Antibiotic resistance response of activated sludge to sulfamethoxazole

Antibiotic resistance response of activated sludge to sulfamethoxazole: insights from the intracellular and extracellular DNA fractions

Martinez Quintela, M. (TU Delft BT/Environmental Biotechnology; Universidade de Santiago de Compostela)
Calderon Franco, D. (TU Delft BT/Environmental Biotechnology)
van Loosdrecht, Mark C.M. (TU Delft BT/Environmental Biotechnology)
Suárez, S. (Universidade de Santiago de Compostela)
Omil, F. (Universidade de Santiago de Compostela)
Weissbrodt, D.G. (TU Delft BT/Environmental Biotechnology; Norwegian University of Science and Technology (NTNU))

2024

In activated sludge, the antibiotic resistance genes (ARGs) can be present either in the intracellular (iDNA) or extracellular DNA fraction (exDNA). Recent advances in the exDNA extraction methodology allow a better profiling of the pool of ARGs. However, little is known about how stress conditions modify the distribution of ARGs between both DNA fractions. Here, we performed two batch tests for analyzing the effects of two different stress conditions, namely nutrient starvation and high concentrations of sulfamethoxazole (1, 10 and 150 mg L⁻¹) in activated sludge. We tracked by qPCR the resulting relative abundances of four target genes, namely the universal 16S rRNA gene, the class 1 integron-integrase gene intI1, and the sulfonamide resistance genes sul1 and sul2 in both the iDNA and exDNA fractions. In the exDNA pool, unlike starvation, which provoked a decrease of 1-2 log₁₀ [copies] per ng DNA in the concentration of sul1 and intI1, the presence of sulfamethoxazole did not influence the abundances of sul1 and sul2. However, high concentrations of sulfamethoxazole (150 mg L⁻¹) selected for microorganisms harboring sul1 and, more remarkably, sul2 genes in their iDNA during their exponential growth phase. The abundances of intI1 and sul1 were positively correlated in the exDNA fraction (r > 0.7), whereas no significant correlation (p < 0.05) between the abundance of these two genes was found in the iDNA fraction of the sludge. High SMX concentrations influenced the abundance of ARGs in the iDNA; their abundance in the exDNA was influenced by nutrient limitations. Further studies should consider the profiling of exDNA fractions because of the relationship between ARGs and mobile genetic elements. Besides, the surveillance of antimicrobial resistance is encouraged in wastewater treatment plants facing high antibiotic concentrations.

http://resolver.tudelft.nl/uuid:d6b7fa8d-b438-4fa7-90d9-cf3308c3ad2b

https://doi.org/10.1039/d3ew00591g

2024-11-01

2053-1400

Environmental Science: Water Research & Technology

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2024 M. Martinez Quintela, D. Calderon Franco, Mark C.M. van Loosdrecht, S. Suárez, F. Omil, D.G. Weissbrodt