The treatment of wastewater containing pharmaceuticals in microcosm constructed wetlands: the occurrence of integrons (int1–2) and associated resistance genes (sul1–3, qacEΔ1)

Abstract

The aim of this study was to analyze the occurrence of sulfonamide resistance genes (sul1–3) and other genetic elements as antiseptic resistance gene (qacEΔ1) and class 1 and class 2 integrons (int1–2) in the upper layer of substrate and in the effluent of microcosm constructed wetlands (CWs) treating artificial wastewater containing diclofenac and sulfamethoxazole (SMX), which is a sulfonamide antibiotic. The bacteria in the substrate and in the effluents were equipped with the sul1–2, int1, and qacEΔ1 resistance determinants, which were introduced into the CW system during inoculation with activated sludge and with the soil attached to the rhizosphere of potted seedlings of Phalaris arundinacea ‘Picta’ roots (int1). By comparing the occurrence of the resistance determinants in the upper substrate layer and the effluent, it can be stated that they neither were lost nor emerged along the flow path. The implications of the presence of antibiotic resistance genes in the effluent may entail a risk of antibiotic resistance being spread in the receiving environment. Additionally, transformation products of SMX were determined. According to the obtained results, four (potential) SMX transformation products were identified. Two major metabolites of SMX, 2,3,5-trihydroxy-SMX and 3,5-dihydroxy-SMX, indicated that SMX may be partly oxidized during the treatment. The remaining two SMX transformation products (hydroxy-glutathionyl-SMX and glutathionyl-SMX) are conjugates with glutathione, which suggests the ability of CW bacterial community to degrade SMX and resist antimicrobial stress.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-017-9079-1) contains supplementary material, which is available to authorized users.

Identification of Selected Antibiotic Resistance Genes in Two Different Wastewater Treatment Plant Systems in Poland: A Preliminary Study

“…Environmental stressors such as antibiotics and heavy metals accumulated in surface soil could promote horizontal gene transfer between foreign and indigenous bacteria [ 38 ]. Other authors suggested [ 67 ] that the survival of rhizospheric bacteria of CWs can be also associated with their increased resistance to various environment stressors.…”

Molecular Methods as Potential Tools in Ecohydrological Studies on Emerging Contaminants in Freshwater Ecosystems

“…PCR Molecular techniques, such as PCR, can be used to evaluate the efficiency of constructed wetlands (CWs) for removal of particular CECs like ARGs. For example, Nowrotek et al [57] estimated the efficiency of downflow CW, planted with Phalaris arundinacea (read canary grass), for the removal of three ARGs encoding resistance to disinfectants: sul1-3, int2, qacE∆1. The presence of the selected genes was analyzed in: (1) rhizosphere soil of plant seedlings before transfer to the columns; (2) activated sludge that served as an inoculum; (3) tap water that was used to prepare artificially contaminated wastewater; (4) effluents; and (5) upper layer of substrate at different stages of the experiment.…”

Fate of Environmental Pollutants

“…Proliferation of ARGs during sequencing batch reactor (SBR) treatment was assessed by Nowrotek et al (2017).…”

“…One of the main pathways of ARBs and ARGs occurrences in the environment is via the release of wastewater effluent into water bodies (Nowrotek et al, 2017). In effluent samples taken from ten municipal WWTPs in China, higher abundance of sulfonamideresistant bacteria (SRB) than that of tetracycline-resistant bacteria (TRB) were recorded which was likely due to wider use of sulphonamide than tetracycline .…”

“…The presence of sulfanomide resistance genes (sul1-2), class 1 integrons (int1), and antiseptic resistance genes ( ) were detected in effluent of synthetic wastewater containing sulfamethoxazole and diclofenac treated by constructed wetlands (Nowrotek et al, 2017). Intergrons, e.g.…”