Environmental obesogens contributed significantly to the obesity prevalence. Recently, antibiotics joined the list of environmental obesogens, while the underlying mechanisms remained to be explored. In the present study, effects of erythromycin (ERY), one widely used macrolide antibiotic, were measured on C. elegans to investigate the obesogenic mechanism. Results showed that ERY at 0.1 μg/L significantly increased the fat content by 17.4% more than the control and also stimulated triacylglycerol (TAG) levels by 25.7% more than the control. Regarding the obesogenic mechanisms, ERY provoked over-eating by stimulation on the pharyngeal pumping and reduction on the satiety quiescence percentage and duration. Such effects were resulted from stimulation on the neurotransmitters including serotonin (5-HT), dopamine (DA) and acetylcholine (ACh). The nervous responses involved the up-regulation of Gsα (e.g., ser-7, gsa-1, acy-1 and kin-2) signaling pathway and the down-regulation of TGFβ (daf-7) but not via cGMP-dependent regulations (e.g., egl-4). Moreover, ERY stimulated the activities of fatty acid synthase (FAS) and glycerol-3-phosphateacyl transferases (GPAT) that catalyze lipogenesis, while ERY inhibited those of acyl-CoA synthetase (ACS), carnitine palmitoyl transferase (CPT) and acyl-CoA oxidase (ACO) that catalyze lipolysis. The unbalance between lipogenesis and lipolysis resulted in the fat accumulation which was consistent with up-regulation on mgl-1 and mgl-3 which are the down-steam of TGFβ regulation. Such consistence supported the close connection between nervous regulation and lipid metabolism. In addition, ERY also disturbed insulin which connects lipid with glucose in metabolism.

The removal efficiency of antibiotic resistance genes (ARGs) is the biggest challenge for the treatment of erythromycin fermentation residue (EFR). In the current research, 0% (control), 10% (T1), and 30% (T2) spray-dried EFR were composted with bulking materials, consisting of cattle manure and maize straw, for 30 days. Environmental factors and bacterial community on the behaviors of ARGs were further investigated. Apart from the high levels of erythromycin, the electrical conductivities were also increased by 66.7% and 291.7% in the samples of T1 and T2, respectively. After 30 days of composting, total ARGs in the samples of control were decreased by 78.1%–91.2%, but those of T1 and T2 were increased 14.5–16.7- and 38.5–68.7-fold. ARGs related to ribosomal protection (erm) dominated the samples of T1 and T2 at D 13 and 30, especially that ermF accounted for more than 80% of the total ARGs. Furthermore, the results of bacterial community revealed that EFR promoted the growth of Proteobacteria and Bacteroidetes, but inhibited that of Actinobacteria, Verrucomicrobia and Chloroflexi. Network analysis revealed that the enriched ARGs had strong correlation with seven bacterial genera, including Halomonas, Oceanobacillus, and Alcaligenes, most of which are halotolerant. Above all, erythromycin combined with high salinity can have synergistic effect on the enrichment of ARGs and their hosts.

Heavy metal pollution and the potential for co-selection of resistance to antibiotics in the environment is growing concern. However, clear associations between heavy metals and antibiotic resistance in river systems have not been developed. Here we investigated relationships between total and bioavailable heavy metals concentrations; metal resistance gene (MRG) and antibiotic resistance gene (ARG) abundances; mobile genetic elements; and the composition of local bacterial communities in low and high metal polluted rivers in UK and India. The results indicated that MRGs conferring resistance to cobalt (Co) and nickel (Ni) (rcnA), and Co, zinc (Zn), and cadmium (Cd) (czcA), and ARGs conferring resistance to carbapenem and erythromycin were the dominating resistant genes across the samples. The relative MRGs, ARGs, and integrons abundances tended to increase at high metal polluted environments, suggesting high metals concentrations have a strong potential to promote metal and antibiotic resistance by horizontal gene transmission and affecting bacterial communities, leading to the development of multi-metal and multi-antibiotic resistance. Network analysis demonstrated the positive and significant relationships between MRGs and ARGs as well as the potential for integrons playing a role in the co-transmission of MRGs and ARGs (r > 0.80, p < 0.05). Additionally, the major host bacteria of various MRGs and ARGs that could be accountable for greater MRGs and ARGs levels at high metal polluted environments were also identified by network analysis. Spearman's rank-order correlations and RDA analysis further confirm relationships between total and bioavailable heavy metals concentrations and the relative MRG, ARG, and integron abundances, as well as the composition of related bacterial communities (r > 0.80 (or < −0.80), p < 0.05). These findings are critical for assessing the possible human health concerns associated with metal-driven antibiotic resistance and highlight the need of considering metal pollution for developing appropriate measures to control ARG transmission.

