This study suggests conducting an epidemiological study in wide geographical areas of different EU countries on different faecal pollution scenarios (such as point sources, animal sources, and agricultural sources) for evaluating the best faecal indicators and their guideline values (Fujioka et al. 2015). Further, simultaneously monitoring of different microbial targets, such as current FIB, their molecular markers, MST marker, viral indicators, and protozoan indicators may demonstrate the relation between chances of illness on the different enumeration levels of faecal targets for evaluating the best indicator in different pollution scenarios. Also, future research should include quantitative microbial risk assessment approaches for es-timating the illness risk of enteric pathogens in bathing water, which has been dis-cussed elsewhere (Fujioka et al. 2015, Janne et al. 2017, Federigi et al. 2019).
WHO guidelines (2003, 2009) recommended the characterization of human health risks based on FIB enumeration and a sanitary survey. Also, EU has a good practice to require a bathing water profile for each bathing site, based on FIB counts, site inspection and identification of probable sources of contamination.
However, the process for preparing the survey or profile should be as objective as possible to avoid subjective risk factors interpretation. Further, instead of depend-ing solely on FIB counts, the survey could be supplemented by usdepend-ing host-specific qPCR based MST can assess the human health risk more accurately at bathing sites (Harwood et al. 2014, Nevers et al. 2020). The coupling of MST with currently used FIB for regulatory purposes can better protect the health of bathers (Haugland et al.
2010, Harwood et al. 2014, Nevers et al. 2020). Supplementing the analysis list is supported by the findings from an earlier study, which reported that the best faecal indicator evaluated for one bathing site might not be equally good for the next site (Griffith et al. 2016).
In addition to the microbiological safety of the water column, the microbial quality of beach substrates can have public health implications (Abdelzaher et al.
2010). The current bathing water regulations do not consider the microbial quality
69 of such substrates, such as sediments and vegetation (Weiskerger et al. 2019, Nevers et al. 2020). In the future, a more throughout bathing water profile could be created by analysing the microbial content of beach substrates together with the water sample testing.
Also the use of the high-throughput sequencing of taxonomic and functional genes can be useful for generating better knowledge to protect public health at beaches. This technology has been gradually developing. One trait could be the future development of it as a regulatory monitoring technology for the direct moni-toring of pathogens.
70
9 CONCLUSIONS
The Colilert-18 method produces an equivalent E. coli count to the reference method ISO 9308-3 1998 from bathing water samples in Finland; so, Colilert-18 can be used for the monitoring of bathing water quality for regulatory purposes.
The false-negative rate of Colilert-18 can be reduced by giving more atten-tion in laboratory practices, such as reading even a slight fluorescence in the Colilert wells as positive to E. coli and increasing the incubation time of the tray from 18 hours to 21 hours.
The ISO 7899-2 2000 method is sensitive and specific for enumerating intes-tinal enterococci from bathing water samples of Finland.
The analysis of multiple sample volumes in the enterococci enumeration is proposed to reach 10-100 colonies per membrane when 47 mm diameter membranes are used to prevent the overestimation of low counts and un-derestimation of the high counts.
About 93% of the confirmed intestinal enterococci with the ISO 7899-2 2000 method belonged to E. faecium and E. faecalis clades, according to the partial 16S rRNA gene sequencing.
The decay rate of E. faecalis, V. cholerae and MS2 coliphage varied among substrates: water, sediment, or vegetation.
E. faecalis decayed faster in water than in the sediment or vegetation.
A positive relation between culturable E. faecalis counts, V. cholerae gene copies and MS2 counts were recorded only during the first few days of a survival study.
In addition to bathing water, superficial sediment and aquatic vegetation are important substrates for the partitioning of enteric microbes at the beach environments.
The enumeration of the intestinal enterococci counts alone was not enough for predicting pathogens, such as enteric viruses and Vibrio spp. in bathing water.
The bacterial diversity, taxonomic variation and PHRB genera varied be-tween the sample collection sites and sampling seasons within a freshwater watershed.
The AGR process produces microbiologically stable and safe drinking wa-ter.
71
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