Other Methods Used for Bacterial Characterization

Tissue culture of susceptible mammalian cells may be used to characterize some bacteria by the toxins they produce. For example, Shiga-like toxins (verotoxins) are produced by E. coli 0157 H7.4,8 

Several additional instrumental techniques have also been developed for bacterial characterization. Capillary electrophoresis of bacteria, which requires little sample preparation,42 is possible because most bacteria act as colloidal particles in suspension and can be separated by their electrical charge. Capillary electrophoresis provides information that may be useful for identification. Flow cytometry also can be used to identify and separate individual cells in a mixture.11,42 Infrared spectroscopy has been used to characterize bacteria caught on transparent filters.113 Fourier-transform infrared (FTIR) spectroscopy, with linear discriminant analysis and artificial neural networks, has been adapted for identifying foodbome bacteria25,113 and pathogenic bacteria in the blood.5 

The total proteins synthesized by bacteria grown under standard conditions, when analyzed by polyacrylamide gel electrophoresis (PAGE), form patterns that can be compared to those of known strains by visual or computer-assisted 

Some nucleic acid-based techniques that are useful for epidemiological studies are amplified ribosomal DNA restriction analysis (ARDRA),17,79 ribo- 

We thank Carl E. Cerniglia, Robert H. ffeflich, and Donald D. Paine for their useful comments on the manuscript. The views presented in this article do not necessarily reflect those of the Food and Drug Administration. 

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