Bats are poorly understood as a reservoir of multidrug-resistant strains; therefore, the aim of this study was to determine molecular characterization of multidrug-resistant Enterococcus strains isolated from bat species from Poland. A multi-stage analysis based on targeted isolation of drug-resistant strains (selective media with tetracycline, chloramphenicol, gentamicin, streptomycin, and vancomycin), determination of the phenotypic profile of drug-susceptibility using the disc diffusion method, and amplification of DNA fragments surrounding rare restriction sites (ADSRRS-fingerprinting) was used for the isolation and differentiation of strains. The applied strategy finally allowed identification of E. faecalis resistant to at least one antimicrobial in 47.2% of the single-animal group and in 46.9% of the pooled samples of bat’s guano. Out of the 36 distinct isolates, 69% met the criteria of multi-drug resistance, with a dominant combination of resistance to tetracycline, erythromycin, and rifampicin. Simultaneously, 41.6% of the strains were high-level aminoglycoside resistant (HLAR). In most strains, phenotypic resistance was reflected in the presence of at least one gene encoding resistance to a given drug. Moreover, our research results show that some genes were detected simultaneously in the same strain statistically significantly more frequently. This may confirm that the spread of some genes (tetM and ermB or aph (3′)-IIIa as well as gelE and aac (6′)-Ie-aph (2″)-Ia or ant (6)-Ia) is associated with their common occurrence on the same mobile genetic element.To our knowledge, this is the first analysis of multidrug-resistance among E. faecalis isolated from bats. Our research demonstrates that the One Health concept is not associated exclusively with food-producing animals and humans, but other species of wildlife animals should be covered by monitoring programs as well.We confirmed for the first time that bats are an important reservoir of multi-resistant E. faecalis strains and could have a great impact on environmental resistance.

Pharmaceutically active compounds (PhACs) are widely found in the environment due to vast human consumption. Lots of work has been devoted to investigating the occurrence and seasonal variations globally. To fully understand characteristics and cross-year variation of PhACs in Beijing, 35 PhACs were analyzed in 46 sites across Beijing from both urban and suburban areas. Concentrations of target PhACs were ranged from levels of ng L⁻¹ to μg L⁻¹. Metoprolol (524 ng L⁻¹), caffeine (390 ng L⁻¹) and acetaminophen (156 ng L⁻¹) were the three most abundant non-antibiotics with the highest median concentration, and nalidixic acid (135 ng L⁻¹), erythromycin (64 ng L⁻¹) and sulfamethoxazole (77 ng L⁻¹) were the most abundant antibiotics. Urban and suburban areas are distinguished by PhAC composition in cluster analysis due to different wastewater collection rate. The ratio of easily removable compound group and hardly removable group was then proposed to reflect the wastewater collection rate. The compositional comparison of PhACs in WWTPs’ effluents and their receiving rivers further illustrates the impact of WWTPs in urban area. Higher proportion of antibiotics (>30%) in suburban area reflected the impact of presence of livestock farms, which should be concerned. Further statistical analyses show an improving trend of wastewater collection rate, and excluding metoprolol, an anti-hypertension medicine, the total concentration of 13 target PhACs was reduced by 72% during 2013–2017.

The occurrence of environmental antibiotic resistance genes (ARGs) are often attributed to selective pressure from antibiotics from point source pollution. However, the potential effects of natural production of antibiotics, environmental factors, and anthropogenic pressure on the development and spread of ARGs have not been fully investigated. This study evaluated the occurrence and distribution of erythromycin resistance methylase (erm) genes in urban soils. The ermA, ermB, ermC, ermD, ermF, ermG, ermT, and ermY genes were detected with detection frequencies ranging from 20% to 80% and abundances ranging between 5.95 × 101 and 6.94 × 106 copies g−1 dw soil. Both polyketide synthase (PKS) type I and type II biosynthesis genes—which are responsible for biosynthesis of polyketides, such as erythromycin—were detected in all soil samples with a range between 5.77 × 102 and 9.39 × 106 copies g−1 dw soil. The abundances of PKS genes were significantly correlated with 16S rRNA genes (r = 0.487 to 0.741, p < 0.001) and absolute abundances of ermB, ermC, ermD, ermG, and ermY (r = 0.302–0.490, p < 0.05), suggesting that the wide occurrence of ARGs in soils could be potentially driven by naturally produced antibiotics. Erythromycin was strongly correlated with ermB, ermC, ermF and ermY genes (r = 0.462 to 0.667, p < 0.05), but no significant correlation was observed between macrolides and PKS genes, suggesting other environmental factors may have contributed to detected macrolides. The fact that erm gene presented higher extent of variability than PKS genes in different land use types suggests that anthropogenic activity might also influence the occurrence of erm genes in urban soils.

