Sabouraud Dextrose Agar with Chloramphenicol

Technique

Contact plates are used in the microbiological control of disinfection and cleaning of surfaces. They act simultaneously as a sampler and incubation culture medium without the need for any other intermediate steps.

The plates come in a form appropriate for this function and can be used with different culture media depending on the type of microbe that needs to be controlled. On average the plates provide a contact surface of approximately 25 cm².

To use, remove the cover and gently press the culture medium on the surface to be controlled, ensuring contact between the two surfaces. The contact plate is removed and covered with the lid to prevent air contamination. It is advisable that the lid is secured with adhesive tape and the bottom labelled with the sampling data (place, date and time).

If the sample surfaces are rough, the contact plates will not make good contact, even when the pressure is increased. In these cases it is advisable to delineate a sample surface area of 25 cm² and rub this area vigorously with a wet sterile swab and then rub the swab over the contact plate.

If verifying the effectiveness of a cleaning or disinfection process, contact plates should be used within two hours after the end of the process, ensuring that the sample surface is dry. It is advisable to always include positive controls, sampling the area before disinfection or dirty areas beside the disinfected area.

The technician will determine the frequency of sampling and disinfection according to performance criteria. Apply the agar directly onto the surface to be monitored ensuring that the pressure is distributed over the whole plate for 10 seconds. Clean the surface where the sample was collected in order to remove any traces of agar.

The inoculated plates are incubated at 32-35 °C for 24-48 hours and examined daily. For fungi, the incubation is carried out at 22-25 °C for 5 days and examined daily.

Note: Contact plates are used for monitoring the microbiological contamination of surface and air inside cleanrooms, isolators, RABS, food industries and hospitals. The double/triple irradiated wrapping ensures that the package itself doesn't contaminate the environment as the first wrapper is removed just before entering the clean area.

The plates must be kept in their original packaging (blisters) to guarantee their stability until the end of their expiration date.

Physical/chemical control

Microbiological control

Inoculate: practical range 100 ± 20 CFU; min. 50 CFU (productivity) / 10⁴-10⁶ (selectivity).

Analytical methodology according to ISO 11133:2014/Amd 1:2018; A2:2020.

Aerobiosis. Incubation at 22.5 ± 2.5 °C. Reading at 24-72 h for bacteria and 3-5 days for yeasts and moulds.

Microbiological control according to ISO 11133:2014/Amd 1:2018.

Sterility control

Incubation 48 h at 30-35 °C and 48 h at 20-25 °C: NO GROWTH.

Check at 7 days after incubation in same conditions.

• AJELLO, L. (1957) Cultural Methods for Human Pathogenic Fungi. J. Chron. Dis. 5:545-551.
• EUROPEAN PHARMACOPOEIA 6.0 (2008) 6th ed. § 2.6.13. Microbiological examination of non-sterile products: Test for specified microorganisms. EDQM. Council of Europe. Strasbourg.
• GEORGE, L.K., AJELLO, L. & PAPAGEORGE, C. (1954) Use of Cycloheximide in the Selective Isolation of Fungi Pathogenic to Man. J. Lab. Clin. Med, 44 (422-428).
• ISO 11133:2014/Amd 1:2018. Microbiology of food, animal feed and water. Preparation, production, storage and performance testing of culture media.
• PAGANO, J. LEVIN, J.D. & TREJO, W. (1957-58) Diagnostic Medium for Differentiation of Species of Candida. Antibiotics Annual, 137-143.
• SABOURAUD, R. (1910) Les Teignes. Masson, Paris.