Rodac plates

Surface Monitoring Contact (or Rodac) plates of growth media are applied to surfaces such as bench tops, walls, and personnel and then incubated. Colony-forming units (cfu) are counted and identified. 

Cotton swabs or RODAC plate (nutrient agar culture medium)... 

The use of contact plates is the recommended technique. The RODAC plate method is the simplest, but it is useful only for flat surfaces. Swab samples afford examination of corners, crevices, and other area inaccessible to RODAC plates. 

Two days before testing incubate in inverted position a sufficient number of RODAC plates (or contact plates), swabs, agar strips, and plates for fingerprints. 

Environmental control monitoring SOP No. All result of active air sampling settle plates RODAC plates, swabs and operator s gloved hand plates within the acceptance limit... 

There are three basic methods which have been employed for evaluation of microbiological content on surfaces. These include ROD AC (Replicate Organism Detection and Counting) plates, swab testing, and agar overlay or rinse techniques. RODAC plates are the most commonly used of the surface monitoring methods. However, they are not suitable for irregular surfaces, in which case swab techniques are used. 

The contact plate involves pressing an agar plate against the surface being monitored. The Rodac plate (diameter 55 mm) is a commercially available peiri dish designed for use as a contact plate. 

An example of how this works may be useful three separate random samples (obtained by pressing Rodac plates onto the countertop randomly) are taken... 

SoBOLESKY, W.J. 1968. The Rodac plate—a useful tool for sanitarians. /. Environ. Health 30(5) 525-527. 

Disinfection efficacy must be proved with contact plates (RODAC plates, see Sect. 31.6) specifications of the results can be found in Annex 1 of the European GMP. 

Monitoring of flat surfaces is carried out with contact plates of agar medium in a 55 mm dish. The medium has a slightly convex surface which can be gently pressed on the surface to be examined, see Fig. 31.2. These plates are sometimes known as RODAC plates (RODAC is the brand... 

All handlings should be performed in a way as aseptic as possible. Prepare the culture medium according to the USP and fill the medium into sterile RODAC dishes to the brim to obtain a convex surface. Extreme care should be taken to prevent the formation of air bubbles and to prevent the medium from overflowing (if either occurs, these plates should be discarded). Allow the plates to solidify. Preincubate the plates at 55°C for 24 h and then at 25°C for 24 to 48 h. 

Carefully introduce the RODAC dish at the area to be tested and remove the lid. Carefully but firmly press the plate with a slight rolling movement onto the surface being examined and hold for a few seconds without moving it. Remove the dish and replace the lid immediately. The tested area is then to be cleaned and disinfected with 70% alcohol. 

Contact plates are used when sampling regular or flat surfaces. The test is performed with RODAC (replicate organisms detecting and counting) plates, or contact plates, where the convex agar surface rises above the brim of the plate. 

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