Enterococcus phages as potential tool for identifying sewage inputs in the Great Lakes region

Bacteriophages are viruses living in bacteria that can be used as a tool to detect fecal contamination in surfacewaters around the world. However, the lack of a universal host strain makes them unsuitable for tracking fecalsources. We evaluated the suitability of two newly isolated Enterococcus host strains (ENT-49 and ENT-55)capable for identifying sewage contamination in impacted waters by targeting phages specific to these hosts.Both host strainswere isolated fromwastewater samples and identified as E. faeciumby 16S rRNA gene sequencing.Occurrence of Enterococcus phages was evaluated in sewage samples (n=15) fromfive wastewater treatmentplants and in fecal samples from twenty-two species of wild and domesticated animals (individualsamples; n=22). Levels of Enterococcus phages, F+ coliphages, Escherichia coli and enterococci were examinedfrom four rivers, four beaches, and three harbors. Enterococcus phages enumeration was at similar levels(Mean = 6.72 Log PFU/100 mL) to F + coliphages in all wastewater samples, but were absent from all nonhumanfecal sources tested. The phages infecting Enterococcus spp. and F + coliphages were not detected inthe river samples (detection threshold b 10 PFU/100 mL), but were present in the beach and harbor samples(range = 1.83 to 2.86 Log PFU/100 mL). Slightly higher concentrations (range = 3.22 to 3.69 Log MPN/100 mL) of E. coli and enterococci when compared to F + coliphages and Enterococcus phages, were observedin the river, beach and harbor samples. Our findings suggest that the bacteriophages associated with theseparticular Enterococcus host strains offer potentially sensitive and human-source specific indicators of entericpathogen risk.