Yi Luo

The occurrence of antibiotics and antibiotic resistance genes (ARGs) was quantified in water and sediment samples collected from a 72-km stretch of the Haihe River, China. Sulfachlororyridazine was detected in all swine farm and fishpond samples, which suggests its potential usefulness to indicate livestock source pollution in the Haihe River basin. River flow rate exerted the most significant effect on the first-order attenuation coefficient (K) for sulfonamides, quinolones and macrolides, with higher flow rate resulting in higher K probably due to dilution. For tetracyclines, sediment total organic matter and cation exchange capacity exerted a greater impact on K than flow rate, indicating that adsorption to sediments plays an important role in attenuating tetracyclines migration. This is the first regional study to report the presence of sul1 and sul2 genes as the predominant ARGs in regions where multiple antibiotic residues are present, and to provide direct field evidence of the selective pressure of antibiotic residues on the associated ARGs. (ES&T, 2010, 2011)

The New Delhi metallo-β-lactamase (NDM-1) increases bacterial resistance to a broad range of antibiotics, and bacteria that produce it can cause infections that are very difficult to treat, thus posing great risks to human health.This paper addresses the occurrence of NDM-1 genes though different processes in wastewater treatment plants (WWTPs). NDM-1 genes prevailed through several treatment units (including disinfection by chlorination) in two WWTPs in Northern China. Significant NDM-1 gene levels were present in the effluent discharged from both WWTPs. This is the first report of the occurrence, persistence and fate of NDM-1 genes through different processes in wastewater treatment plants (WWTPs). The discharge of NDM-1 genes in the effluent plus dewatered waste sludge from WWTPs underscores the need to better understand and mitigate their proliferation and propagation from WWTPs. (ES&T Lett, 2014).

  The emergence and spread of NDM-1 (New Delhi metallo-β-lactamase-1) is of a great concern to public health. Based on our previous study which reported the occurrence and persistence of NDM-1 genes through various processes in wastewater treatment plants, the blaNDM-1 gene and its host bacteria were investigated to study the occurrence and fate of blaNDM-1 genes in a receiving river following WWTP discharges.The quantification of blaNDM-1 genes and blaNDM-1 sequencing analysis of representative strains demonstrated that the occurrence of blaNDM-1 genes in receiving river is derived from the WWTP.The propagation of NDM-1 genes from WWTP effluent into receiving river underscores the needs not only to mitigate their proliferation from WWTPs, but also pay more attention to the pathway of their transportation to the receiving environment so as to alleviate their dissemination worldwide. (ES&T Lett, 2016)

      The propagation of antibiotic resistance genes (ARGs) represents a global threat to both human health and food security. Assessment of ARG reservoirs and persistence is therefore critical for devising and evaluating strategies to mitigate ARG propagation.This study developed a novel, internal standard method to extract extracellular DNA (eDNA) and intracellular DNA (iDNA) from water and sediments, and applied it to determine the partitioning of ARGs in the Haihe River basin in China, which drains an area of intensive antibiotic use.Overall, this study shows that extracellular DNA in sediment is a major ARG reservoir that could facilitate antibiotic resistance propagation. (ES&T, 2014)

      The propagation of antibiotic resistance genes (ARGs) is an emerging health concern worldwide. Thus, it is important to understand and mitigate their occurrence in different systems. In this study, 30 ARGs that confer resistance to tetracyclines, sulfonamides, quinolones or macrolides were detected in two activated sludge wastewater treatment plants in northern China. We found that Bacteria harboring ARGs persisted through all treatment units, and survived disinfection by chlorination in greater percentages than total Bacteria.Twelve ARGs (tetA, tetB, tetE, tetG, tetH, tetS, tetT, tetX, sul1, sul2, qnrB, ermC) were discharged through the dewatered sludge and plant effluent at higher rates than influent values, indicating overall proliferation of resistant bacteria.Significant antibiotic concentrations (2% to 50% of raw influent concentrations) remained throughout all treatment units. This apparently contributed selective pressure for ARG replication since the relative abundance of resistant bacteria was significantly correlated to the corresponding effluent antibiotic concentrations.Similarly, the concentrations of various heavy metals were also correlated to the enrichment of some ARGs.Thus, curtailing the release of antibiotics and heavy metals to sewage systems may alleviate their selective pressure and mitigate ARG proliferation in WWTPs. (Water Res, 2015)

      In our previous study, high levels of sulfonamide resistance genes were attributed to the selective pressure of the sulfonamide antibiotics. In addition to antibiotic selective pressure, in this study, the conjugative multi-resistant plasmids were characterized, and they were confirmed to contribute to the dissemination of antibiotic resistance genes in the Haihe River. Most of the isolated plasmids exhibited high transfer frequencies to the recipient strain Escherichia coli J53. Besides, a variety of the plasmid-borne ARGs were also the prevalent genes among of all the detected ARGs.This is the first study to investigate the overall distribution of conjugative plasmids which are attributable to proliferation of ARGs in a large river catchment scale. (Water Res, 2017)

   Ionic liquids (ILs), as “environmentally friendly” replacements for industrial volatile organic solvents, have been widely and recently applied in the chemical industry. However, few data have been collected regarding the toxicity and potential environmental effects of ILs, which are fairly important for preparing for their potential release into the environment.In this study, the IL 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]) was tested for its ability to promote the proliferation and dissemination of antibiotic resistance genes (ARGs) in environmental bacteria.In freshwater microcosms, [BMIm][PF6] significantly enhanced the abundance of the sulI gene. Meanwhile, [BMIm][PF6] significantly increased the abundance of class I integrons, which play a key role in ARG dissemination. Class I integron transfer experiments between different indigenous strains of Alcaligenes sp. (SMXR) and Acinetobacter sp. (StrR) were conducted to show that the horizontal transfer frequency of class I integrons was up to 88-fold higher in the presence of IL. IL increased cell membrane permeability as evidenced by flow cytometry (FCM), thereby assisting sulI gene transfer mediated by class I integrons. This is the first report that ILs facilitate the proliferation of ARGs in environmental bacteria and thus increase risks to public health.