Thks yr clarification.
I interpret yr query as to the routine necessity (or not) of carrying out "continuous" parallel reference tests for assurance that culture media remain “suitable” for their designated purpose within the context of ISO 17025.
Should say that my recent experience is mainly with factory micro. labs which have less demanding requirements as compared to a commercial service unit. For certification to Food Safety standards, factory micro.labs typically only need to demonstrate a capability “equivalent” to ISO 17025 rather than be officially certified, although some are.
I have done a little net searching concerning micro. lab accreditation via ISO17025. It is quite a complicated subject . Seems the relevance of 17025 to Quality Assurance of micro.lab media is particularly defined via ISO 11133 Pts 1 and 2 respectively.
I did not see any requirement in either 17025 or 11133 (1/2) for maintaining a permanent, continuous parallel activity as (I think) you describe. IMO such a frequent repetition is logistically impractical as a general SOP although I can envisage there might be some particularly sensitive situations where extra care is temporarily justified.
However the particular media characteristics eg type / origin / supply scenarios can influence the methodology / frequency of "validation" of culture media. Details are given in ISO 11133. Some examples / interpretations are shown in acc attachments / PS below which include cases ranging from nil (eg acc2, sec. 3.1[a] ) requirement up to extended test periods (eg PS-SOP).
Here is a commercial document illustrating some operational aspects of the significance of iso 11133 for evaluation of culture media .
Guidelines for Culture Media re ISO 11133.pdf 2.44MB
For comparison, I hv attached 3 example sets of accreditation-related requirements for micro.labs/media below (acc 2-4), as "interpreted" within the context of ISO 17025. Examples of text relating to performance of culture media are at -
acc2 / Sec.3.1
acc3 / sec. 8.3
acc4x / Sec.6.4
I expect the above ideas are similar to yr present actions, other than the parallel testing.
I can understand, particularly for say "home-made" media, or based on experience of brand variations the advantage of doing some parallel testing intra-batch. Maybe on a time-based program, eg weekly, monthly ? It also obviously relates to how frequently you start new batches of media and maybe on the nature of your samples / tests.
Hope the above is helpful. Pls revert if any queries.
Rgds / Charles.C
PS -This is IMO a rather impressive SOP for the topic under discussion. Note the comments on testing procedures Pgs 4-9 and associated Appendices.
SOP Quality Control Culture Media, 2012.doc 2.47MB