Groundwater Pollution by Human and Animal Enteric Viruses

Abstract

Groundwater contamination is a growing problem in southeastern Minnesota. This region is characterized by karst topography which is responsible for the formation of sinkholes, subsurface cracks, and underground rivers. These features enhance transportation of surface contaminants into groundwater. The present study was conducted to determine the presence of viruses, coliforms, fecal coliforms and coliphages in private rural wells situated in this region. Another purpose was to study the occurrence of drug resistance in bacteria isolated from groundwater. A total of 268 water samples was collected from 26 different sites over a period of 34 months. Coliform bacteria were detected at least once from 22 of the 26 sites. Human enteric viruses were detected in 9 groundwater samples collected from 7 different sites, some in the absence of fecal coliforms. A total of 161 samples was tested for the presence of coliphages. Of these, 13 samples from 7 sites were found positive. On two occasions, coliphages were isolated from samples in which coliforms were undetectable. Water from 10 sites yielded drug resistant indicator bacteria. Twenty-five of 38 (65.8%) total coliforms and 9 of 27 (33.3%) fecal coliforms tested were found to carry drug resistance.