Sunday, August 14, 2011

Laboratory Diagnosis of viral gastroenteritis: Rotavirus

• Collection of Specimens and Virus isolation
Many assays have been developed for the detection of rotavirus in stools. Specimens from 1- 4 day of illness are optimal for virus detection; however, shedding may continue up to 3 weeks, depending on the duration of symptoms. Viral shedding usually coincides with the duration of diarrhea, but diarrhea can continue for additional 2 - 3 days. Rotaviruses grow well in secondry monkey kidney cells and in immortalized monkey kidney cell lines in presence of trypsin (Estes, 2001).
Flowcytometry is another sensitive method for rotavirus detection (Barardi et al., 1999). It is also possible to recover rotaviruses from stool specimens directly in cell culture with reasonable efficiency. Growth of rotavirus in tissue culture makes possible the determination of virus serotype by neutralization assay and less often by Immune EM using serotype-specific MAbs (Yolken and Wilde, 1994).
• Electron Microscopy
EM allows quick identification of the Rotavirus particles in stool specimens. It had the advantage of high specificity because Rotaviruses have a distinctive morphology. Direct EM examination of stools permits detection of rotavirus in 80% to 90% of the virus-positive specimens. Immune EM is not necessary for the detection of Rotaviruses because the particle has such a distinct morphologic appearance (Desselberger and Dermody, 2005).

• Serologic diagnosis
There are a variety of techniques CF, IF, ELISA, neutralization, hemagglutination inhibition (Ishida et al., 1997). The method of choice in many laboratories is the confirmatory ELISA, because it is highly sensitive, does not require specialized equipment. Early diagnosis can be made by ELISA, which can detect a specific serum IgM response as early as 5 or 6 days after onset of illness (Kapikian, 1997).
• Molecular detection
The use of Rotavirus specific oligonucleotide primers in RT-PCR has allowed not only sensitive detection but also subgroup determination. For Rotavirus typing, RT-PCR has become the method of choice (Iturriza-Gomara et al., 2003).

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