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. 2019 Mar 15:656:495-502.
doi: 10.1016/j.scitotenv.2018.11.325. Epub 2018 Nov 22.

Viability-based quantification of antibiotic resistance genes and human fecal markers in wastewater effluent and receiving waters

Alessia Eramo  1 , William R Morales Medina  2 , Nicole L Fahrenfeld  3
Affiliations

Viability-based quantification of antibiotic resistance genes and human fecal markers in wastewater effluent and receiving waters

Alessia Eramo et al. Sci Total Environ. .

Abstract

Antibiotic resistance is a public health issue with links to environmental sources of antibiotic resistance genes (ARGs). ARGs from nonviable sources may pose a hazard given the potential for transformation whereas ARGs in viable sources may proliferate during host growth or conjugation. In this study, ARGs in the effluent from three municipal wastewater treatment plants (WWTPs) and the receiving surface waters were investigated using a viability-based qPCR technique (vPCR) with propidium monoazide (PMA). ARGs sul1, tet(G), and blaTEM, fecal indicator marker BacHum, and 16S rRNA gene copies/mL were found to be significantly lower in viable-cells than in total concentrations for WWTP effluent. Viable-cell and total gene copy concentrations were similar in downstream samples except for tet(G). Differences with respect to season in the prevalence of nonviable ARGs in surface water or WWTP effluent were not observed. The results of this study indicate that qPCR may overestimate viable-cell ARGs and fecal indicator genes in WWTP effluent but not necessarily in the surface water >1.8 km downstream.

Keywords: Antibiotic resistance genes; Chlorination; Propidium monoazide; Wastewater; vPCR.

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Figures

Figure 1
Figure 1
Concentrations of ARGs (a.) sul1, (b.) tet(G), and (c.) blaTEM, (d.) fecal indicator marker BacHum, and (e.) 16S rRNA present overall (total) and in viable cells only (viable) measured in effluent and downstream samples from wastewater treatment plant A, B, and C during summer and winter seasons. Boxes represent upper and lower quartiles, whiskers extend to high and low data points excluding outliers, and dots indicate outliers.
Figure 2
Figure 2
Ratios of viable-cell gene concentrations measured by vPCR to total gene concentrations measured by qPCR in effluent and downstream samples.
Figure 3
Figure 3
Concentrations of 16S rRNA in centrifuge-concentrated E. coli culture at exponential phase, river samples only (water pellet), centrifuge-concentrated river samples with a live cell culture spike (water pellet + live), and centrifuge-concentrated river samples with an inactivated (heat-treated) cell culture spike (water pellet + dead). Samples were analyzed by qPCR (0 µM PMA) and vPCR (50 or 100 µM PMA), which represent total and viable-cell concentrations, respectively.
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