Water Quality Assessment: Endotoxin Brings Real-Time Measurements and Non-Faecally Transmitted Bacteria to the Table

We have used a rapid, portable assay (Bacterisk) to determine the bacterial water quality along several inland waters in SW England. Water samples were compared by a conventional membrane filter and culture methods for faecal indicator bacteria (FIB; E. coli and enterococci) and endotoxin measurement by Bacterisk. The Bacterisk data, measured in near-real-time, correlate well with both E. coli and enterococci, but also allow the presence of potential pathogens of a non-faecal origin to be detected. The sensitivity was calculated to be 92.96% with a specificity of 46.3% for E. coli with an expanded uncertainty of 22.07% and an Endotoxin Risk detection limit of 25 units. The presence of Bacterisk detectable non-faecal pathogenic bacteria in the water samples was successfully confirmed by Illumina MiSeq sequencing followed by target species-specific qPCR. Sequencing showed the presence of pathogens including Pseudomonas aeruginosa, Salmonella typhi, Acinetobacter baumannii, Shigella spp., and Legionella spp. as well as antimicrobial resistance genes. Furthermore, the portable Bacterisk assay was able to acquire data on the water quality from different locations and at different time points, providing a comprehensive surveillance tool that challenges the time to results by conventional methods (minutes instead of days), yielding compatible results.