Reclaimed water as a reservoir of antibiotic resistance genes: distribution system and irrigation implications

Abstract

Treated wastewater is increasingly being reused to achieve sustainable water management in arid regions. The objective of this study was to quantify the distribution of antibiotic resistance genes (ARGs) in recycled water, particularly after it has passed through the distribution system, and to consider point-of-use implications for soil irrigation. Three separate reclaimed wastewater distribution systems in the western U.S. were examined. Quantitative polymerase chain reaction (qPCR) was used to quantify ARGs corresponding to resistance to sulfonamides (sul1, sul2), macrolides (ermF), tetracycline [tet(A), tet(O)], glycopeptides (vanA), and methicillin (mecA), in addition to genes present in waterborne pathogens Legionella pneumophila (Lmip), Escherichia coli (gadAB), and Pseudomonas aeruginosa (ecfx, gyrB). In a parallel lab study, the effect of irrigating an agricultural soil with secondary, chlorinated, or dechlorinated wastewater effluent was examined in batch microcosms. A broader range of ARGs were detected after the reclaimed water passed through the distribution systems, highlighting the importance of considering bacterial re-growth and the overall water quality at the point of use (POU). Screening for pathogens with qPCR indicated presence of Lmip and gadAB genes, but not ecfx or gyrB. In the lab study, chlorination was observed to reduce 16S rRNA and sul2 gene copies in the wastewater effluent, while dechlorination had no apparent effect. ARGs levels did not change with time in soil slurries incubated after a single irrigation event with any of the effluents. However, when irrigated repeatedly with secondary wastewater effluent (not chlorinated or dechlorinated), elevated levels of sul1 and sul2 were observed. This study suggests that reclaimed water may be an important reservoir of ARGs, especially at the POU, and that attention should be directed toward the fate of ARGs in irrigation water and the implications for human health.

High Throughput Profiling of Antibiotic Resistance Genes in Urban Park Soils with Reclaimed Water Irrigation

“…11,20,21 Furthermore, the propagation and dissemination of ARGs could be facilitated via horizontal gene transfer mechanisms. 22 Reclaimed water is evidently a reservoir of ARGs 23 and, therefore, the effect of irrigation with reclaimed water on ARGs needs definition.…”

Impacts of reclaimed water irrigation on soil antibiotic resistome in urban parks of Victoria, Australia

“…The continuous release of ARB, ARGs and antibiotic residues from effluents of WWTPs could cause the dissemination of ARGs in environments receiving these effluents (Czekalski et al, 2014;Wang et al, 2014b;Rodriguez-Mozaz et al, 2015), which has become a global concern (Berendonk et al, 2015). Although reclaimed water has been recognized as an important reservoir of ARB and ARGs (Fahrenfeld et al, 2013), only a limited number of studies have assessed the fate of reclaimed waterderived ARGs in downstream environments (Negreanu et al, 2012;Fahrenfeld et al, 2013), and people are not aware of the potential health risks they are facing. To date, impacts of treated wastewater on antibiotic resistance have been reported in rivers (LaPara et al, 2011), agricultural soils (McLain andWilliams, 2012;Negreanu et al, 2012;Fahrenfeld et al, 2013;Chen et al, 2014) and sediments (Czekalski et al, 2014), but only a few studies focused on the occurrence and prevalence of ARGs in urban park soils irrigated by reclaimed water (Wang et al, 2014a(Wang et al, , 2014b.…”

“…Although reclaimed water has been recognized as an important reservoir of ARB and ARGs (Fahrenfeld et al, 2013), only a limited number of studies have assessed the fate of reclaimed waterderived ARGs in downstream environments (Negreanu et al, 2012;Fahrenfeld et al, 2013), and people are not aware of the potential health risks they are facing. To date, impacts of treated wastewater on antibiotic resistance have been reported in rivers (LaPara et al, 2011), agricultural soils (McLain andWilliams, 2012;Negreanu et al, 2012;Fahrenfeld et al, 2013;Chen et al, 2014) and sediments (Czekalski et al, 2014), but only a few studies focused on the occurrence and prevalence of ARGs in urban park soils irrigated by reclaimed water (Wang et al, 2014a(Wang et al, , 2014b. Public urban parks play a vital role in the social life of human beings, and provide a potentially important pathway for the spread of ARGs from soil to human pathogens.…”

“…Due to the intensive anthropogenic activities such as aquaculture, land application of manure and biosolids, and large inputs of ARGs from the reuse of reclaimed water (LaPara et al, 2011;Cytryn, 2013;Zhu et al, 2013;Wang et al, 2014a), soil has been recognized as the largest environmental reservoir of antibiotic resistance (Nesme et al, 2014). Reclaimed water irrigation (RWI) is a practical solution for overcoming water resource shortage, and has been widely utilized in arid and semi-arid regions of the world (Fahrenfeld et al, 2013;Berendonk et al, 2015). Given the increasingly exacerbated water scarcity owing to urbanization, population growth and less available freshwater, it is anticipated that RWI will likely be more widely applied in the future (Wang et al, 2014a).…”

Mechanisms of antibiotic resistance

“…The occurrence of antibiotics resistance genes in finfish aquaculture environments is further discussed by Miranda et al (2013). The presence of antibiotic resistance genes in the aquatic environment is also demonstrated by Fahrenfeld et al (2013) and Suzuki et al (2013). To address the key issue concerning the role of environmental resistance gene reservoir in the emergence of clinically important resistant pathogens, Perry and Wright (2013) reviewed recent works suggesting genetic exchange between the environmental and clinical resistomes.…”