Prevalence and pollution characteristics of antibiotic resistant genes in one high anthropogenically-impacted river

Seasonal hydrological dynamics affected the diversity and assembly process of the antibiotic resistome in a canal network

The significant threat of antibiotic resistance genes (ARGs) to aquatic environments health has been widely acknowledged. To date, several studies have focused on the distribution and diversity of ARGs in a single river while their profiles in complex river networks are largely known. Here, the spatiotemporal dynamics of ARG profiles in a canal network were examined using high-throughput quantitative PCR, and the underlying assembly processes and its main environmental influencing factors were elucidated using multiple statistical analyses. The results demonstrated significant seasonal dynamics with greater richness and relative abundance of ARGs observed during the dry season compared to the wet season. ARG profiles exhibited a pronounced distance-decay pattern in the dry season, whereas no such pattern was evident in the wet season. Null model analysis indicated that deterministic processes, in contrast to stochastic processes, had a significant impact on shaping the ARG profiles. Furthermore, it was found that Firmicutes and pH emerged as the foremost factors influencing these profiles. This study enhanced our comprehension of the variations in ARG profiles within canal networks, which may contribute to the design of efficient management approaches aimed at restraining the propagation of ARGs.

Micro-algae assisted green bioremediation of water pollutants rich leachate and source products recovery

Water management and treatment are high concern fields with several challenges due to increasing pollutants produced by human activity. It is imperative to find integral solutions and strategic measures with robust remediation. Landfill leachate production is a high concern emerging problem. Especially in low middle-income countries due to no proper local waste disposition regulation and non-engineered implemented methods to dispose of urban waste. These landfills can accumulate electronic waste and release heavy metals during the degradation process. Similar phenomena include expired pharmaceuticals like antibiotics. All these pollutants accumulated in leachate made it hard to dispose of or treat. Leachate produced in non-engineered landfills can permeate soils and reach groundwater, dragging different contaminants, including antibiotics and heavy metals, which eventually can affect the environment, changing soil properties and affecting wildlife. The presence of antibiotics in the environment is a problem with particular interest to solve, mainly to avoid the development of antibiotic-resistant microorganisms, which represent a future risk for human health with possible epidemic implications. It has been reported that the use of contaminated water with heavy metals to produce and grow vegetables is a risk for consumers, heavy metals effects in humans can include carcinogenic induction. This work explores the opportunities to use leachate as a source of nutrients to grow microalgae. Microalgae stand out as an alternative to bioremediate leachate, at the same time, microalgae produce high-value compounds that can be used in bioplastic, biofuels, and other industrial applications.

River Biofilms Microbiome and Resistome Responses to Wastewater Treatment Plant Effluents Containing Antibiotics

Continuous exposure to low concentrations of antibiotics (sub-minimal inhibitory concentration: sub-MIC) is thought to lead to the development of antimicrobial resistance (AMR) in the environmental microbiota. However, the relationship between antibiotic exposure and resistance selection in environmental bacterial communities is still poorly understood and unproven. Therefore, we measured the concentration of twenty antibiotics, resistome quality, and analyzed the taxonomic composition of microorganisms in river biofilms collected upstream (UPS) and downstream (DWS) (at the point of discharge) from the wastewater treatment plant (WWTP) of Poitiers (France). The results of statistical analysis showed that the antibiotic content, resistome, and microbiome composition in biofilms collected UPS were statistically different from that collected DWS. According to Procrustes analysis, microbial community composition and antibiotics content may be determinants of antibiotic resistance genes (ARGs) composition in samples collected DWS. However, network analysis showed that the occurrence and concentration of antibiotics measured in biofilms did not correlate with the occurrence and abundance of antibiotic resistance genes and mobile genetic elements. In addition, network analysis suggested patterns of co-occurrence between several ARGs and three classes of bacteria/algae: Bacteroidetes incertae sedis, Cyanobacteria/Chloroplast, and Nitrospira, in biofilm collected UPS. The absence of a direct effect of antibiotics on the selection of resistance genes in the collected samples suggests that the emergence of antibiotic resistance is probably not only due to the presence of antibiotics but is a more complex process involving the cumulative effect of the interaction between the bacterial communities (biotic) and the abiotic matrix. Nevertheless, this study confirms that WWTP is an important reservoir of various ARGs, and additional efforts and legislation with clearly defined concentration limits for antibiotics and resistance determinants in WWTP effluents are needed to prevent their spread and persistence in the environment.

Sunlight Photolysis of Extracellular and Intracellular Antibiotic Resistance Genes tetA and sul2 in Photosensitizer-Free Water

Antibiotic resistance genes (ARGs; the genetic material in bacteria that encode for resistance to antibiotics) have been found in the aquatic environment, raising concerns of an environmental transmission route. In an effort to contribute to models predicting the fate of ARGs in the environment-to design control measures, predict health risks, inform ARG surveillance activities, and prioritize policy interventions-and given the importance of sunlight in damaging DNA, we evaluated the sunlight photolysis kinetics of antibiotic-resistant bacteria (ARB) and ARGs under laboratory conditions, focusing on Escherichia coli SMS-3-5 and its ARGs tetA and sul2. Experiments were conducted in the absence of photosensitizers, and ARG decay rates were quantified by quantitative polymerase chain reaction (qPCR) with short and long amplicon targets. Long amplicon qPCR targets quantified greater photolysis rate constants, due to greater ARG coverage. After a lag phase, intracellular ARG had faster decay rates than extracellular ARG, likely due to the contribution of intracellular indirect photolysis processes. Furthermore, all ARG decay rates were significantly slower than those of E. coli. Decay rate constants and quantum yields are presented as foundational work in the development of models to describe the persistence of ARGs in sunlit, environmental waters.

Enrichment of antibiotic resistance genes (ARGs) in polyaromatic hydrocarbon-contaminated soils: a major challenge for environmental health

Polyaromatic hydrocarbons (PAHs) are widely spread ecological contaminants. Antibiotic resistance genes (ARGs) are present with mobile genetic elements (MGE) in the bacteria. There are molecular evidences that PAHs may induce the development of ARGs in contaminated soils. Also, the abundance of ARGs related to tetracycline, sulfonamides, aminoglycosides, ampicillin, and fluoroquinolones is high in PAH-contaminated environments. Genes encoding the efflux pump are located in the MGE and, along with class 1 integrons, have a significant role as a connecting link between PAH contamination and enrichment of ARGs. The horizontal gene transfer mechanisms further make this interaction more dynamic. Therefore, necessary steps to control ARGs into the environment and risk management plan of PAHs should be enforced. In this review, influence of PAH on evolution of ARGs in the contaminated soil, and its spread in the environment, has been described. The co-occurrence of antibiotic resistance and PAH degradation abilities in bacterial isolates has raised the concerns. Also, presence of ARGs in the microbiome of PAH-contaminated soil has been discussed as environmental hotspots for ARG spread. In addition to this, the possible links of molecular interactions between ARGs and PAHs, and their effect on environmental health has been explored.