produced under ISO 11133 quality standards with full sterility and performance testing documentation.