Search

The bacteriophages of E. faecalis strains AIM06 (DSM100702) and SR14 (DSM100701) have previously been validated as human-specific microbial source tracking (MST) markers in Thailand. In this study, their spatial and temporal distribution in a freshwater river was investigated for the first time (n = 48). The abundance of enterococci as a standard microbial water quality parameter was evaluated by both the qPCR detection assay with primers and a hydrolysis probe according to the US EPA Method 1611 and the US EPA Method 1600 membrane filtration culture method. AIM06 and SR14 phages were detected by a double layer agar assay and were present in 87.5% and 81.3% of all samples with a co-presence of 92.9% of phage-positive samples. After spiking the representative phages, the ranges of recovery efficiencies were 57.9-99.6% and 49.6-99.9% (n = 48) for AIM06 and SR14 phages, respectively. The absolute abundance of AIM06 and SR14 phages ranged from 0.25 to 221.94 and from 0.25 to 76.66 PFU/100 mL, respectively. Enterococci DNA copies and CFU were detected in all samples ranging from 3.24 to 6.32 log10 copies/100 mL and 100.00 to 1593 CFU/100 mL, respectively. Enterococci in the qPCR assay also showed a moderate correlation with the culture method. The AIM06 and SR14 phage results indicated continuing human faecal pollution along the river with no significant different levels among stations. Interestingly, the higher levels of enterococci in downstream stations for both the qPCR and culture methods along with the significant correlation with other faecal indicator organisms and non-human MST markers implied non-human faecal pollution. In conclusion, this study provides insightful information that could lead to effective water quality management and public health risk reduction from exposure to faecally-contaminated water., Competing Interests: Declaration of competing interest The author(s) declare(s) that there is no conflict of interest regarding the publication of this article., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Coastal water quality is deteriorating worldwide. Water quality monitoring is therefore essential for public health risk evaluation and the management of water bodies. This study investigated the feasibility of using bacteriophages of Enterococcus faecalis as sewage-specific faecal indicators, together with physicochemical (dissolved oxygen, pH, temperature and total suspended solids) and biological parameters, to assess coastal water quality using multivariate analysis incorporating non-detects. The principal component and cluster analyses demonstrated that coastal water quality was mostly influenced by biological parameters, including Escherichia coli and total coliforms, which were found in all 31 sampling sites, and enterococci, which was found in all but two sampling sites. The enterococcal bacteriophages AIM06 and SR14 were detected in 17 and 18 samples at concentrations up to 1,815 and 2,790 PFU/100 mL, respectively. Both bacteriophages co-presented in approximately 80% of phage-positive samples, and the concentrations at each site were not significantly different. Overall, either bacteriophage could be used to differentiate high- and low-level coastal water pollution, as grouped by cluster analysis. This study is the first to investigate the suitability of sewage-specific bacteriophages of E. faecalis for monitoring coastal water quality and emphasises the importance of a multivariate analysis with non-detects to facilitate coastal water quality monitoring and management.