AWWA PATH56525

Difficulties in the replication of human astrovirus in cell cultures have led to the use of diagnostic procedures such as electron microscopy, ELISA or RT-PCR, which fail to provide quantitative data in environmental samples. The development of a sensitive competitive RT-PCR assay for the quantification of human astroviruses based on the use of an internal control is described (Caballero et al, 2002). The technique has been used to quantify astroviruses in sewage samples before and after treatment in three wastewater treatment plants and in river water samples before (Nile water) and after (drinking water) treatment in three water treatment plants in the Cairo area (Egypt) over one year (November 1998-October 1999). The positive samples were assayed by an CC-RT-PCR (Cell Culture-RT-PCR), using the CaCo-2 cell line (Pinto et al, 1994; Abad et al, 1997), to determine the infectious viruses in reference to the number of viral genomes obtained by the competitive RT-PCR. In this study, a competitive RT-PCR using an internal control was introduced to quantify astroviruses in sewage and water samples before and after treatment, collected from greater Cairo. Astroviruses were quantified in all the sewage samples, which were positive by RT-PCR and in the two positive water samples. A high number of RNA copies of astrovirus were observed in the end of autumn and in winter months in raw sewage of both Balaks and Zenin wastewater treatment plants. The gradual decrease of the RNA copies of astrovirus which was observed in the raw sewage since November 1998 until January 1999 may be due to the decrease of viral particles which were excreted from the sources of infection and the effect of environmental factors on the virus survival. The reduction in RNA copies in Balaks was of 1 log, 3 logs and >3 logs in December 1998, January 1999 and May 1999 respectively, and the reduction in the number of infectious particles was of 1 log. Using this competitive RT-PCR, equal amounts of RNA could be quantified before and after treatment in Mostorod WTP (2.3X103 RNA copies/l) in June 1999, but using CC-RT-PCR, there was 1.25X100 CC-RT-PCRu/l in raw water while no infectious particles were observed at all after treatment. This plant uses chlorine at 1-1.5 mg/l as a final step in the treatment and although astroviruses are not completely inactivated by chlorine, reduction levels of 4 and 2.4 logs with 1mg/l or 0.5 mg/l of free chlorine respectively after 2 hours of treatment have been described (Abad et al, 1997). The use of this internal control to quantify the physical particles or the use of a CC-RT-PCR technique to quantify the infectious viruses give the chance for recognition of the capability of both wastewater and water treatment plants to remove astroviruses. Includes 4 references, table.

Product Details

Edition:

Vol. - No.

Published:

09/22/2002

Number of Pages:

4

File Size:

1 file , 110 KB