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Chlorine disinfection to drinking water plays an important role in preventing and controlling waterborne disease outbreaks globally. Nevertheless, little is known about why it enriches the antibiotic resistance genes (ARGs) in bacteria after chlorination. Here, ARGs released from killed antibiotic-resistant bacteria (ARB), and culturable chlorine-injured bacteria produced in the chlorination process as the recipient, were investigated to determine their contribution to the horizontal transfer of ARGs during disinfection treatment. We discovered Escherichia coli, Salmonella aberdeen, Pseudomonas aeruginosa and Enterococcus faecalis showed diverse resistance to sodium hypochlorite, and transferable RP4 could be released from killed sensitive donor consistently. Meanwhile, the survival of chlorine-tolerant injured bacteria with enhanced cell membrane permeabilisation and a strong oxidative stress-response demonstrated that a physiologically competent cell could be transferred by RP4 with an improved transformation frequency of up to 550 times compared with the corresponding untreated bacteria. Furthermore, the water quality factors involving chemical oxygen demand (CODMn), ammonium nitrogen and metal ions (Ca2+ and K+) could significantly promote above transformation frequency of released RP4 into injured E. faecalis. Our findings demonstrated that the chlorination process promoted the horizontal transfer of plasmids by natural transformation, which resulted in the exchange of ARGs across bacterial genera and the emergence of new ARB, as well as the transfer of chlorine-injured opportunistic pathogen from non-ARB to ARB. Considering that the transfer elements were quite resistant to degradation through disinfection, this situation poses a potential risk to public health.

Additional file 1: Table S1. Primers of ARGs for conventional PCR. Table S2. Primers of ARGs and 16S rRNA for quantitative PCR. Table S3. Standard curves of ARGs and 16S rRNA for quantitative PCR. Table S4. Concentration and purity of standard plasmid of ARGs. Table S5. Primers of housekeeping genes of s. epidermidis [13]. Table S6. Effect of gender on thefrequencies of fecal resistance genes in newborns. Table S7. Difference and association of the frequencies of blaTEM in colostrums and the feces on the third day of newborns. Table S8. Difference and association of the frequencies of ampC in colostrums and the feces on the third day of newborns. Table S9. Difference and association of the frequencies of tetM in colostrums and the feces on the third day of newborns. Table S10. Difference and association of the frequencies of aac(6���)-Ib in colostrums and the feces on the third day of newborns. Table S11. Difference and association of the frequencies of ermB in colostrums and the feces on the third day of newborns. Table S12. Difference and association of the frequencies of sul2 in colostrums and the feces on the third day of newborns. Table S13. Difference and association of the frequencies of mecA in colostrums and the feces on the third day of newborns. Figure S1. The median of ARGs amount in the feces of six newborns on 3th day, 7th day and 30th day, respectively. Table S14. ST number of Staphylococcus epidermidis isolated from colostrum. Table S15. ST number of Staphylococcus epidermidis isolated from faeces on the third day. Table S16. ST number of Staphylococcus epidermidis isolated from ward air. Table S17. Resistance phenotypes and ARGs of Staphylococcus epidermidis isolated from colostrum. Table S18. Resistance phenotypes and ARGs of Staphylococcus epidermidis isolated from faeces on third day. Table S19. Resistance phenotypes and ARGs of Staphylococcus epidermidis isolated from ward air.

