Characterization and source identification of tetracycline antibiotics in the drinking water sources of the lower Yangtze River

Enrichment of antibiotics in an inland lake water

Inland water is very susceptible to the input of pollutants. However, little is known about the occurrence of antibiotics in inland lakes. In this study, a total of 83 target antibiotics were quantified in water and sediment samples collected from the Qinghai Lake, the largest inland lake of China located on the northeast of Qinghai-Tibet plateau, and its inflowing rivers. The results showed that 27 and 25 antibiotics were detected in water and sediments, respectively, with the summed concentrations (SUM) of 1.14-17.3 ng/L and 0.72-8.31 ng/g. Compared with the input rivers, significantly higher levels of sulfonamides (SAs), quinolones (QNs), polyethers (PEs), and SUM in water samples were observed in Qinghai Lake water. The average proportions of SAs (50.9-52.7%) and QNs (22.0-28.3%) in Qinghai Lake water nearly doubled compared to those in input rivers. An enrichment factor (EF) was proposed to reveal the enrichment degree of antibiotics in Qinghai Lake compared to its input river water. Sulfaguanidine (SGD), flumequine (FLU), and nalidixic acid (NDA) were enriched in Qinghai Lake up to several ten times based on the calculated EF values, due to their persistence in such a cold saline lake. Risk assessment showed that most antibiotics except anhydrochlortetracycline (ACTC) had insignificant risks to aquatic organisms and antibiotic resistance selection in Qinghai Lake water. This study was the first to reveal the enrichment of antibiotics in Qinghai Lake water, and suggests the urgent need to investigate the possible long-term enrichment and environmental risks of antibiotics in inland lakes.

Microbial degradation of tetracycline in the aquatic environment: a review

Tetracycline residues have frequently been detected in multi-environmental media, and it could induce antibiotic resistance genes (ARGs) in microorganisms, which has attracted great attention. Where biodegradation processes may be a promising strategy to remove tetracycline. Thus, this study mainly considers: (i) the degradation of tetracycline by microorganisms including single microorganisms and microbial flora; (ii) the elimination of tetracycline during biochemical treatment processes and advanced treatment systems in wastewater treatment plants (WWTPs) and constructed wetlands (CWs); (iii) the degradation of tetracycline by biological coupling processes; (iv) the confusion and problem of tetracycline biodegradation. Furthermore, the characteristics and comparison of tetracycline biodegradation have been discussed in detail. Additionally, future research directions are suggested to reduce tetracycline in the aquatic environment, especially tetracycline biodegradation and the nitrogen conversion process. Highlights Degradation of tetracycline by pure culture strains and microflora was significant. Degradation of tetracycline by biochemical treatment process was summarized. Advanced treatment process in CWs could eliminate tetracycline. Future research directions on biodegradation of tetracycline are proposed.

Cleaning up China's Medical Cabinet-An Antibiotic Take-Back Programme to Reduce Household Antibiotic Storage for Unsupervised Use in Rural China: A Mixed-Methods Feasibility Study

: Background: Antibiotic misuse and unsafe disposal harm the environment and human health and contribute to the global threat of antimicrobial resistance. Household storage of antibiotics for unsupervised use and careless disposal of medications is a common practice in China and most low- and middle-income countries. Currently, few interventions are available to address this challenge.

OBJECTIVE

This study assesses the feasibility and acceptability of an evidence-based, theory-informed, community-based take-back programme for disposing household's expired, unwanted, or unused antibiotics in rural China.

METHODS

We adopted the RE-AIM framework and the community-based participatory research principles in the development, implementation, and evaluation of the intervention. The RE-AIM (reach, effectiveness, adoption, implementation, and maintenance) and Medical Research Council's frameworks were employed in analysing and reporting evaluation results. A mixed-methods, controlled pre-and post-test design was used for 1) quantitative surveying of a representative community panel of 50 households, and 2) qualitative semi-structured stakeholders' interviews to explore intervention and study design feasibility and acceptability at three phases: pre-intervention, intervention, and post-intervention. Quantitative and qualitative data from a similar village-serving as a control-were also collected.

RESULTS

All a priori feasibility objectives were met: Conversion to consent was 100.0% (100 screened, approached, recruited, and consented). All participants completed the pre-intervention assessment, and 44/50 households in the intervention village completed the post-intervention assessment. The programme, embedded in existing social and physical infrastructure for dissemination, directly reached over 68.2% (30/44) of its target audience. Stakeholders reported the intervention and study design as feasible and acceptable.

CONCLUSIONS

This study illustrates the feasibility, acceptability, and potential efficacy of community-based antibiotic take-back programmes in China to encourage safe disposal and decrease the availability of expired, unwanted, or unused antibiotics in the household for unsupervised use.

