A review of Mansilha CR, Coelho CA, Reinas A, Moutinho A, Ferreira S, Pizarro C, Tavares A. 2010. Salmonella: The forgotten pathogen: Health hazards of compliance with European Bathing Water Legislation. Marine Pollution Bulletin. 60:819-826.
Coastal water have the potential to be polluted via industrial, urban and agricultural effluents including sewage. These effluents contain both non-pathogenic and pathogenic bacteria which have been shown to be the cause of several human diseases including cholera, hepatitis and meningitis. These bacteria come into contact with humans when bathing in infected waters and can enter via the oral route, ears, eyes, nose or respiratory tract. There is obviously a need to monitor popular bathing waters is to determine their safety for recreational use.
Currently the European Bathing Water Directive 2006 determines water quality based on data compiled over four bathing seasons with different standard for coastal and marine waters. However the monitoring of pollutions is based on the non-pathogenic indicator bacteria Escherichia coli and intestinal enterococci. These are used as faecal indicators, the presumption of which is that the water is polluted. This argument has been question by many papers however.
Salmonella spp. is a common and widely distributed human pathogen that is not only the most commonly recorded cause of gastroenteritis but can also lead to far more serious illness such as typhoid. Due to this organisations such as the WHO recommend the regular screening of Salmonella in all bathing waters, advice which is rarely followed. The assumption that when there are high levels of faecal indicator species that Salmonella will also be present is agreed by many authors, but perhaps more importantly, some studies have found Salmonella in the absence of faecal indicators.
The aim of this study was to assess links between the presence of faecal indicator species and the presence of Salmonella. By assessing the water quality using both new faster techniques and standard ISO 6340:1995 techniques differences could be inferred. Samples were collected from Northern Portugal from terrestrial freshwaters, coastal waters and transitional waters.
This study identified Salmonella spp. in 23.1% of samples with 15.6% of coastal waters being Salmonella positive. Within all samples 35 different Salmonella serotypes were identified. Within marine waters the most frequent serotype was Salmonella typhimurium which accounted for 15.6%. This is important as it is this serotype that can cause typhoid and typhoid fevers.
When samples were first classified according to the EU directive and then compared with the presence of Salmonella, there were significant correlations between indicator species and Salmonella when classified as “poor” or “sufficient”. However when waters were classified as “good” and “excellent” there was a lack of correlation, if any at all. This was due to Salmonella being present in these waters when there were very low levels of faecal indicators. 9.3% of “Excelelnt” waters contained Salmonella and 14.4% of good.
This occurrence has been linked to episodic rainfall and runoff events by other authors. In this study those beaches that experienced Salmonella but low faecal indicators were indeed in areas fed by substantial amounts of runoff.
This demonstrates clearly that the indicators used to determine water quality are not always adequate for the prediction of pathogens and the use of only two indicators is not sufficient to protect the health of recreational water users. Whilst this study demonstrates the need for more stringent bathing water regulations, it recognises that more research into salinity differences and epidemiological studies are needed to identify the source of potential pathogens and the significance of the presence of these in terms of affecting human health.
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