Electron microscopy of stool-shed viruses: retention of characteristic morphologies after long-term storage at ultralow temperatures.

Storage of stool specimens at -70 degrees C has been reported to destroy the characteristic morphology of calicivirus. To determine if other stool-shed viruses are similarly affected, stool specimens previously examined by electron microscopy and observed to contain virus particles were reexamined after 6-10 years of storage at -70 degrees C to -85 degrees C. The stools contained virus particles of different morphological types, including astrovirus, small round structured virus, adenovirus, and rotavirus as well as calicivirus. Also reexamined were stools containing coronavirus-like particles and T = 19 virus-like particles. Characteristic virus particles, including calicivirus particles, were recognized in all the stools reexamined. The results indicate that long-term storage of stools at ultralow temperatures does not present a significant problem for the morphological identification of stool-shed viruses.