Microbiological hazard identification in river waters used for recreational activities.

Pathogenic bacteria, viruses, and parasites can cause waterborne disease outbreaks. The study of coastal water quality contributes to identifying potential risks to human health and to improving water management practices. The Río de la Plata River, a wide estuary in South America, is used for recreational activities, as a water source for consumption and as a site for sewage discharges. In the present study, as the first step of a quantitative microbial risk assessment of the coastal water quality of this river, a descriptive study was performed to identify the microbial pathogens prevalent in its waters and in the sewage discharged into the river. Two sites, representing two different potential risk scenarios, were chosen: a heavily polluted beach and an apparently safe beach. Conductivity and fecal contamination indicators including enterococci, Escherichia coli, F + RNA bacteriophages, and human polyomaviruses showed high levels. Regarding enterococci, differences between sites were significant (p-values <0.001). 93.3% and 56.5% of the apparently safe beach exceeded the recreational water limits for E. coli and enterococci. Regarding pathogens, diarrheagenic E. coli, Salmonella, and noroviruses were detected with different frequencies between sites. The parasites Cryptosporidium spp. and Giardia duodenalis were frequently detected in both sites. The results regarding viral, bacterial, and parasitic pathogens, even without correlation with conventional indicators, showed the importance of monitoring a variety of microorganisms to determine water quality more reliably and accurately, and to facilitate further studies of health risk assessment. The taxonomic description of microbial pathogens in river waters allow identifying the microorganisms that infect the population living on its shores but also pathogens not previously reported by the clinical surveillance system.

[Human parasites in surface water used for recreation in Salta, Argentina]. / Parásitos humanos en aguas superficiales de uso recreativo en Salta, Argentina.

Waterborne diseases can have different origins, micro-organisms such as bacteria and parasites being the most important ones. In this study, two recreational aquatic environments were studied in the province of Salta, Argentina. Water samples collected from three different locations, two from a creek and one from the outlet of a thermal complex, were monitored at four time points. Physicochemical and microbiological characterization of each point was conducted, as well as a search for parasites and amebae. Parasites were identified through optical microscopy observations and free-living amebae (FLA) were isolated by spiking in Petri dishes followed by subsequent molecular identification. Water samples from the outlet of the thermal complex showed different physicochemical characteristics from those of the creek. Bacterial indicators of contamination were detected at all points; however, the creek water had a significantly higher concentration of Pseudomonas sp. Sporadically, creek samples exhibited Ascaris spp. eggs, Giardia sp. cysts, and ancylostomid eggs. The presence of FLA was observed in all samples, 15 of which were isolated and identified as Acanthamoeba sp., mostly belonging to the T4 genotype. Parasite surveillance in recreational aquatic environments is an important complement to traditional microbial indicators for assessing water quality. The identified parasites represent a potential health risk for people using these environments.

Sewershed surveillance as a tool for smart management of a pandemic in threshold countries. Case study: Tracking SARS-CoV-2 during COVID-19 pandemic in a major urban metropolis in northwestern Argentina.

Wastewater-based epidemiology is an economical and effective tool for monitoring the COVID-19 pandemic. In this study we proposed sampling campaigns that addressed spatial-temporal trends within a metropolitan area. This is a local study of detection and quantification of SARS-CoV-2 in wastewater during the onset, rise, and decline of COVID-19 cases in Salta city (Argentina) over the course of a twenty-one-week period (13 Aug to 30 Dec) in 2020. Wastewater samples were gathered from 13 sewer manholes specific to each sewershed catchment, prior to convergence or mixing with other sewer lines, resulting in samples specific to individual catchments with defined areas. The 13 sewershed catchments selected comprise 118,832 connections to the network throughout the city, representing 84.7 % (534,747 individuals) of the total population. The number of COVID19-related exposure and symptoms cases in each area were registered using an application developed for smartphones by the provincial government. Geographical coordinates provided by the devices were recorded, and consequently, it was possible to geolocalise all app-cases and track them down to which of the 13 sampling catchments belonged. RNA fragments of SARS-CoV-2 were detected in every site since the beginning of the monitoring, anticipating viral circulation in the population. Over the course of the 21-week study, the concentrations of SARS-CoV-2 ranged between 1.77 × 104 and 4.35 × 107 genome copies/L. There was a correspondence with the highest viral load in wastewater and the peak number of cases reported by the app for each catchment. The associations were evaluated with correlation analysis. The viral loads of SARS-CoV-2 in wastewater were a feasible means to describe the trends of COVID-19 infections. Surveillance at sewershed scale, provided reliable and strategic information that could be used by local health stakeholders to manage the COVID-19 pandemic.

