Numerous microbiological methods can be considered "rapid" in comparison with traditional ones. These range from techniques that can give results within a few minutes, to those that give results within approximately 24 hours. Not all may be commercially available; some are more suited to research facilities, because they are either too complex or insufficiently robust for routine use within a quality-control environment.
Before contemplating the use of a rapid method it is worth quickly reviewing why a rapid method might be selected. The pharmaceutical and medical-device industries traditionally achieved their competitive edge by the innovation of their product portfolio. While this is still the case, it has become increasingly more difficult to identify novel therapeutic compounds, and more expensive to bring to market. It is said that only one in every 10,000 compounds evaluated are ever commercialized, at a cost of between $250 to $500 million to the pharmaceutical industry.
Companies have therefore had to look at other areas to maintain profitability, including mergers or takeovers, centres of excellence, product portfolio rationalization, and customer service. It is the latter area that has promoted the use of rapid methods.
While most chemical analysis can produce results ranging from a few minutes to 24 hours, microbiological analysis takes between two to seven days (up to 14 days for sterility testing). Therefore rapid method introduction can significantly increase speed to market, release inventory faster, reduce warehouse storage capacity, and enable the market to be serviced more rapidly. Against this capital cost of the equipment required, and, invariably, the higher cost of associated consumables must be offset. However, where the product impacted is becoming increasingly more expensive, these costs can normally be amortized against the faster turnover of the inventory.
We have identified the principal rapid methods proposed for either identification or enumeration of microorganisms. Where the technique is either to the authors' knowledge not commercially available or suited to routine use, this is noted in the accompanying text. Identification methods specific for a single microorganism have not been included.
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