Combined membrane filtration and 265 nm UV irradiation for effective removal of cell free antibiotic resistance genes from feed water and concentrate

Pawel Krzeminski,Edward Feys,Marc Anglès D'Auriac,Aina Charlotte Wennberg,Muhammad Umar,Carsten Ulrich Schwermer,Wolfgang Uhl

doi:10.1016/j.memsci.2019.117676

Abstract

The removal of cell free DNA (plasmids) carrying antibiotic resistance genes (ARGs) was investigated at bench-scale using ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes commonly applied in water reuse applications. The removal of the plasmid spiked to ultrapure water was determined using a direct qPCR method. More than 99% plasmid removal was achieved by membranes with 1 kDa molecular weight cut off (MWCO). Membranes with lower MWCO showed complete removal under the specific experimental conditions, reaching a maximum log reduction value above 6.6. The concentrate from membrane filtration was further subjected to UV-LED irradiation at 265 nm. The required fluence for 1 log damage was 73 mJ/cm2 for the 267 target bp segment and 23 mJ/cm2 for the 601 target bp segment, respectively. With these two DNA segments, the inactivation rate per segment length was higher for the larger segment, in accordance with a higher pyrimidine and TT content, compared with the smaller fragment. Target DNA was not detectable anymore when using 100 and 300 mJ/cm2 for the 601 and 267 bp segments respectively. The results indicate that membrane filtration, combined with UV-LED treatment of the concentrate, can be an effective measure to remove and inactivate ARGs from water to prevent their release to the environment.

Highlights

IntroductionWidespread use and misuse of antimicrobial agents (antibiotics, antifungals, antivirals, antiparasitics) contribute to the emergence and spread of antimicrobial resistance (AMR) in soil, drinking water, wastewater, fresh and marine waters, and in wildlife [1,2,3,4,5]
Widespread use and misuse of antimicrobial agents contribute to the emergence and spread of antimicrobial resistance (AMR) in soil, drinking water, wastewater, fresh and marine waters, and in wildlife [1,2,3,4,5]
The challenge feed water used for the membrane filtration experi ments was composed of ultrapure or tap water spiked with E. coli cell free DNA, containing the plasmid pCR®II-TOPO (Invitrogen, Life Technologies, Thermo Fisher Scientific Inc., Waltham, MA, USA) which has genes coding for resistance against kanamycin and ampicillin

Summary

Introduction

Widespread use and misuse of antimicrobial agents (antibiotics, antifungals, antivirals, antiparasitics) contribute to the emergence and spread of antimicrobial resistance (AMR) in soil, drinking water, wastewater, fresh and marine waters, and in wildlife [1,2,3,4,5]. AMR is a natural phenomenon, anthropogenic influence may lead to increased AMR occurrence in these compartments through different routes [6,7] Among these routes, treated wastewater and sludge from wastewater treatment plants (WWTPs), animal manure from agricul ture, and overuse of antibiotics in aquaculture, are the major pathways of AMR spread [8]. Global spreading of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the environment may negatively affect the health of humans and animals. Considering persistence of the cell free DNA in water and soil [18,20], ARB may re-emerge and antibiotic resistance prolif erate in the environment. It is necessary to focus on DNA monitoring and DNA inactivation, i.e., preventing functional activity of genes, in water treatment systems when seeking to mitigate antibiotic resistance

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