Abstract
Fecal pollution of surface water may introduce bacteria and bacteriophages harboring antibiotic resistance genes (ARGs) into the aquatic environment. Watercourses discharging into the marine environment, especially close to designated bathing waters, may expose recreational users to fecal pollution and therefore may increase the likelihood that they will be exposed to ARGs. This study compares the bacterial and bacteriophage ARG profiles of two rivers (River Tolka and Liffey) and two small urban streams (Elm Park and Trimleston Streams) that discharge close to two marine bathing waters in Dublin Bay. Despite the potential differences in pollution pressures experienced by these waterways, microbial source tracking analysis showed that the main source of pollution in both rivers and streams in the urban environment is human contamination. All ARGs included in this study, blaTEM, blaSHV, qnrS, and sul1, were present in all four waterways in both the bacterial and bacteriophage fractions, displaying a similar ARG profile. We show that nearshore marine bathing waters are strongly influenced by urban rivers and streams discharging into these, since they shared a similar ARG profile. In comparison to rivers and streams, the levels of bacterial ARGs were significantly reduced in the marine environment. In contrast, the bacteriophage ARG levels in freshwater and the marine were not significantly different. Nearshore marine bathing waters could therefore be a potential reservoir of bacteriophages carrying ARGs. In addition to being considered potential additional fecal indicators organism, bacteriophages may also be viewed as indicators of the spread of antimicrobial resistance.
Highlights
Microbial antibiotic resistance is a severe threat to public health, resulting in failure to treat a range of infections, in extended hospital treatment and in increased healthcare costs (Stewardson et al, 2016; Cassini et al, 2019; Roope et al, 2019; Jit et al, 2020)
We show that the antibiotic resistance genes (ARGs) profiles of these streams and rivers in an urban environment are highly similar and have a strong impact on nearshore marine bathing waters
The rivers Liffey and Tolka rise outside Dublin and flow through an agricultural area before entering the city and discharging into Dublin Bay
Summary
Microbial antibiotic resistance is a severe threat to public health, resulting in failure to treat a range of infections, in extended hospital treatment and in increased healthcare costs (Stewardson et al, 2016; Cassini et al, 2019; Roope et al, 2019; Jit et al, 2020). Aquatic Bacterial and Bacteriophage ARGs recently, the importance of the environment as a major contributor to the spread of antimicrobial resistance in the human and animal population has become increasingly clear (Allcock et al, 2017; Leonard et al, 2018; Hernando-Amado et al, 2020). Successful management strategies and policies to combat the increase in antimicrobial resistance will have to be based on a One Health approach, which recognizes the connectivity between animal, human, and environmental health (Hernando-Amado et al, 2019; Van Bruggen et al, 2019). Transduction by bacteriophages is an important mechanism in spreading ARGs within a microbial population (Muniesa et al, 2013b; Balcazar, 2014; Brown-Jaque et al, 2015; Balcázar, 2018; Maganha De et al, 2021). The importance of bacteriophages in spreading ARGs and virulence genes, was recently underscored by the discovery of lateral transduction, which is the basis of genomic hypermobility (Chen et al, 2018; Chiang et al, 2019)
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