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In Microbiology and Infectious Disease Diagnostics: The Use of Scanning Electron Microscope

Ellen Barker

In early research, electron microscopy proved critical in identifying infectious illness causal agents. It is still an essential technique for diagnosing diseases and testing for microorganism identification. Negative staining for transmission electron microscopy (TEM) has traditionally been considered the "gold standard" for imaging microbiological samples, such as in diagnostic virology. Negative-stain TEM, on the other hand, need a sufficient concentration of bacterial cells or virus particles, as they are adsorbed to a thin support surface. Microbes must thus be grown to a high tire and/or concentrated by centrifugation, which is typically impossible with patient materials. As a result, for many sorts of microbiological studies, electron microscopy has historically had low test sensitivity. For TEM to identify agents such as poxviruses or polyomaviruses in patient specimens, a minimum concentration of 105 to 106 particles/ml is normally required. By contrast, the detection level of viruses utilizing culture or nucleic acid testing typically varies from 1 to 50 particles per assay. Because of recent advancements in filtering methods, TEM and SEM virus detection may now be performed with as few as 5000 total particles per sample. Furthermore, electron microscopy may be used to determine the kind of microbe present, typically down to the genus level, allowing additional specialized tests (such as primers or particular antibodies) to be used to properly identify the agents present.