The latent dangers of waterborne viral transmission have become a major public health concern. In this study, reduced graphene oxide (rGO)-Fe3O4 nanoparticles were decorated with cetyltrimethylammonium bromide (CTAB) to adsorb severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike pseudovirus and three human enteric viruses (HuNoV, HRV, and HAdV). The successful combination of CTAB with rGO-Fe3O4 was confirmed by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, zeta potential, Brunner-Emmet-Teller, and vibrating sample magnetometer measurements. The adsorption of HuNoV and HAdV followed pseudo-first-order kinetics, while that of HRV conformed to the pseudo-second-order model. CTAB-functionalized rGO-Fe3O4 exhibited exceptionally high adsorption of HuNoV, HRV, HAdV and SARS-CoV-2 spike pseudovirus, with maximum adsorption capacities of 3.55 × 107, 7.01 × 107, 2.21 × 107 and 6.92 × 106 genome copies mg−1, respectively. Moreover, the composite could effectively adsorb the four types of virus particles from coastal, tap, and river water. In addition, concentrating the virions using CTAB functionalized rGO-Fe3O4 composites before qPCR analysis significantly improved the detection limit. The results indicate that viruses are captured on the surface of CTAB functionalized rGO-Fe3O4 composites through electrostatic interactions and the intrinsic adsorption ability of rGO. Overall, CTAB-functionalized rGO-Fe3O4 composites are promising materials for the adsorption and detection of human enteric viruses as well as SARS-CoV-2 from complex aqueous environments., Graphical abstract Image 1

Given its excellent performance against the pathogens, UV disinfection has been applied broadly in different fields. However, only limited studies have comprehensively investigated the response of bacteria surviving UV irradiation to the environmental antibiotic stress. Here, we investigated the antibiotic susceptibility of Pseudomonas aeruginosa suffering from the UV irradiation. Our results revealed that UV exposure may decrease the susceptibility to tetracycline, ciprofloxacin, and polymyxin B in the survival P. aeruginosa. Mechanistically, UV exposure causes oxidative stress in P. aeruginosa and consequently induces dysregulation of genes contributed to the related antibiotic resistance genes. These results revealed that the insufficient ultraviolet radiation dose may result in the decreased antibiotic susceptibility in the pathogens, thus posing potential threats to the environment and human health.

An unhealthy diet has been linked to increased incidence of chronic diseases. To investigate the relationship between diet and intestinal inflammation, mice in two experimental groups were fed on a high-fat diet or high-fructose diet, respectively. The result showed that the defecation volume of the experimental groups was significantly reduced compared with that of the control group, and the levels of pro-inflammatory cytokines (interleukin (IL)-1β and IL-6) and IgG in serum were increased significantly. In addition, inflammatory cell infiltration was observed in intestinal tissue, indicating that a high-fructose or high-fat diet can lead to constipation and inflammation. Further analysis showed that the microbial composition of the experimental groups changed significantly, including a decrease of the Bacteroidetes/Firmicutes ratio and increased levels of Bacteroides, Akkermansia, Lactobacillus, and Ruminococcus, which might be associated with inflammation. The results of pro-inflammatory metabolites analysis showed that the levels of arachidonic acid, stearic acid, and indoxylsulfuric acid were significantly increased in the experimental groups, which were related significantly to Bacteroides, Enterococcus, and Akkermansia. Meanwhile, the content of 5-hydroxytryptamine (5-HT) was significantly decreased, which might cause constipation by reducing intestinal peristalsis. Moreover, transplantation of fecal bacteria from inflammatory mice caused constipation and inflammation in normal mice, which could be relieved by feeding a normal diet. The results of the present study indicated that changes in intestinal microbiota and microbial metabolites may underlie chronic intestinal inflammation and constipation caused by high-fructose and high-fat diets.

