Improved detection of viruses by electron microscopy after direct ultracentrifuge preparation of specimens

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Abstract
The Beckman Airfuge air turbine ultracentrifuge and the new EM-90 particle-counting rotor were adapted to improve detection by EM of viruses in clinical specimens. Samples were clarified by centrifugation, pelleted in the EM-90 rotor directly to Formvar-coated Cu grids and stained with 1.5% sodium phosphotungstate. Virus counts and endpoint titrations of serial dilutions of partially purified preparations of poliovirus, SA11 rotavirus, herpes simplex virus and vaccinia virus showed an increase of .apprx. 1.5 to 3.0 log10 over the virus titers of unconcentrated preparations of the same material. An increased yield of 14% more positive specimens for rotavirus was obtained after preparation of clinical samples by direct ultracentrifugation vs. a method without virus concentration (82 vs. 72). A prospective study showed that detection of adenoviruses, herpesviruses and enteroviruses increased when specimens were prepared by direct ultracentrifugation. Direct ultracentrifugation with the EM-90 rotor in the Airfuge ultracentrifuge is a rapid concentration method which enhances the rate and yield of virus detection from clinical specimens by EM and is easily adaptable to a diagnostic virology laboratory.