Traditionally, culture-based techniques have predominated when testing for bacteria. If an organism can grow in vitro, then it is viable and may constitute a threat to health or to the integrity of a product. Yet not all viable bacteria are currently capable of being cultured, and even if they cannot replicate on artificial media, they can retain cellular functions and thus may regain their ability to reproduce and thereby pose a health risk. Other organisms may only exist in a symbiotic relationship with another organism such as an amoeba in their natural habitat and thus may be undetectable in a standard culture-based test.
Methods based on culture will not detect viable, non-culturable bacteria, yet even if a bacterium can be cultured, it may only grow in specific conditions, within an optimum range of temperature, pH, osmotic conditions, and in the presence of the correct nutrients. Sub-optimal culture conditions may lead to false negatives in testing, with bacteria present in a sample unable to grow.
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