FAQs on our prepared media

By Gill Power

We receive numerous questions every day about the Redipor range of prepared media products and SAS active air samplers.  The Redipor range is mainly focused on the needs for environmental monitoring (EM), sterility testing and operator and process validations. The answers to the most frequently asked questions can be found on the FAQ section at the bottom of our product pagesWe cannot publish the answers to every question we are asked but here are the answers we give to other common questions we receive from customers about Redipor, ready-to-use culture media:

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Q:  Which way up should I store my agar plates?

A:  For all types of plates (contact, 55mm, 90mm and 140mm) with the agar at the bottom which you will find is as packed.  This is the most secure orientation for transport and storage of sealed packs.  Redipor plates are conditioned at room temperature before packing.  Our unique process stabilises the moisture content to minimise condensation.

Q:  Is the standard plate packaging impermeable to VHP (Vaporised Hydrogen Peroxide)?

A:  We have not validated the flow wrap for VHP permeability, so the answer is we do not know.  The same can be said for those products where the old-style poly bags with cling film are still used.  We believe the Barrier Packs offer you the best solution when fumigating plate packs in Isolators or RABs as they have been validated.

Q:  Are the raw materials in Redipor prepared media TSE Free?

A:  Our suppliers guarantee the source of any animal-related products are from countries where BSE is either not endemic or completely absent (Australia, New Zealand and the USA).  This means that our microbiological media is TSE free. If you require our TSE Policy statement, it is available here on our resources page.

Q:  Do you sell CE marked media for Clinical Diagnostics?

A:  No.  The focus for Cherwell Laboratories has always been supplying to Pharmaceuticals, Biotech, Hospital Pharmacies and Sterile (Medical Devices) manufacturing. We also supply some prepared, selective media to Toiletries & Cosmetics, Agri-Food & Beverage manufacturers, research, education and environment.  CE marked media formulations have different requirements in terms of Quality Control Testing for pathogens.  

Much of the media used in clinical diagnostics require refrigeration as they contain unstable ingredients such as blood and certain antibiotics.  As the Redipor range of prepared media is all about room temperature storage, we do not make media used in clinical diagnostics.

 Q:  The agar in the plates have cracked by the end of incubation. Is this a problem and if so how can it be fixed?

A:  Settle plates will inevitably lose moisture during exposure and incubation.  The requirement is that sufficient water activity remains at the end of incubation to support microbial growth.  Cracking or splitting of the agar is undesirable because if there is growth on the plate it might spread along the crack and result in difficult or erroneous colony counting.   

If you are exposing plates in an environment with lower relative humidity or more air changes, such as a biological safety cabinets, UDAF or isolators; you might find that a deeper fill plate will perform better. Both Tryptone Soya Agar (TSA) and Sabouraud Dextrose Agar (SDA) irradiated Redipor plates are also available with a 27ml fill volume.

Q:  My daughters have been asked to devise an experiment for Science Week at school. We want to look at bacteria found in the house. Can you advise us, please?

A:  Microbiology in the home can be both interesting and safe provided you take sensible precautions.  You don't say what age your daughters are but you might consider that the risk of handling agar plates when they have grown bacteria, is similar to them handling a piece of rotting food - so you would want to supervise their hygiene and keep everything sealed. You and the school might also want to think about whether you want them to take the resulting plates into school.

If you have a question that we have not covered either here or on our product pages, please don't hesitate to get in touch. We are happy to offer help and advice. Alternatively, download our comprehensive guide The Pharmaceutical and Cleanroom Industry's Pocket Guide to Prepared Culture Media. 





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