Diversity of Escherichia coli in the Salish Sea: Potential Implications to Marine and Human Health

Abstract

E. coli is a species of enteric bacteria found in the intestinal tract of humans and animals that can also persist in the environment. Anthropogenic activity has led to opportunistic pathogenic E. coli from humans and animals contaminating environments through the discharge of fecal wastes in sewage and agricultural runoff. Studies of the diversity of E. coli found in environments near anthropogenic sources are needed to understand the risk to human and animal health. Gaps remain in scientific knowledge about E. coli diversity, survivability, and potential public health threats in marine environments. The Salish Sea is an area undergoing fast population growth with increasing nutrients and oxygen depletion due to the activity of wastewater treatment plants, and other human activity. The anthropogenic activity may impact the survivability and concentration of E. coli in the environment. We analyzed a dataset of 332 E. coli isolates from the Salish Sea ecosystem. A total of 196 multi-locus sequence types (ST) were identified from samples taken from marine water near shellfish beds, marine wildlife, river otters and a small number of freshwater samples from inlets into the Salish Sea. The isolates were compared to metadata for E. coli STs in EnteroBase, an international E. coli database. Additional information on E. coli STs was derived from searches of published studies in PubMed. We analyzed these data descriptively and spatially. Of the 196 ST in the data set, 80 (40.8%) did not have literature available in PubMed. For five STs: (5869, 1065, 11343, 9001, and 2164), no previous evidence of occurrence in marine water or sea mammals was identified. The greatest diversity of E. coli STs was found in the Strait of Juan de Fuca, an area which has wastewater treatment plants that dump partially treated wastewater into the Strait. These findings illustrate the diversity of environmental E coli in the marine environment and the need for further research the human and animal health implications of this diversity.