Decision-Making Tools to Manage the Microbiology of Drinking Water Distribution Systems

This paper uses a two-fold multi-criteria decision-making (MCDM) approach applied for the first time to the field of microbial management of drinking water distribution systems (DWDS). Specifically, the decision-making trial and evaluation laboratory (DEMATEL) was applied removing the need for reliance on expert judgement, and analysed interdependencies among water quality parameters and microbiological characteristics of DWDS composed of different pipe materials. In addition, the fuzzy technique for order preference by similarity to ideal solution (FTOPSIS) ranked the most common bacteria identified during trials in a DWDS according to their relative abundance while managing vagueness affecting the measurements. The novel integrated approach presented and proven here for an initial real world data set provides new insights in the interdependence of environmental conditions and microbial populations. Specifically, the application shows as the bacteria having associated the most significant microbial impact may not be the most abundant. This offers the potential for integrated management strategies to promote favourable microbial conditions to help safeguard drinking water quality.

The removal of tetracycline, oxytetracycline, and chlortetracycline by manganese oxide-doped copper oxide: the behaviors and insights of Cu-Mn combination for enhancing antibiotics removal

Adsorption process is suitable to the advanced treatment of tetracycline antibiotics (TCs; including tetracycline (TTC), oxytetracycline (OTC), and chlortetracycline (CTC)) in poultry wastewater. In this research, Mn oxide-doped Cu oxide (MODCO) was synthesized and used for the removal of TTC, OTC, and CTC. According to the XRD and SEM analysis results, MODCO has an amorphous crystal structure and is formed by the aggregation of nano-sized particles with a uniform distribution of Cu and Mn elements. In addition, MODCO has a BET surface area of 67.7 m²/g and a pH_IEP value of 7.8. The results of batch experiments illustrated that the reaction rates for the removal of three TCs were in the order of OTC > CTC > TTC. In addition, the theoretical maximum amounts of TTC, OTC, and CTC adsorbed on MODCO were determined to be 2.90 mmol/g, 4.15 mmol/g, and 2.20 mmol/g via the Langmuir model, respectively. The optimal removal performances of TCs were achieved in the pH range of 6~9, and the coexistence of anions posed an unnoticeable effect on the removal efficiencies. The spectroscopic analysis results demonstrated that the removal mechanism of TCs was mainly attributed to surface complexation. Furthermore, a part of TCs may be decomposed by Mn oxides during the removal process according to the UV spectrogram results. Overall, MODCO has exhibited a great potential for the removal of TCs from aqueous solution.

Dry and wet seasonal variation of total mercury, inorganic mercury, and methylmercury formation in estuary and harbor sediments

This study analyzed the seasonal variations and the spatial distributions of total mercury (THg), inorganic divalent mercury (IHg), and methylmercury (MeHg) in sediments of river mouth (RM), main channel (MC), and entrance (E) of the Port of Kaohsiung, Taiwan. The THg, IHg, and MeHg concentrations were, respectively, 198-9130, 2.6-3164, and <0.3-42.6 μg/kg in the wet season and 362-2264, 11.0-790, and 3.3-65.6 μg/kg in the dry season. As for seasonal variations, the concentrations of THg and IHg for RM sediment were higher in the wet season than in the dry season, whereas for MC and E was converse. Generally, MeHg in sediment was higher in the dry season than in the wet season. THg and IHg were mainly transported from the river, whereas MeHg was generated by onsite microbes transforming the local available IHg. Results indicated that the formation of MeHg in sediment may be mainly influenced by the concentration of IHg and seasonal variations.

Effects of rainfall events on behavior of tetracycline antibiotics in a receiving river: Seasonal differences in dominant processes and mechanisms

Tetracycline (TC) antibiotics are widely used in livestock and poultry breeding. However, limited work has been done on the partition of TCs between suspended sediment (SPS) and overlying water or on the seasonal effects of rainfall events on the behavior of TCs in receiving rivers. Here, we assessed the impacts of rainfall events in different seasons on the concentrations and fate of TCs in a typical watershed. Concentrations of TCs in river water, SPS, and surface sediment were determined before, during, and after rainfall events. Results indicated that the sequence of TC concentration levels in river water was wet season > normal season > dry season. Rainfall events in all seasons increased the concentrations of TCs in river water. The concentration of TCs in SPS reached 104 ng/g. The SPS concentrations were only 22-78 mg/L, while the daily fluxes of TCs in particulate form contributed 39%-62% of the total (dissolved and particulate) daily fluxes in river water. The increases in TCs in river water were mainly attributed to internal release from sediment during rainfall events in the dry season but to external input during rainfall events in the wet season. The degradation products of TCs with higher concentrations and greater toxicity than their parent compounds should be considered in the ecological risk assessment of TCs. This research demonstrated that manure application should not be conducted in the normal season or before rainfall events, especially heavy rainfall.