Anaerobic Storage of Water Testing Plates for the Enumeration of Clostridium spp. to Meet New UK Guidelines

In the new UK methods for the isolation and enumeration of sulphite-reducing clostridia by membrane filtration (The Microbiology of Drinking Water (2004) - Part 6 - Methods for the isolation and enumeration of sulphite-reducing clostridia and Clostridium perfringens by membrane filtration. Methods for the examination of waters and associated materials. Environment Agency) it is recommended that prepared Tryptose Sulphite Cycloserine (TSC) agar plates (such as Thermo Scientific, CM0587 and SR0088E or PO0520A) are stored in a refrigerator (2-8°C) under anaerobic conditions for up to one week prior to use.

The recommendations state that the performance of TSC medium deteriorates during storage due to exposure to oxygen. This can be reversed by pre-reducing the medium prior to use, by storing the plates under anaerobic conditions, for up to a week. Therefore, anaerobic and refrigerated storage is important to maintain the quality and reliability of results.

Thermo Scientific AnaeroGen - for the rapid, convenient and safe generation of anaerobic conditions - is ideal for both the storage and incubation of TSC agar plates. On exposure to air, the AnaeroGen sachet begins to work instantly and, when placed inside the anaerobic jar, produces anaerobiosis swiftly and efficiently (with the recommended 9-13% carbon dioxide), without the need for a catalyst or activating solution and without the evolution of hydrogen.

The plates are simply placed inside an anaerobic jar, such as Thermo Scientific AnaeroJar, with the AnaeroGen sachet and an anaerobic indicator to confirm the absence of oxygen. The lightweight design of Thermo Scientific AnaeroJar makes it ideal for refrigerator storage and movement around the laboratory.

Once the plates have been inoculated it is recommended that they are incubated under anaerobic conditions for up to 24 hours. Thermo Scientific AnaeroGen and AnaeroJar are designed for such anaerobic incubation, providing the ideal environment for the growth of anaerobes such as Clostridium spp.