Conventional and rapid analytical microbiology 191 colonies on the agar that are typical of the microorganism under test are described as presumptive colonies. In order to confirm that the colonies are composed of the test organism, further biochemical and serological tests are sually performed on pure cultures of the organism. This usually requires colonies from primary isolation plates being restreaked to ensure purity. The purified colonies are then tested biochemically by culturing in media that will indicate whether the organism produces particular enzymes or utilises certain At present a number of companies market miniaturised biochemical test systems that allow rapid or automated biochemical tests to be quickly and easily set up by microbiologists. Serological tests are done on pure cultures of some isolated organisms, e.g. Salmonella using commercially available antisera 8.4 Rapid and automated methods The general interest in alternative microbiological methods has been stimulated in part by the increased output of food production sites. This has resulted Greater numbers of samples being stored prior to positive release reduction in analysis time would reduce storage and warehousing costs a greater sample throughput being required in laboratories- the only way that this can be achieved is by increased laboratory size and staff levels, or by using more rapid and automated methods 3. A requirement for a longer shelf-life in the chilled foods sector-a reduction in analysis time could expedite product release thus increasing the shelf-life of the product 4. The increased application of HACCP procedures- rapid methods can be used in HACCP verification procedures There are a number of different techniques referred to as rapid methods and lost have little in common either with each other or with the conventional procedures that they replace. The methods can generally be divided into quantitative and qualitative tests, the former giving a measurement of the number of organisms in a sample, the latter indicating only presence or absence Laboratories considering the use of rapid methods for routine testing must carefully consider their own requirements before purchasing such a system Every new method will be unique, giving a slightly different result, in a different timescale with varying levels of automation and sample throughput. In addition, ome methods may work poorly with certain types of food or may not be able to detect the specific organism or group that is required. All of these points must be considered before a method is adopted by a laboratory. It is also of importance to ensure that staff using new methods are aware of the principles of operation of the techniques and thus have the ability to troubleshoot if the method clearly hows erroneous resultscolonies on the agar that are typical of the microorganism under test are described as presumptive colonies. In order to confirm that the colonies are composed of the test organism, further biochemical and serological tests are usually performed on pure cultures of the organism. This usually requires colonies from primary isolation plates being restreaked to ensure purity. The purified colonies are then tested biochemically by culturing in media that will indicate whether the organism produces particular enzymes or utilises certain sugars. At present a number of companies market miniaturised biochemical test systems that allow rapid or automated biochemical tests to be quickly and easily set up by microbiologists. Serological tests are done on pure cultures of some isolated organisms, e.g. Salmonella using commercially available antisera. 8.4 Rapid and automated methods The general interest in alternative microbiological methods has been stimulated in part by the increased output of food production sites. This has resulted in 1. Greater numbers of samples being stored prior to positive release – a reduction in analysis time would reduce storage and warehousing costs. 2. A greater sample throughput being required in laboratories – the only way that this can be achieved is by increased laboratory size and staff levels, or by using more rapid and automated methods. 3. A requirement for a longer shelf-life in the chilled foods sector – a reduction in analysis time could expedite product release thus increasing the shelf-life of the product. 4. The increased application of HACCP procedures – rapid methods can be used in HACCP verification procedures. There are a number of different techniques referred to as rapid methods and most have little in common either with each other or with the conventional procedures that they replace. The methods can generally be divided into quantitative and qualitative tests, the former giving a measurement of the number of organisms in a sample, the latter indicating only presence or absence. Laboratories considering the use of rapid methods for routine testing must carefully consider their own requirements before purchasing such a system. Every new method will be unique, giving a slightly different result, in a different timescale with varying levels of automation and sample throughput. In addition, some methods may work poorly with certain types of food or may not be able to detect the specific organism or group that is required. All of these points must be considered before a method is adopted by a laboratory. It is also of importance to ensure that staff using new methods are aware of the principles of operation of the techniques and thus have the ability to troubleshoot if the method clearly shows erroneous results. Conventional and rapid analytical microbiology 191