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United States Department of Agriculture

Agricultural Research Service

Research Project: Protection of Food and Water Supplies from Pathogen Contamination Title: Microbiological evaluation of water quality from urban watersheds for domestic water supply improvement

Authors
item Ibekwe, Abasiofiok
item Murinda, Shelton -
item Graves, Alexandria -

Submitted to: International Journal of Environmental Research and Public Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 25, 2011
Publication Date: November 30, 2011
Citation: Ibekwe, A.M., Murinda, S.E., Graves, A.K. 2011. Microbiological evaluation of water quality from urban watersheds for domestic water supply improvement. International Journal of Environmental Research and Public Health. 8:4460-4476.

Interpretive Summary: Santa Ana River is critical for replenishment of Orange County’s Groundwater Basin since over 2 million residents in Orange County depend on groundwater for 75 percent of their water supply. Any factor in the watershed which degrades the river affects the quality of the source water. In many watersheds, sources of water quality degradation may be from human, farm animals, wildlife, and pets, etc. The goals of this study were to determine the distribution of pathogenic E. coli as it relates to their pathways to source water that may affect water quality within the Santa Ana River watershed and to characterize them based on their genetic profiles and their resistances to some antibiotics. None of the isolates was confirmed as E. coli O157, but as other types of E. coli that are not as pathogenic as E. coli O157. The issue is that the presence of high proportion of antibiotic resistant non pathogenic E. coli in this watershed is a matter of great concern because of possible transfer of resistant genes from nonpathogenic to pathogenic E. coli which may lead to increased duration and severity of morbidity. The results of this research will be used by water quality managers from different water districts, researchers, and EPA for Total Daily Maximum Daily Load assessments for large and mixed watersheds.

Technical 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, 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 objectives of this study were to determine the influence of pollutant sources on water quality use for the prevention of salt water intrusion into domestic water supply and to examine the numbers of fecal bacterial composition in aquifer material impacted by contaminants from different sources. Water and sediment samples were collected from 20 locations throughout the watershed for the isolation of pathogenic E. coli. Heterotrophic bacteria and Escherichia 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 activities. 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) showed that E. coli populations from agricultural sources were different from the population from urban sources and diversity and antimicrobial activities were higher among isolates from urban sources. Seventy six percent of the isolates from urban sources exhibited resistance to more than one antimicrobial agent. 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.

Last Modified: 8/21/2014
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