In this study, antibiotic resistance to macrolide-lincosamide-streptogramin B (MLSB) antibiotics in total microbial community in surface water in a coastal urban city was measured using a modified fluorescence in situ hybridization (FISH) technique. This FISH technique quantified the rate of antibiotic resistance to MLSB antibiotics through targeting methylation site of A2058 of 23S rRNAs resulting from expressed erythromycin ribosome methylation (erm) genes. Correlations between the rates of MLSB resistance measured by FISH and macrolide concentrations was stronger than that between the relative abundance of erm genes and macrolide concentrations, especially in residential areas where the main detected antibiotics were macrolides. These results suggest that trace levels of antibiotics in environmental waters, which was as low as 40 ng L−1, may still play important roles in the development and spread of antibiotic resistance. Additionally, methylation as a result of erm gene expression, instead of erm gene abundance, was a better indicator of selective pressure of trace level macrolides. The rates of MLSB resistance varied significantly among land use types, suggesting that anthropogenic activities are important factors to select for erm gene expression in the environment. Microbial community analysis of representative surface water samples showed that relatively high rates of MLSB resistance were observed in Alphaproteobacteria (42%), Acidobacteria (36%), Bacteroidaceae (32%), Chloroflexi (27%), and Betaproteobacteria (20.2%).

A mesocosm case study was conducted to gain understanding and practical knowledge on biofilm emerging contaminants biodegradation capacity under stressor and multiple stressor conditions. Two real life scenarios: I) biodegradation in a pristine intermittent stream experiencing acute pollution and II) biodegradation in a chronically polluted intermittent stream, were examined via a multifactorial experiment using an artificial stream facility. Stream biofilms were exposed to different water flow conditions i.e. permanent and intermittent water flow. Venlafaxine, a readily biodegradable pharmaceutical was used as a measure of biodegradation capacity while pollution was simulated by a mixture of four emerging contaminants (erythromycin, sulfisoxazole, diclofenac and imidacloprid in addition to venlafaxine) in environmentally relevant concentrations. Biodegradation kinetics monitored via LC-MS/MS was established, statistically evaluated, and used to link biodegradation with stress events. The results suggest that the effects of intermittent flow do not hinder and may even stimulate pristine biofilm biodegradation capacity. Chronic pollution completely reduced biodegradation in permanent water flow experimental treatments while no change in intermittent streams was observed. A combined effect of water flow conditions and emerging contaminants exposure on biodegradation was found. The decrease in biodegradation due to exposure to emerging contaminants is significantly greater in streams with permanent water flow suggesting that the short and medium term biodegradation capacity in intermittent systems may be preserved or even greater than in perennial streams.

Erythromycin is an antibiotic employed in the treatment of infections caused by Gram positive microorganisms and the increasing use has made it a contaminant of emerging concern in aqueous ecosystems. Cerium oxide nanoparticles (CeO₂ NPs), which are known to have catalytic and antioxidant properties, have also become contaminants of emerging concern. Due to the high reactivity of CeO₂ NPs, they can interact with erythromycin magnifying their effects or on the other hand, considering the redox potential of CeO₂ NPs, it can alleviate the toxicity of erythromycin. The present study was carried out to assess the toxicity of both single compounds as well as mixed on Chlamydomonas reinhardtii and Phaeodactylum tricornutum (freshwater and marine microalgae respectively) employed as target species in ecotoxicological tests. Mechanisms of oxidative damage and those harmful to the photosynthetic apparatus were studied in order to know the toxic mechanisms of erythromycin and the joint effects with CeO₂ NPs. Results showed that erythromycin inhibited the microalgae population growth and effective quantum yield of PSII (E.Q.Y.) in both microalgae. However, the freshwater microalgae Chlamydomonas reinhardtii was more sensitive than the marine diatom Phaeodactylum tricornutum. Responses related to the photosynthetic apparatus such as E.Q.Y. was affected by the exposure to erythromycin of both microalgae, as chloroplasts are target organelle for this antibiotic.Mixed experiments (CeO₂ NPs + erythromycin) showed the protective role of CeO₂ NPs in both microalgae preventing erythromycin toxicity in toxicological responses such as the growth of the microalgae population and E.Q.Y.

Antibiotics are added to agricultural fields worldwide through wastewater irrigation or manure application, resulting in antibiotic contamination and elevated environmental risks to terrestrial environments and humans. Most studies focused on antibiotic detection in different matrices or were conducted in a hydroponic environment. Little is known about the transfer of antibiotics from antibiotic-contaminated irrigation wastewater and animal manure to agricultural soil and edible crops. In this study, we evaluated the transfer of five different antibiotics (tetracycline, sulfamethazine, norfloxacin, erythromycin, and chloramphenicol) to different crops under two levels of antibiotic-contaminated wastewater irrigation and animal manure fertilization. The final distribution of tetracycline (TC), norfloxacin (NOR) and chloramphenicol (CAP) in the crop tissues under these four treatments were as follows: fruit > leaf/shoot > root, while an opposite order was found for sulfamethazine (SMZ) and erythromycin (ERY): root > leaf/shoot > fruit. The growth of crops could accelerate the dissipation of antibiotics by absorption from contaminated soil. A higher accumulation of antibiotics was observed in crop tissues under the wastewater treatment than under manure treatment, which was due to the continual irrigation that increased adsorption in soil and uptake by crops. The translocation of antibiotics in crops mainly depended on their physicochemical properties (e.g. log Kow), crop species, and the concentrations of antibiotics applied to the soil. The levels of antibiotics ingested through the consumption of edible crops under the different treatments were much lower than the acceptable daily intake (ADI) levels.