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• Anaerobic Systems
• Antibiotic Sensitivity Testing
• Culture Media, Supplements and Raw Materials
• • Are there any guidelines for preparation and reconstitution of culture media?
  • Are there any guidelines for sterilising culture media?
  • Can I prepare culture media in a microwave?
  • Can I store selective supplements after reconstitution?
  • How can I re-melt solid media?
  • How long can I store culture media after preparation?
  • How should I dispose of used culture media?
  • How should I test the pH of culture media?
  • My culture medium does not look right - what has gone wrong?
  • My culture medium is not performing correctly - what has gone wrong?
  • Should I boil media before autoclaving?
  • What are the main components of culture media?
  • What exactly is agar?
  • What grade of water should I use to prepare culture media?
  • What is the shelf life of dehydrated culture media after the pot has been opened?
  • What quality control testing should I carry out on culture media?
  • Which blood product should I choose to make blood agar?
• Diagnostic Reagents
• Dipslides
• General
• Toxin Detection

USER-LABORATORY QUALITY CONTROL TESTS ON PREPARED MEDIA

Quality control tests should be carried out by the end-user laboratory to ensure that the performance characteristics of the medium are within specification and that the methodology of medium preparation is satisfactory.

Each lot/batch of prepared medium should be subjected to a minimal testing programme which will ensure that it is acceptable and will demonstrate a typical bacterial performance.

1 pH value: check that the pH of the prepared medium, when tested in final form at ambient temperature (25°C) lies within the range given on the product label. The medium should be discarded if the pH value lies outside the specified range.

2 Sterility: a representative sample of each lot/batch of medium should be incubated for 2-5 days at 35-37°C. As a general rule, for a lot of 100 or less units a 3-5% sample should be tested. For a larger lot, 10 random plates or tubes are taken. There should be no evidence of microbial growth after incubation. Discard all sterility samples when the tests have been completed.

3 Growth performance: test the growth support properties of the product by inoculating the medium with appropriate stock cultures and/or fresh isolates. Use a standard inoculation procedure and examine the quantitative and qualitative results obtained. If testing new lots/batches of media, inoculate old and new lots in one test and compare the performance of the two lots side by side.

4 Stability: periodically perform the above procedures on stored prepared media in order to determine whether the storage conditions will give optimal results.

NOTE: If a medium does not perform to expectations and all the manufacturer's recommendations have been followed, then the following steps should be taken:

1 Record the nature of the problem and the method of preparation of the medium.
2 Note the lot/batch number and the date it was received.
3 Call the Technical Support department of the company.