Specimen collection for electron microscopy.

analysis of PCR products amplified from five strains of spotted fever group Rickettsiae with Rr with Rr 190. synthase gene comparison, a new tool for phylogenetic analysis, and its application for the Rickettsiae. To the Editor: As virologists whose specialties include diagnostic electron microscopy (EM), we read with interest the discussion on bioterrorism scenarios (1,2) and the subsequent note by Marshall and Catton (3) on the rapid EM diagnostic process used for smallpox (1). EM diagnostics for viral agents offer an open, undirected view; a catch-all method; and speed. A negative stain preparation may be made and a result could be obtained within 5 minutes of the specimen's arrival in the EM laboratory. As suggested by Marshall and Catton, however, success depends as much on the quality of the sample collected as on the method of preparation and skill of the microscopist. provides EM viral diagnostic services for up to 800 specimens per year and counsels other German diagnostic units. The Electron Microscope Unit for the Department of Medical Microbiology and Infectious Diseases, University of Manitoba, is used for EM viral diagnos-tics by both the major health-care facility in Manitoba, Canada, and the Manitoba Provincial Laboratories; it examines approximately 2,300 clinical specimens annually. Our two facilities examine 70 to 90 vesicular specimens of suspected viral origin annually. In our experiences, the most effective methods of specimen collection from virus-induced blisters (or ulcers) involve opening the vesicle with a 26-gauge needle. The exudate may then be collected and prepared for examination in one of three ways: 1) Draw lesion aspirates into the barrel of the needle with a tuberculin syringe and cap the needle (4); 2) touch a light microscope slide to the vesicle fluid; or 3) touch a 400-mesh, plastic coated specimen grid directly to the base of the lesion (5). The samples may then be transported to an EM facility for preparation and examination. With the first two sample types, the sample is resuspended in approximately 20 µL of 0.2-µ pore-filtered, bidistilled water; this suspension is used to prepare a standard drop preparation on a 400-mesh, carbon-reinforced, plastic-coated grid. In all cases, the specimens are then negatively stained and examined. Because of safety concerns about HIV infection, many health officials view transport of vesicle aspirates in capillary pipettes or needles as unacceptable. Glass slides are considered more acceptable, but still a risk. Since examination facilities or wards usually do …