Microbiological Evaluation of Water Quality from Urban Watersheds for Domestic Water Supply Improvement

A. Mark Ibekwe, Shelton E. Murinda and Alexandria K. Graves
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A. Mark Ibekwe: U.S. Salinity Laboratory, USDA-ARS, 450 West Big Springs Road, Riverside, CA 92507, USA
Shelton E. Murinda: Department of Animal and Veterinary Sciences, California State Polytechnic University Pomona, 3801 West Temple Avenue, Pomona, CA 91768, USA
Alexandria K. Graves: Department of Soil Sciences, North Carolina State University, Williams Hall 3411E, P.O. Box 7619, Raleigh, NC 27695, USA

IJERPH, 2011, vol. 8, issue 12, 1-17

Abstract: Agricultural and urban runoffs may be major sources of pollution of water bodies and major sources of bacteria affecting the quality of drinking water. Of the different pathways by which bacterial pathogens can enter drinking water, this one has received little attention to date; that is, because soils are often considered to be near perfect filters for the transport of bacterial pathogens through the subsoil to groundwater. The goals of this study were to determine the distribution, diversity, and antimicrobial resistance of pathogenic Escherichia coli isolates from low flowing river water and sediment with inputs from different sources before water is discharged into ground water and to compare microbial contamination in water and sediment at different sampling sites. Water and sediment samples were collected from 19 locations throughout the watershed for the isolation of pathogenic E. coli . Heterotrophic plate counts and E. coli were also determined after running tertiary treated water through two tanks containing aquifer sand material. Presumptive pathogenic E. coli isolates were obtained and characterized for virulent factors and antimicrobial resistance. None of the isolates was confirmed as Shiga toxin E. coli (STEC), but as others, such as enterotoxigenic E. coli (ETEC). Pulsed field gel electrophoresis (PFGE) was used to show the diversity E. coli populations from different sources throughout the watershed. Seventy six percent of the isolates from urban sources exhibited resistance to more than one antimicrobial agent. A subsequent filtration experiment after water has gone through filtration tanks containing aquifer sand material showed that there was a 1 to 2 log reduction in E. coli in aquifer sand tank. Our data showed multiple strains of E. coli without virulence attributes, but with high distribution of resistant phenotypes. Therefore, the occurrence of E. coli with multiple resistances in the environment is a matter of great concern due to possible transfer of resistant genes from nonpathogenic to pathogenic strains that may result in increased duration and severity of morbidity.

Keywords: pathogenic Escherichia coli; indicator bacteria; surface water; sediment; contamination; watershed (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2011
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