Effects of full-scale advanced water treatment on antibiotic resistance genes in the Yangtze Delta area in China

Abstract

As emerging microbial contaminants, antibiotic resistance genes (ARGs) are widespread in the aquatic environment, including source water, which might enter water supply systems and endanger public health by enhancing the resistance of opportunistic pathogens to some antibiotics. In the present study, we investigated how water treatments affect the levels of ARGs in a full-scale drinking water treatment plant for one year using real-time PCR. The 16s rRNA gene and eleven ARG families, including tetA, tetG, aacC1, strA, ermB, cmlA5, vanA, dfrA1, sulII, blaTEM-1 and blaoxa-1, in source water and the outlet of each treatment and tap water were monitored. The results showed that nine ARG families were detected at relatively high levels, for example, the sulII gene was detected at ∼10(4) copies mL(-1) compared with 10(5) copies mL(-1) in finished water and tap water in July, whose relative concentrations were consistently high. Treatments for the reduction of the absolute concentrations of ARGs included sand filtration, coagulation/sedimentation and two-stage O3-BAC filtration, while distribution could increase ARGs an average of 0.50 log.

The occurrence of antibiotic resistance genes in tap water – a review

“…As a result, from 112 to 122 genes were found in tap water samples, depicting the diversity of ARGs in this medium [17]. The elevated level of ARGs in tap water, in comparison to treated water, was confirmed also by Zhang et al [51].…”

“…In general, the DNA obtained by commercial kits was pure enough to perform PCR assay (the minimum A260/A280 ratios was 1.40) and solutions obtained by phenol/chloroform methods required further purification steps in some cases, what could hinder PCR investigations [55]. The alternative solution was implemented by Zhang et al, who combined the application of the commercial kit with further phenol-ethanol methods [51].…”

“…According to the literature review, the volumes of fresh water and tap water used in DNA extraction procedures varied widely: from 15 L [49], through 10÷15 L depending on the sample contamination and possible clogging of membrane [51], 4 L [57], 2÷1 L [58][59][60], 1.5 L [61] to 500 ml [14] or 450 mL [42], depending on the sample origin. However, drinking water samples obtained by other researchers could have been affected by the biofilm dwelling in the taps.…”

“…Technologies presently applied in water treatment plants do not provide the sufficient ARGs removing levels [11,16,51,57]. The proposed improvements may be the increase in dosages of chlorine and the intensity of UV irradiation or sequential UV/chlorination [9], but these solutions generate high costs.…”

Bacteremia in critical care units at Bugando Medical Centre, Mwanza, Tanzania: the role of colonization and contaminated cots and mothers’ hands in cross-transmission of multidrug resistant Gram-negative bacteria

“…Therefore, this study found that, domestic use of tap water only as pre-admission history is protective factor (p = 0.040) for bacteremia. Treatment of water for domestic use by sand filtrations at water treatment plant in Mwanza [38], may have been played an effective role of reducing the absolute concentrations of MDR-bacteria and antibiotic resistance genes (ARGs) from contaminated source [39] as reported by Zhang et al, 2016 [40]. Thus, admitted neonates with parents' domestic use of water from open sources such as dams and lake, should be screened for possibilities of bacteremia due to GNB.…”