Using contact agar plate for surface monitoring

Surface Monitoring with Contact Plates

Surface monitoring using contact plates method is best for evaluating the effectiveness of hygiene procedures on flat and impervious surfaces.

Viroxy conducts surface monitoring test with contact plates method according to ISO 18593:2018 standard. The method is perfect to acquire samples from flat and impervious surfaces. To comply with the standard and acquire reliable samples, we use Replicate Organisms Detection and Counting (RODAC) plates. These plates are filled with agar for general or specific microorganisms.

The Method

The RODAC plate is gently pressed onto selected surfaces to acquire surface samples. The contact plates to evaluate bacterial presence contains TSA while the contact plates to evaluate the presence of yeast and mould contains SDA.

In instances where a sample is collected right after disinfection, appropriate neutralizer can be added to the agar if disinfectant residue is suspected.

The plate is incubated for the required time. Bacteria require 2 days of incubation at 37°C. Yeast and fungi require at least 3 days of incubation at 30°C. The colonies are then counted to determine the number of organisms on the surface area.

Contact plates are easy to handle and it’s the easiest method of sample collection. However, it is not suitable for uneven surfaces. Contact plate method may also show confluent growth of microbes where the colonies are not discrete enough for easy counting.

Sample Site Selection Criteria 

When selecting sites to be sampled, it is important to ask the following questions:

Include sites that are known to harbor high-levels of microorganism.


Colony Findings

Findings are categorised according to this table.


Service Request Process

  1. To request for this service, submit your enquiry through the contact form and we will contact you. Alternatively, call us at +603 2630 8888 for a discussion.
  2. Please determine the size of the premises you wish to test before discussing with us. 
  3. List potential sites of contamination that may require testing such as door handle, playpen, table etc.
  4. Wait for an e-mail from us which will contain a submission form and quotation. Fill in your details if you agree and send the form back to us.
  5. Wait for a sample acquisition date from us.
  6. Collect contact plates from us and acquire surface samples according to the instructions provided. If you'd prefer us acquiring the samples for you, it is possible but appropriate travel fees will be applied.
  7. Send us the sample plates in ice cold condition within 24 hours.
  8. Wait for the result from us. It takes one week to gather the result and another week to generate test report and issue a certificate.

Call us at +60 (0)3 2630 8888 to see how we can help you