Molecular Analyses of Fecal Bacteria and Hydrodynamic Modeling for Microbial Risk Assessment of a Drinking Water Source
Abstract
:1. Introduction
2. Materials and Methods
2.1. Case Study Area
2.2. Collection of Surface Water
2.3. DNA Extraction
2.4. Quantitative PCR
2.5. Hydrodynamic Modeling
2.6. Quantitative Microbial Risk Assessment
2.7. Statistical Analyses
3. Results
3.1. Detection of ssrA Positive Bacteria by Real-Time PCR
3.2. Comparison of ssrA Data with Routine Culture Assays
3.3. Detection of Pathogens by Real-Time PCR
3.4. Hydrodynamic Modeling of ssrA Concentrations
3.5. QMRA Analyses
4. Discussion
5. Conclusions
- Molecular methods indicated presence of enterobacteria detected by the ssrA primers and of Salmonella detected by invA primers in the water samples at distinct times. The samples collected during the colder period often had concentrations of ssrA below the detection limit, while samples collected in April, July, August, and September 2015 were more often positive.
- The ssrA primers detect genes of the genera Escherichia, Klebsiella, Citrobacter, and Enterobacter that constitute the defined group of coliforms. However, the molecular methods will also detect genetically closely related genera as well as potentially amplify DNA from bacteria not able to grow on plates. The direct comparison between coliforms or E. coli measured using culture methods and the ssrA DNA copies measured using real-time PCR analysis is not straightforward and further investigations are needed.
- Hydrodynamic modeling showed that ssrA contribution from tributaries to the concentrations at the water intake was the highest for Björkaån followed by Torpsbäcken, Borstbäcken, and wastewater from on-site sewers.
- Given the current processes in the drinking water treatment plant, the quantitative microbial risk assessment showed that an acceptable risk level can be achieved if <10 Salmonella per 100 mL is observed in the water intake from the lake. If UV-disinfection is installed, an acceptable risk level is achieved if <5 × 106 Salmonella per 100 mL is observed.
Supplementary Materials
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Gene | Forward Primer 3′–5′ | Reverse Primer 3′–5′ | Size | Tm | Reference |
---|---|---|---|---|---|
ssrA | CGAATCAGGCTAGTCTGGTAGTG | GCGTCCGAAATTCCTACATC | 102 | 81.4 | This study |
invA | TCGTCATTCCATTACCTACC | AAACGTTGAAAAACTGAGGA | 119 | 78.5 | Hoorfar, et al. [30] |
cadF | TCAAGTCTTAAAGCCAAAGAATC | AGCAGGTGGAGGATATGAGG | 119 | 77.1 | Sjoling, et al. [31] |
EHEC | TATCAGCACCAAAGAGCGGGAACA | CCCTTATGAAGAGCCAGTACTGAA | 99 | 78.9 | Luedtke, et al. [32] |
Target Gene | ssrA (coliforms) | |
---|---|---|
Sampling Points b | Warm Period: Positive (tot.) | Cold Period: Positive (tot.) |
Boreholes 1a | 22 (50) | 10 (38) |
Intake 1b | 13 (50) | 2 (41) |
Wastewater 2a | 30 (42) | 24 (40) |
Björkaån 2b | 12 (46) | 5 (44) |
Torpsbäcken 3 | 20 (49) | 5 (38) |
Borstbäcken 4 | 16 (50) | 5 (34) |
Groundwater 6 | 7 (39) | 4 (38) |
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Chuquimia, O.D.; Bergion, V.; Guzman-Otazo, J.; Sörén, K.; Rosén, L.; Pettersson, T.J.R.; Sokolova, E.; Sjöling, Å. Molecular Analyses of Fecal Bacteria and Hydrodynamic Modeling for Microbial Risk Assessment of a Drinking Water Source. Water 2020, 12, 3. https://doi.org/10.3390/w12010003
Chuquimia OD, Bergion V, Guzman-Otazo J, Sörén K, Rosén L, Pettersson TJR, Sokolova E, Sjöling Å. Molecular Analyses of Fecal Bacteria and Hydrodynamic Modeling for Microbial Risk Assessment of a Drinking Water Source. Water. 2020; 12(1):3. https://doi.org/10.3390/w12010003
Chicago/Turabian StyleChuquimia, Olga D., Viktor Bergion, Jessica Guzman-Otazo, Kaisa Sörén, Lars Rosén, Thomas J. R. Pettersson, Ekaterina Sokolova, and Åsa Sjöling. 2020. "Molecular Analyses of Fecal Bacteria and Hydrodynamic Modeling for Microbial Risk Assessment of a Drinking Water Source" Water 12, no. 1: 3. https://doi.org/10.3390/w12010003
APA StyleChuquimia, O. D., Bergion, V., Guzman-Otazo, J., Sörén, K., Rosén, L., Pettersson, T. J. R., Sokolova, E., & Sjöling, Å. (2020). Molecular Analyses of Fecal Bacteria and Hydrodynamic Modeling for Microbial Risk Assessment of a Drinking Water Source. Water, 12(1), 3. https://doi.org/10.3390/w12010003