Enteric viruses exposed to water pose a huge threat to global public health and can lead to waterborne disease outbreaks. A sudden increase in enteric viruses in some water matrices also underpins the prevalence of corresponding waterborne diseases in communities over the same time period. However, few efforts have been focused on water matrices whose viral pollution may best reflect the clinical prevalence in communities. Here, a one-year surveillance of human enteric viruses including Enteroviruses (EnVs), Rotaviruses (HRVs), Astroviruses (AstVs), Noroviruses GII (HuNoVsGII) and Mastadenoviruses (HAdVs) in four representative water matrices: an urban river (UR) running through city, effluent from Wastewater Treatment Plant (EW), raw water for Urban Water Treatment Plant (RW), and tap water (TW) were performed by qPCR. The relationship between the virus detection frequency at each site and their prevalence in clinical PCR assay was further analyzed. We found that the detection frequencies of HRVs, HuNoVsGII, and AstVs in stools peaked in winter, while EnVs peaked in autumn. No EnVs occurred in EW, RW, or TW, but HuNoVsGII and AstVs occurred intensively in winter. For UR, all types of enteric viruses could be detected and the levels of acute gastroenteritis viruses (HRVs, HuNoVsGII, AstVs, and HAdVs) were highest in autumn or winter, whereas EnVs peaked in summer. In terms of correlation analyses, only HRVs and HuNoVsGII levels in UR showed a strong positive correlation with their prevalence in clinical stool samples. This study indicated that HRVs and HuNoVsGII levels in URs may mirror the local virus prevalence, thereby implying the possibility of revealing their local epidemiology by monitoring them in the URs., Graphical abstract Unlabelled Image, Highlights • Correlation of enteric virus in water matrices and clinical prevalence were analyzed. • The virus abundance in wastewater effluents has no correlation with local prevalence. • HRVs and HuNoVsGII in urban rivers positively correlated with clinical prevalence.

Antibiotic residues in the environment pose a great risk to global public health. They increase antibiotic resistance by enhancing plasmid conjugation among bacteria or mutations within bacterial genomes. However, little is known about whether the putative environmental levels of antibiotics are sufficient to influence plasmid-mediated transformability. In this study, we explored the effect of eight kinds of representative antibiotics and several other compounds on the plasmid transformability of competent Escherichia coli. Only levofloxacin (LEV) at the putative environmental levels was found to facilitate the frequency of PBR322-or RP4-plasmid-mediated transformation by up to 5.3-fold. Additionally, PBR322 transformation frequency could be further enhanced by copper ion or ammonia nitrogen but inhibited by humic acid. However, when competent E. coli was exposed to the minimal inhibitory concentrations (MIC) of the antibiotics, an enhanced plasmid-assimilation ability was observed and plasmid transformation frequency was increased by up to 98.6-fold for all the tested antibiotics. Furthermore, E. coli exhibited a preference for the uptake of plasmids harbouring the resistance genes to the antibiotics it had been exposed to. Among these antibiotics, cephalexin, tetracycline, and kanamycin induced the highest uptake of RP4. The putative environmental levels of LEV enhanced plasmid transformability regardless of the presence of corresponding antibiotic resistance gene (ARG) on the genetic elements, suggesting environmental LEV residues may facilitate dissemination of antibiotic resistance by any plasmid-mediated transformability, thereby posing a great risk to health.

The rapid spread of antibiotic resistance genes (ARGs) is a great challenge to the ecological safety and human health. The intestine of humans and animals is an important site for the increase and spread of ARGs due to the great diversity and abundance of microorganisms in the intestinal microecology. ARGs, including the intracellular (iARGs) and the extracellular (eARGs) ARGs, are usually introduced into the intestinal tract through the diet, and the iARGs are colonized and spread in the intestinal microbiota with the help of the host bacteria. However, whether the eARGs can enter the intestinal microorganisms in the absence of host bacteria is not known. Here, we show the transformation and the diffusion of the ampramycin resistance gene (Ap) carried by the free plasmid RK2 in the intestinal microbiota of mice. After two days of consecutive gavage with free RK2, the intracellular Ap gene increases from days 0-8 in the feces of mice, and has remained constant. Bacterial transformation happens in the small intestine, including proximal and distal jejuna and proximal and distal ilea, at the early stage (first two days), and the intracellular RK2 is diffused into the intestinal microbiota of mice by conjugation on days 2-8 day, which is based on the distribution of eARG and iARG and the mRNA expression levels of trbBp, trfAp, korA, korB, and trbA. The characteristics of ARGs susceptible microbiota for transformation are analyzed using 16s rRNA gene sequencing, transmission electron microscopy, and flow cytometric. The ingestion of RK2 affects the composition of intestinal microbiota especially for Proteobacteria, and the antibiotic residue promotes the increase in Escherichia coli. These findings are important to assess the risk of ARGs, especially the eARGs in the intestinal microecology.