Prevalence and characterization of Escherichia coli isolated from the Upper Oconee Watershed in Northeast Georgia

PLoS One. 2018 May 8;13(5):e0197005. doi: 10.1371/journal.pone.0197005. eCollection 2018.

Abstract

Surface waters are important sources of water for drinking, industrial, agricultural, and recreational uses; hence, contamination of water by fecal, pathogenic, or antimicrobial resistant (AR) bacteria is a major environmental and public health concern. However, very little data is available on prevalence of these bacteria in surface water throughout a watershed. This study aimed to characterize Escherichia coli present in the Upper Oconee Watershed, a mixed-use watershed in Athens, GA, USA for potential pathogenicity and AR. E. coli were enumerated by colony counts, cultured by enrichment and direct plating, and characterized by phylo-groups, diarrheagenic pathotypes, and antimicrobial susceptibility. From the analysis, 99.3% (455/458) of the total samples were positive for E. coli resulting in 496 isolates. E. coli counts were as high as 1.2×104 CFU/100 ml, which is above the United States Environmental Protection Agency (U.S. EPA) threshold for recreational water (235 CFU/100 ml based on a one-time measurement). Phylo-groups B2 (31.7%; 157/496) and B1 (30.8%; 153/496) were the most prevalent among the isolates. Enteropathogenic E. coli (EPEC) (19/496) and Shiga toxin-producing E. coli (STEC) (1/496) were the only diarrheagenic pathotypes detected. AR was observed in 6.9% (34/496) of the isolates, 15 of which were multidrug resistant (MDR; resistance to two or more classes of antimicrobials). Tetracycline resistance was most often detected (76.5%; 26/34), followed by ampicillin (32.4%; 11/34), streptomycin (23.5%; 8/34), sulfisoxazole (23.5%; 8/34), and nalidixic acid (14.7%; 5/34). Results from this study showed that E. coli is prevalent in high levels in the Upper Oconee Watershed, suggesting possible widespread fecal contamination. The presence of pathogenic, AR E. coli in the watershed indicates that environmental water can serve as a reservoir of resistant bacteria that may be transferred to humans through drinking and recreational activities.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ampicillin / pharmacology
  • Anti-Bacterial Agents / pharmacology
  • Drug Resistance, Multiple, Bacterial / genetics*
  • Enteropathogenic Escherichia coli / isolation & purification*
  • Enteropathogenic Escherichia coli / pathogenicity
  • Escherichia coli Infections / drug therapy*
  • Escherichia coli Infections / epidemiology
  • Escherichia coli Infections / microbiology
  • Georgia
  • Humans
  • Microbial Sensitivity Tests
  • Nalidixic Acid / pharmacology
  • Shiga-Toxigenic Escherichia coli / drug effects
  • Shiga-Toxigenic Escherichia coli / genetics
  • Shiga-Toxigenic Escherichia coli / pathogenicity
  • Water Microbiology*

Substances

  • Anti-Bacterial Agents
  • Nalidixic Acid
  • Ampicillin

Grants and funding

Funded by United States Department of Agriculture, Agricultural Research Service Intramural funding Project Number: 6040-32000-009-00 https://iapreview.ars.usda.gov/research/projects/projects.htm?ACCN_NO=430182. Centers for Disease Control and Prevention. Broad Agency Announcement to address antibiotic resistance, Agricultural Research Service Sub-Project Number: 6040-32000-009-08R https://www.cdc.gov/drugresistance/solutions-initiative/innovations-to-slow-AR.html.