Towards the selection of the best discriminating parameters of microbial water quality: A case study of a urban recreational water resource involving a dam-rivers complex in Córdoba, Argentina

PAVAN J,; MASSACHESSI G,; BARRIL P,; MARTINEZ L,; GIORDANO M,; FERREYRA L,; ISA M.B,; WELTER A,; MARTINEZ WASSAF M,; RÉ VE,; NATES SV,

Barcelona

Conferencia; VI International Conference on Environmental, Industrial and Applied Microbiology - BioMicroWorld2015; 2015

http://dsrna2015.org/

Sewage contamination of water bodies poses a definite risk to human health via waterborne pathogens. Viruses, along with bacteria and protozoa in the intestine of humans and non-humans infected individuals are excreted in high concentration in the faeces and can enter the environmental waters at distinct locations. An approach has been to monitor for fecal indicator bacteria (FIB) include thermotolerant coliforms, E. coli and enterococci. The use of FIB as surrogates for human health risk is replete with assumptions, one of the most important of which is that FIB consistently covary with pathogen presence; however, FIB concentrations have not been well correlated with pathogens detection in many studies. In a bit to mitigate the risks of waterborne pathogens to human health by faecally contaminated recreational waters, monitoring, assessing and managing microbiological quality of surface waters is needed. The identification of fecal contamination sources in water using specific markers is a key step for good management and remediation protocols. The objective of the present research was to reach the best discriminating parameters of microbial water quality for surface waters which also inform about the animal specie source of fecal pollution.A total of 48 surface water samples were collected during the period January-December 2012, from the complex San Roque Dam and its two tributary rivers (named San Antonio and Cosquín), located at Córdoba Province, Argentina. The samples were analysed by traditional FIB (thermotolerant coliforms, E. coli, and enterococci) in concurrence with qualitative RTPCR virus genome detection (rotavirus group A, astrovirus, norovirus, poliomavirus JC and picobirnavirus) as well as viable human enterovirus, as an indicator of viable and infectious virus, after 100X virus concentration by polyethilenglycol method. It were selected 4 monitoring point: two central sites at the dam and in each one of the tributary mouth rivers. The study was conducted with a monthly sampling frequency. A linear regression test was used to analyze the relationship between the densities of fecal indicator bacteria. The 95% confidence intervals (CI) for viral proportion was estimated by Wilson score interval. Of the total samples analyzed (n=48) 10/48 (20.8%; 95%CI, 11.7-34.3), 8/48 (16.7%; 95%CI, 8.7-29.6) and 3/48 (6.3%; 95%CI 2.1-16.8) exceeded the fecal indicator bacteria level guide values established by international standards for secondary contact for recreational water for thermotolerant coliforms, E.coli and enterococcus respectively. Internal consistence analysis by means of Cronbach?s Alpha reveals the inter-relatedness of the items E. coli and thermotolerant coliforms (0.957). In addition, a lineal regression approach showed a positive correlation (R2=95.6) between these two bacterial indicator, been thermotolerant coliforms a fecal bacterial indicator slightly more sensitive than E. coli. The frequency of thermotolerant coliforms exceeding the adopted guidelines levels was significant higher in the mouths of the tributary rivers (8/10, 80%) as compared with the monitoring central and toma sites (2/10, 20%; p=0.01), all values detected during the summer months. Besides, overall viral frequency detection was 25/48 (52.1%, 95% CI, 38.3-65.5) for rotavirus, 39/48 (81,25%, 95%CI, 68.1-89.8) for picobirnavirus, 30/48 (62.5%, 95%CI, 48.4-74.8) for human enterovirus, 24/48 (50%, 95%CI,36.4-63.6) for astrovirus, 30/48 (62.5%, 95%CI, 48.4-74.8) for norovirus and 26/48 (54,2%, 95%CI, 40.3-67.4) for JC polyomavirus. The total water samples with values under the level guide of thermotolerant coliforms were positive for the detection of one or more of the viral groups analyzed, all through the year. Among the viral groups studied picobirnavirus and/or human enterovirus were detected in the 93.7% of the water samples studied, all through the year. Always, picobirnavirus and/or viable enterovirus detection mirrowed the presence of rotavirus and/or astrovirus and/or norovirus and/or JC polymavirus. The presence of viral genome as well as viable and infectious virus in areas where fecal contamination was not demonstrated by bacterial indicators suggests prolonged virus persistence in aquatic environments and emphasizes the enteric virus groups as the most reliable for microbial water quality monitoring. The joint detection of viable human enterovirus and PBV genome, could be used to provide evidence of human and animal fecal contamination in water surface all through the year as well as the potential presence of the main viruses responsible for human acute gastroenteritis.