Disc diffusion is one of the simplest and widely used methods for sensitivity testing. Disc testing is an extremely flexible technique, with a wide variety of antibiotics and concentrations available, which can easily be inter-changed as required.

A variety of disc dispensers has always been available from Thermo Scientific, including 6, 8 and 12 place dispensers. Thermo Scientific France has now launched a new square dispenser to complement the range. The new dispenser is designed to accommodate 16 cartridges for use with 120mm square plates which are commonly used in some European countries, including France and Belgium. The robust ergonomic design, light weight and smooth action allow for easy use with one hand. The dispenser ensures the precise positioning of antibiotic discs on the agar surface, and a plunger-lock system indicates if one or more antibiotic disc cartridges are empty, thus preventing contamination of the pins.

Each square dispenser is provided with a box which incorporates a desiccant to help maintain a suitable environment for the antibiotic panel whilst being stored in the fridge. The box has a clear plastic lid to allow for the easy identification of the dispenser in each box.

Dr Libert from the Centre Chirurgical Marie Lannelongue has chosen Thermo Scientific for antimicrobial susceptibility testing: "Approximately 3,000 antibiograms per year are performed in our laboratory. We use six 16 place square dispensers and one 6 place dispenser and we find them extremely easy to use" comments Dr Libert.

To obtain accurate and reproducible results, a key point is the quality of the discs. There are three main international standards for potency of antibiotics in the discs, and manufacturers do not all produce to the same standards:

- FDA specification 67-150% of the stated concentration
- WHO specification 75-135% of the stated concentration
- DIN specification 90-125% of the stated concentration.

Thermo Scientific produce to the DIN specification, the tightest international standard. Moreover, owing to close links with pharmaceutical companies, Thermo Scientific can rapidly introduce new discs into the already comprehensive range.

"We have noticed that Thermo Scientific swiftly introduces new antibiotic agents such as quinupristindalfopristin, for example, and the quality of the discs is very good. This is why we wanted to work with Thermo Scientific" concludes Dr Libert.

For more information on Thermo Scientific’s range of products for antimicrobial susceptibility testing please visit the Thermo Scientific website o contact Carlene Simmons, Thermo Scientific, contact details are at the top of this page.