What is the Meaning of passage?
- Whenever viable organisms growth on fresh medium is called passage (transfer of organisms grow on fresh medium), either on solid agar or in broth.
- Sub-culturing is considered to be a transfer/ passage.
- Freeze-dried cultures by thawing or rehydrating is not a passage.
- It means solid media to liquid media or liquid media to semi solid media transfer not a passage, every transfer of organisms grow on fresh medium is called passage. It means new generation.
- Every organism multiplication (generation) some time required, at least that time your providing for organism multiplication (generation) is called passage.
- The USP recommends Seed lot system is better for microbial culture maintenance.
- Microbial cultures are commercially available.
- Cultures are used in performance testing of products, as possitive and negative controls, as indicator organisms and identification standards.
- Culture are called different names control strains, standard cultures, reference strains, test strains and quality control strains. These terms are generally be used interchangeablly, though the performance seems to be reference strains or reference culture.
How many Passages are acceptable in the laboratory?
- As per USP general chapter 51 (Antimicrobial Effectiveness Testing) says, The viable microorganisms used in the test must not more than five passage removed from the original strain.
- Because increasing passages (more than five passages) are cause to phenotypic variations, genetic drift, mutation and risk of contamination.
- Frozen cultures should be stored at -30 degree C or below, until use. If stored at -70 degree C or below in lyophilized form. Slants may be stored at 2 to 8 degree C for up to a week.
