Location: Genetics and Sustainable Agriculture ResearchTitle: Removal of fecal indicator bacteria and antibiotic resistant genes in constructed wetlands
|LAMORI, JENNIFER - Tulane University|
|XUE, JIA - Tulane University|
|RACHMADI, ANDRI - Hokkaido University|
|LOPEZ, GERADRDO - University Of Arizona|
|KITAJIMA, MASAAKI - Hokkaido University|
|GERBA, CHARLES - University Of Arizona|
|PEPPER, IAN - University Of Arizona|
|SHERCHAN, SAMENDRA - Tulane University|
Submitted to: Journal of Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2019
Publication Date: 2/13/2019
Citation: Lamori, J.G., Xue, J., Rachmadi, A.T., Lopez, G., Kitajima, M., Gerba, C.P., Pepper, I.L., Brooks, J.P., Sherchan, S. 2019. Removal of fecal indicator bacteria and antibiotic resistant genes in constructed wetlands. Journal of Environmental Management. 26(10):10188-10197. https://doi.org/10.1007/s11356-019-04468-9.
Interpretive Summary: Discharge of municipal wastewater can be a costly process, but the use of constructed wetlands may help reduce pathogenic bacteria and antibiotic resistance in a sustainable fashion, allowing for a more natural approach to the process. In the current study, various fecal indicator bacteria, bacteria which indicate the presence of fecal contamination, also acting as indicators of pathogenic bacteria, were monitored in constructed wetlands. Additionally, antibiotic resistance genes were monitored using molecular methods. Cultivation-based methods determined that E. coli and Enterococcus were found occasionally in the wetland samples, but molecular methods, which are inherently more conservative, found these bacteria with more regularity. All water samples contained some type of antibiotic resistance gene or genes associated with resistance transfer, with genes associated with resistance to macrolide antibiotics (e.g. erythromycin) were found regularly. This indicates that constructed wetlands were not completely effective in reducing these key pathogen indicators or antibiotic resistance.
Technical Abstract: Wastewater discharge evidently increased bacterial diversity in the receiving waterbodies. The objective of this study was to evaluate the effectiveness of a constructed wetland in reducing fecal indicator bacteria and antibiotic resistant genes. We determined the prevalence and attenuation of fecal indicator bacteria including E. coli and Enterococcus, along with antibiotic resistance genes (ARGs), human-associated Bacteroidales (HF183) markers by quantitative polymerase chain reaction (qPCR) method. Three types of water samples from a constructed wetland (inlet, intermediate, and outlet) were collected once a month from May to December in 2013. The overall reduction of E. coli was 50.0% based on culture method. According to the qPCR result, the overall removal rate of E. coli was only 6.7%. Enterococcus were found in 62.5% (15/24) of the wetland samples. HF183 genetic marker was detected in all outlet water samples with concentration ranging from 1.8 to 4.22 log10 gene copies (GC)/100ml. Of the ARGs tested, erythromycin resistance genes (erm) (F) was detected in 79.2% (19/24) of the wetland samples. The class 1 integrons (intI1) was detected in all water samples with concentration ranging from 0.83 to 5.54 log10 GC/100ml. The overall removal rates of Enterococcus, HF183, intI1 and erm(F) were 84.0%, 66.6%, 67.2%, and 13.1%, respectively. The prevalence of FIB even after treatment suggests that there could be additional factors to resilience, such as ARGs that should be further investigated to understand completely.