Effects of the Antimicrobial Sulfamethoxazole on Groundwater Bacterial Enrichment

Abstract

The effects of "trace" (environmentally relevant) concentrations of the antimicrobial agent sulfamethoxazole (SMX) on the growth, nitrate reduction activity, and bacterial composition of an enrichment culture prepared with groundwater from a pristine zone of a sandy drinking-water aquifer on Cape Cod, MA, were assessed by laboratory incubations. When the enrichments were grown under heterotrophic denitrifying conditions and exposed to SMX, noticeable differences from the control (no SMX) were observed. Exposure to SMX in concentrations as low as 0.005 μM delayed the initiation of cell growth by up to 1 day and decreased nitrate reduction potential (total amount of nitrate reduced after 19 days) by 47% (p=0.02). Exposure to 1 μM SMX, a concentration below those prescribed for clinical applications but higher than concentrations typically detected in aqueous environments, resulted in additional inhibitions: reduced growth rates (p=5×10(-6)), lower nitrate reduction rate potentials (p=0.01), and decreased overall representation of 16S rRNA gene sequences belonging to the genus Pseudomonas. The reduced abundance of Pseudomonas sequences in the libraries was replaced by sequences representing the genus Variovorax. Results of these growth and nitrate reduction experiments collectively suggest that subtherapeutic concentrations of SMX altered the composition of the enriched nitrate-reducing microcosms and inhibited nitrate reduction capabilities.

Excretion masses and environmental occurrence of antibiotics in typical swine and dairy cattle farms in China

“…tetracyclines, fluoroquinolones and sulfonamides) could persist in the soils for a long time (Forster et al, 2009;Golet et al, 2003;Hamscher et al, 2002). Antibiotic residues in soil could be taken up by vegetables Hu et al, 2010), and affect soil microbial and enzyme activities (Liu et al, 2009;Underwood et al, 2011), thus resulting in negative impacts on the soil environment and human health.…”

“…Antibiotic residues in the environment can affect aquatic and terrestrial organisms (Costanzo et al, 2005;Kotzerke et al, 2011Kotzerke et al, , 2008Liu et al, 2009), alter microbial activity and community composition in groundwater (Underwood et al, 2011), and cause the development of antibiotic resistance by exerting the selective pressure on the microbial community (Pruden et al, 2006). However, most reported investigations focused more on tetracyclines, sulfonamides and fluoroquinolones in animal wastes in livestock farms due to available analytical methods, less on other classes of antibiotics such as bacitracin, leucomycin, lincomycin, florfenicol, ceftiofur and ionophores (Ben et al, 2008;Campagnolo et al, 2002;Chen et al, 2012aChen et al, , 2012bJacobsen and Halling-Sorensen, 2006;Karci and Balcioglu, 2009;Martínez-Carballo et al, 2007;Tagiri-Endo et al, 2009;Watanabe et al, 2010;Zhao et al, 2010).…”

Removal of antibiotics and antibiotic resistance genes from domestic sewage by constructed wetlands: Optimization of wetland substrates and hydraulic loading

“…After administration, antibiotic residues can be released into the receiving environments through discharge of the feces or urine, thus posing potential risks to human health and ecosystem (Costanzo et al, 2005;Kotzerke et al, 2008;Liu et al, 2009;Underwood et al, 2011). Use of antibiotics in humans and animals could also lead to development and spread of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the environment (Pruden et al, 2006;Tao et al, 2010;Su et al, 2012).…”

Occurrence and fate of eleven classes of antibiotics in two typical wastewater treatment plants in South China

“…Wide occurrence of antibiotics in the environment could affect aquatic and terrestrial organisms (Costanzo et al, 2005;Kotzerke et al, 2008;Liu et al, 2009), alter microbial activity and community composition (Underwood et al, 2011), and lead to prevalence of bacterial resistance to antibiotics (LaPara et al, 2011;Su et al, 2012;Tao et al, 2010). In order to reduce the negative impacts on the environment and human health, it is necessary to understand the input sources for various classes of antibiotics.…”