Surface Monitoring

Monitoring the microbial flora of environmental surfaces, manufacturing plants, and equipment is an important stage in achieving Good Manufacturing Practices in facilities handling pharmaceuticals, medical devices, food or cosmetics.

Pharmaceutical and medical device manufacturing facilities have stringent sterility requirements for surface sampling in cleanrooms and isolators. Methods to monitor the environmental flora have been described using either contact plates or by swabbing technique. 

The contact plate method is recommended when quantitative data are sought from flat, impervious surfaces.

Disadvantages of the contact plate method are that this method is not suitable for sampling of irregular surfaces, confluent growth of microorganisms can occur, and the media residue must be removed from the sampling site.

Swabbing is employed for equipment and irregular and hard-to-reach places. It can fit easily into equipment recesses, nooks, and crevices, surfaces where contact plates are not suitable. The swab method may also be used on flat surfaces, when a specific the sample size is defined. Types of swabs that may be used for the swabbing technique include cotton, synthetics, and calcium alginatematerials with the appropriate diluent. Disadvantages of the swab method are that sampling and technique (initial dilution) can affect the results and that the method requires manipulation to culture the sample.

Abiolabs can perform identification work on any growth observed on non-selective culture media.

Applied Standard: ISO 14698-1/2


Contact plates are filled so that the media forms a dome. The nutrient medium used in the contactplate may also contain a neutralizing agent. The surface of the media is pressed against the surface being tested. The resulting sampled area for a 50mm plate is approximately 25 cm2. The plates are incubated for the required amount of time, and colonies, if present, are then counted. 

The swab method involves obtaining the sample by rubbing a sterile swab, moistened with anon-nutritive medium in several directions over a standardized sample area. The swab is then placed into a specified amount of rinse solution and agitated to transfer the microorganisms present on the swab into the solution. The collection medium may be tested by a most probable number method, membrane filtration method, or direct plating method.