DETECTION OF SMALL ROUND STRUCTURED VIRUSES IN CLINICAL AND ENVIRONMENTAL-SAMPLES BY POLYMERASE CHAIN-REACTION

Norwalk (NV) and other small round structured viruses (SRSVs) have bee n identified as common causes of gastroenteritis. Outbreaks of Norwalk gastroenteritis have been associated with contaminated drinking water and food such as oysters and salads. The cloning and sequencing of th e NV genome has made it possible to detect NV and related viruses by t he reverse transcription polymerase chain reaction (RT-PCR). We applie d RT-PCR to detect SRSVs in faecal specimens from two gastroenteritis outbreaks in South Africa, designated ''Christmas'' and ''Grootbrak'' and were able to detect SRSVs in all of the three specimens from the C hristmas outbreak and in two of 16 specimens from the Grootbrak outbre ak. The RT-PCR procedure used appeared to be more sensitive for the de tection of SRSVs in patient stool specimens than immune electron micro scopy and NV antigen detection by enzyme linked immunosorbent Essay. T he RT-PCR procedure proved suitable for the detection of SRSVs in seed ed samples of sewage, sewage sludge, river water, and tap water. Howev er, sensitivity was lower for seeded samples of sewage and sludge than for tap water, which indicates interference by high levels of organic matter. The RT-PCR procedure was also used to show that small numbers of SRSVs can successfully be recovered from large volumes of water by means of a glass wool adsorption-elution method. Since-no practical m ethod is available for quantitation of the small numbers of SRSVs conc erned, it was not possible to evaluate the efficiency of recovery. Alt hough no SRSVs have been detected by direct testing of sewage and slud ge samples, the results obtained in this study show that RT-PCR detect ion of SRSVs sewage and polluted water environments is feasible, and t hat small numbers of the viruses can, like many other enteric viruses, successfully be recovered by means of a glass wool adsorption-elution method.