Frequency of preclumped virus in routine fecal specimens from patients with acute nonbacterial gastroenteritis

Abstract

A low-speed centrifugation technique for the preparation of grids after minimal purification of fecal extracts is described for examination of viruses by direct electron microscopy using negative staining. Results showed that adenovirus, astrovirus, rotavirus, and "small round" viruses were frequently shed into the gastrointestinal tract in clumps of variable size. Differential centrifugation study showed that a substantial proportion of the virus in the sample was lost in the initial pellet at the first step of clarification; this finding casts doubt on the validity of immune electron microscopy for direct typing of strains of these viruses from stools. In addition, particle counts based on conventional specimen processing are likely to grossly underestimate the true value.

Rotaviral and Coronaviral Diarrhea

“…This is an important step, because many enteric viruses are found to be present in large aggregates that could be pelle ted and discarded at higher centrifugal forces. 58 The low-speed supernatant is then transferred to ultracentrifuge tubes, and centrifuged at 100,000 x g for 60 minutes. The supernatant is decanted, the resulting pellet is saved and reconstituted in 0.5 ml of distilled water.…”

Diagnosis of Noncultivatable Gastroenteritis Viruses, the Human Caliciviruses

“…The pellet is suspended in a few drops of distilled water and negatively stained as for direct electron microscopy. The saline control is necessary to demonstrate the specificity of the immune serum because virus clumping may occur in the absence of antibody (56,194). A positive sample has aggregates of viral particles which are absent in the saline control sample.…”

Comparison between patients with norovirus‐related gastroenteritis and asymptomatic carriers with respect to distribution of antibody‐complexed viral particles and intestinal flora

“…2,3 Nevertheless, it should be noted that aggregated or assembled virus particles in fecal specimens, which seemed to bind to antibodies, had sometimes been observed by electron microscopy examination. 10 Indeed, acquired norovirus-specific antibodies in serum and IgA antibodies in breast milk were previously reported, 11,12 but information on fecal IgAs was limited. 13 The influence of the intestinal flora on norovirus infection was previously reported.…”