Understanding genetic diversity of Escherichia coli within recycled water systems

Treatment and recycling of wastewater derived from treatment plants offers a cost-efficient supply that decreases demands on natural water resources. In Victoria, recycled water is treated to either Class A, B or C standards. Class A water is the highest quality achievable and only grade suitable for non-potable residential applications.

Escherichia coli inhabit the lower intestinal track of warm-blooded mammals and were believed to enter the environment through faecal contributions. Both commensal (non-pathogenic) and pathogenic sub-types of the species have been described with over 700 serotypes. Consequently, E. coli is applied as a faecal indicator a part of recycled water guidelines for regulatory classification of water quality and class. However, evidence has demonstrated increasing rates of E. coli survival and multiplication within a range of environments. Compromising its application as a faecal indicator.

Phylogenetic analysis of E. coli strains demonstrated divergent lineages, with environmental isolates belonging to distinct clades. Gene level differences were also identified. However, it is noted that this study contained only a limited number of isolates, with broader species level analysis required. Therefore, this study will undertake comparative genomic analysis to understand the phylogenetic diversity of E. coli from raw water to post treatment. This will aid in determining if genetic lineages of E. coli are retained through processing and if these strains display are representative of a single, or multiple, phylogenetic lineage.