Reference cultures and plant isolates have an important role in disinfectant testing and selection, validation protocols and environmental monitoring. NCIMB’s CEO Dr Carol Phillips looks at best practices for maintaining and preserving them.
Effective cleaning, disinfection and environmental monitoring of production plants are essential processes for manufacturers from a range of industry sectors and reference cultures play an integral part in the procedures that are involved in these processes. They are used for the preparation of quality control (QC) cultures used to test the efficacy of disinfectants and for QC of media used in environmental monitoring (EM) programmes, as well as providing a resource for tracing sources of contamination. Their vital role in ensuring the quality of products makes it important that the production, maintenance and preservation of reference strains are carried out to a high standard.
QC cultures
It is obviously key that culture media used in plant EM programmes are capable of consistently supporting growth of micro-organisms. For example, with respect to the EM of cleanrooms in vaccine manufacturing facilities, the World Health Organisation (WHO) states that the growth promotion properties of media used in EM programmes should be tested for a predefined list of organisms.1 This list should include a minimum of five unique microbial strains and the QC cultures used should be traceable to a recognised culture collection such as the UK’s National Collection of Industrial, Food and Marine Bacteria (NCIMB), the National Collection of Type Cultures, a culture collection of Public Health England (NCTC), or the American Type Culture Collection (ATCC).
Some labs may prepare QC cultures from reference strains for their own in-house use. One of the most important elements of maintaining any collection of reference cultures is ensuring the genetic stability of the strains within it, and continuous sub-culturing will generally give rise to a degree of genetic drift that will ultimately render the cultures unsuitable for use as QC strains. Consequently, it is good practice to ensure that working cultures are no more than five generations removed from the original reference culture or isolate, and to have a system for preserving and maintaining reference cultures with their original characteristics.
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