Supplements, selective- & growth-

Lyophilised supplements are presented in packs of 10 vials, and for the majority of the supplements each vial is sufficient for 500 ml of medium. Larger and smaller volumes are indicated for relevant products.

The shelf life of freeze-dried supplements is 2-3 years provided they are stored in a refrigerator at 2-8 °C. Once rehydrated the stability of antibiotics varies greatly and will determine the shelf life of the prepared agars and broths. For this reason any unused, rehydrated, supplement should be discarded, as even deep-freezing may not prevent the rapid degradation of the antibiotics. To ensure the correct level of selective supplements the entire vial contents must be added to the stated volume of cooled, molten medium.

Rehydration
Vials should be rehydrated aseptically using a sterile needle and syringe charged with 5 ml of the specified diluent for the particular supplement being added. The supplement should be rehydrated, withdrawn and added to the medium in a single process, followed by immediate disposal of the syringe into an approved container. Under no circumstances attempt to re-sheath an exposed neeldle.

Addition
Most antibiotics are heat labile, and so to prevent a reduction of potency the medium should be cooled to 47 °C by holding in a water bath set at this temperature.

Once the supplement has been added the medium must be gently but thoroughly mixed to ensure that the selective agents are evenly distributed. Failure to do this will result in a range of concentrations in the plates/bottles and consequent inconsistency in results. The shelf life of supplemented media is governed by the stability of the added components, and is generally shorter than unsupplemented agars and broths. For information on the shelf life of prepared media consult the individual product listings in the previous section of the manual.

We can offer you f.e. Egg Yolk (Tellurite) Emulsion, Rabbit Plasma Fibrinogen (RPF), Polymixin B, Novobiocin, and many other supplements.

Please contact us if you need a specific product, we are meeting many customers’ unique requests.