Abstract
Background: Bacteria used as indicators for pathogenic microorganisms in water are not
considered adequate as enteric virus indicators. Surface water from a tropical high-altitude system
located in Mexico City that receives rainwater, treated and non-treated wastewater used for
irrigation, and groundwater used for drinking, was studied.
Methods: The presence of enterovirus, rotavirus, astrovirus, coliphage, coliform bacteria, and
enterococci was determined during annual cycles in 2001 and 2002. Enteric viruses in concentrated
water samples were detected by reverse transcriptase-polymerase chain reaction (RT-PCR).
Coliphages were detected using the double agar layer method. Bacteria analyses of the water
samples were carried out by membrane filtration.
Results: The presence of viruses and bacteria in the water used for irrigation showed no
relationship between current bacterial indicator detection and viral presence. Coliphages showed
strong association with indicator bacteria and enterovirus, but weak association with other enteric
viruses. Enterovirus and rotavirus showed significant seasonal differences in water used for
irrigation, although this was not clear for astrovirus.
Conclusion: Coliphages proved to be adequate faecal pollution indicators for the irrigation water
studied. Viral presence in this tropical high-altitude system showed a similar trend to data
previously reported for temperate zones.