Citation:

Tiwari, A., V. Gomez-Alvarez, S. Siponen, A. Sarekoski, A. Hokajärvi, A. Kauppinen, E. Torvinen, I. Miettinen, AND T. Pitkänen. Bacterial Genes Encoding Resistance against Antibiotics and Metals in Well-Maintained Drinking Water Distribution Systems in Finland. Frontiers in Microbiology. Frontiers, Lausanne, Switzerland, 12:803094, (2022). https://doi.org/10.3389/fmicb.2021.803094

Impact/Purpose:

While disinfection strategies aim to mitigate the presence of microbes in drinking water distribution systems (DWDS), they do not completely eradicate their growth; therefore, a better understanding of the DWDS microbiome is needed to develop microbial control strategies. The information generated in this study improves our understanding of the drinking water ecosystem, particularly the potential sources of adverse exposure (unintended consequences of disinfectant switching practices) and how these sources may be monitored to ensure public and ecosystem health.

Description:

Co-occurrence of antibiotic resistance genes (ARG) and metal resistance genes (MRG) information among bacterial communities in drinking water distribution systems (DWDS) with different raw water sources and treatment methods are scarce. This study characterized the resistome (ARG and MRG) in five well-maintained DWDS in Finland. Two of the waterworks used artificially recharged groundwater (ARGW) as source and the finished water was treated with no disinfection. Three waterworks (two surface and one groundwater source) used UV light and chlorine during the treatment process. Ten bulk water samples (two from each DWDS) were collected, and environmental DNA was extracted and sequenced on a high-throughput shotgun metagenomic sequencing platform. A total of 430 ARGs were characterized among all samples with the highest diversity of ARGs identified from samples collected from non-disinfected DWDS. Furthermore, non-disinfected DWDS contained the highest diversity of bacterial communities. However, samples from DWDS using disinfectants contained over two times higher ratio of ARG reads to 16S rRNA-gene reads, and most of the genes were associated with MRG (mercury and arsenic resistant). The number and types of multidrug, bacitracin, beta-lactamase, aminoglycoside resistance, and mercury resistance genes increased in waterworks treating surface water with disinfection. The findings of this study deepen a comprehensive understanding of ARGs and MRGs in DWDSs. The exposure of antibiotic-resistant bacteria (ARB) via drinking water to people is a serious concern and thus, more systematic investigation is needed to decipher the magnitude of human health risk.

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