Advantages And Examples Of Commercial System Designs

Commercially available identification systems have largely replaced compilations of conventional test media and substrates prepared in-house for bacterial identification. This replacement has mostly come about because the design of commercial systems has continuously evolved to maximize the speed and optimize the convenience with which all four identification components shown in Figure 7-17 can be achieved. Because laboratory workload has increased, conventional methodologies have had difficulty competing with the advantages of convenience and updated databases offered by commercial systems. Table 13-1 lists and describes the most common manual and automated bacterial identification systems available.

Some of the simplest multitest commercial systems consist of a conventional format that can be

Figure 7-20 Plastic cards composed of multiple wells containing dried substrates that are reconstituted by inoculation with a bacterial suspension (bioMérieux, Inc., Hazelwood, Mo). Test results in the card wells are automadcally read by the manufacturer's reading device.

Hgjre M9 Biochemical test panel (API; bioMSrieux, Inc., Hazelwood, Mo). The lest results obtained with the substrates in each cupule are recorded, and an organism identification code is calculated by octal code conversion on the form provided. The octal profile obtained then is matched with an extensive database to establish organism identification.

Hgjre M9 Biochemical test panel (API; bioMSrieux, Inc., Hazelwood, Mo). The lest results obtained with the substrates in each cupule are recorded, and an organism identification code is calculated by octal code conversion on the form provided. The octal profile obtained then is matched with an extensive database to establish organism identification.

inoculated once to yield more than one result. By combining reactants, for example, one substrate can be used to determine indole and nitrate results; indole and motility results; motility, indole, and ornithine decarboxylase; or other combinations. Alternatively, conventional tests have been assembled in smaller volumes and packaged so that they can be inoculated easily with one manipulation instead of several. When used in conjunction with a computer-generated database, species identifications are made relatively easily.

Another approach is to have substrates dried in plastic cupules that are arranged in series on strips into which a suspension of the test organism is placed (Figure 7-19). For some of these systems, use of a heavy inoculum or use of substrates whose utilization is not dependent on extended bacterial multiplication allows results to be available after 4 to 6 hours of incubation.

Still other identification battery formats have been designed to more fully automate several aspects of the identification process. One example of this is use of "cards" that are substantially smaller than most microtitre trays or cupule strips (Figure 7-20). Analogous to the microtitre tray format, these cards contain dried substrates in tiny wells that are resuspended on inoculation.

Commercial systems are often categorized as either being automated or manual. As shown in Table 13-1, various aspects of an identification system can be automated and these usually include, in whole or in part, the inoculation steps, the incubation and reading of tests, and the analysis of results. However, no strict criteria exist that state how many aspects

Figure 7-20 Plastic cards composed of multiple wells containing dried substrates that are reconstituted by inoculation with a bacterial suspension (bioMérieux, Inc., Hazelwood, Mo). Test results in the card wells are automadcally read by the manufacturer's reading device.

must be automated for a whole system to be classified as automated. Therefore, whether a system is considered automated can be controversial. Furthermore, regardless of the lack or level of automation, the selection of an identification system ultimately depends on system accuracy and reliability, whether the system meets the needs of the laboratory, and limitations imposed by laboratory financial resources.

Overview of Commercial Systems

Various multitest bacterial identification systems (as listed in Table 13-1) are commercially available for use in diagnostic microbiology laboratories, and the four basic identification components outlined in Figure 7-17 are common to them all. However, different systems vary in their approach to each component The most common variations involve:

  • Types and formats of tests included in the test battery
  • Method of inoculation (manual or automated)
  • Required length of incubation for substrate utilization. This usually depends on whether utilization requires bacterial growth.
  • Method for detecting substrate utilization and whether detection is manual or automated
  • Method of interpreting and analyzing results (manual or computer assisted), and if computer assisted, the extent to which assistance is automated

The general features of some commercial identification systems are summarized in Table 13-1. More specific information is available from the manufacturers.

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Bacterial Vaginosis Facts

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