Acanthamoeba and a bacterial endocytobiont isolated from recreational freshwaters.

The quality of many freshwater environments is impacted by human activities, so that many rivers may represent a vehicle for the transmission of health-related microorganisms. This work aimed to isolate and identify genetically free-living amoeba (FLA) of the genus Acanthamoeba from a recreational river in Salta, Argentina, and isolate, if possible, an endocytobiont. Sampling took place at four points (P1-P4) throughout the river in the winter and the summer seasons. Free-living amoebae and Acanthamoeba were recovered from 20-L water concentrated through an ultrafiltration system. Isolation was performed in agar plates, confirmation of Acanthamoeba genus by PCR, and fellow identification and classification based on their sequence analyses. High concentrations of indicator bacteria were found especially in P2, which is intensively used for recreation. Out of a total of 29 FLA isolations, 9 were identified as Acanthamoeba genotype T4 subtype A, the most frequent genotype found in nature and associated with causing human disease. From an axenic culture of Acanthamoeba spp. (KY751412), a bacterial endocytobiont was isolated, and identified as Stenotrophomonas maltophilia. The endocytobiont showed resistance and intermediate resistance to a wide range of widely used antibiotics. Results were in concordance with the cosmopolitan behavior of Acanthamoeba, and showed the importance of studying this group of amoebae and related microorganisms in recreational environments.

Tracking SARS-CoV-2 in rivers as a tool for epidemiological surveillance.

The aim of this work was to evaluate if rivers could be used for SARS-CoV-2 surveillance. Five sampling points from three rivers (AR-1 and AR-2 in Arenales River, MR-1 and MR-2 in Mojotoro River, and CR in La Caldera River) from Salta (Argentina), two of them receiving discharges from wastewater plants (WWTP), were monitored from July to December 2020. Fifteen water samples from each point (75 in total) were collected and characterized physico-chemically and microbiologically and SARS-CoV-2 was quantified by RT-qPCR. Also, two targets linked to human contributions, human polyomavirus (HPyV) and RNase P, were quantified and used to normalize SARS-CoV-2 concentration, which was compared to reported COVID-19 cases. Statistical analyses allowed us to verify the correlation between SARS-CoV-2 and the concentration of fecal indicator bacteria (FIB), as well as to find similarities and differences between sampling points. La Caldera River showed the best water quality; FIBs were within acceptable limits for recreational activities. Mojotoro River's water quality was not affected by the northern WWTP of the city. Instead, Arenales River presented the poorest water quality; at AR-2 was negatively affected by the discharges of the southern WWTP, which contributed to significant increase of fecal contamination. SARS-CoV-2 was found in about half of samples in low concentrations in La Caldera and Mojotoro Rivers, while it was high and persistent in Arenales River. No human tracers were detected in CR, only HPyV was found in MR-1, MR-2 and AR-1, and both were quantified in AR-2. The experimental and normalized viral concentrations strongly correlated with reported COVID-19 cases; thus, Arenales River at AR-2 reflected the epidemiological situation of the city. This is the first study showing the dynamic of SARS-CoV-2 concentration in an urban river highly impacted by wastewater and proved that can be used for SARS-CoV-2 surveillance to support health authorities.