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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

Adaption to adverse environments plays an important role in bacterial survival and is receiving increasing globe attention now. Here, cultivable chlorine-injured Pseudomonas aeruginosa, produced on the chlorination process, was investigated about their resistance to antibiotics. Then, global transcriptional analyses, quantitative PCR (qPCR) validation and antioxidant enzymes measurement were performed to explore the underlying mechanisms. The results showed that chlorine injury enhanced antibiotic resistance in P. aeruginosa and cultivable chlorine-injured P. aeruginosa exposed to 4 mg/L sodium hypochlorite (half of the lethal dose) improved antibiotic resistance against ceftazidime, chloramphenicol and ampicillin by 1.4–5.6 fold. This increase in antibiotic resistance was not hereditable and over expression of the MexEF-OprN efflux pump resulting from oxidative stress contributed to it. These results demonstrate temporal physiological persistence to antibiotics in cultivable chlorine-injured pathogens, suggesting their survival from adverse environments with antibiotic exposure and thereby posing lasting hazards to human health.

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.

Occurrence of human enteric viruses in coastal water poses a high public health risk upon exposure for swimmers. However, it is difficult to detect viruses directly due to their low concentrations in the coastal water; this demands concentration of adequate amounts of viruses from large volumes of coastal water before viral detection. Here, we explored a filter cartridge system with electropositive granule media (EGM) for recovery of viruses from coastal water for the first time. The viruses were assayed by TaqMan-based quantitative PCR (qPCR). To optimize the tool, operational parameters of the EGM filter and the effect of coastal water quality on virus recovery were investigated. Furthermore, the filter's effectiveness was validated by analyzing the recovery of various enteric viruses and comparing the recovery rates with those of tangential flow filtration (TFF). The EGM filter could recover more than 88% of the enteric viruses including astroviruses (AstVs), noroviruses (HuNoVs GII) and adenoviruses (HAdVs) from coastal water with the established optimal protocol in comparison with TFF (52.5%). Recovery rates remained high under varied coastal water quality conditions including pH (5 to 9), temperature (4 to 32 °C), chemical oxygen demand level (CODMn) below 4 mg L−1, ammonium concentration (NH3–N) below 2 mg L−1, and viral loads below 1012 GCs. The findings suggest that the EGM filter provides an efficient approach for concentrating viruses from large volumes of coastal water (ranging from 10 L to 100 L), which can be a useful tool in monitoring sparsely existing viruses in coastal water.

Background: The human gut harbors trillions of microbes, strongly bearing great importance for the health of the host. However, the effect of drinking water on gut microbiota has been poorly understood. Results: In this study, we explored the response of BALB/c mice gut bacterial community (feces) to the different types of drinking water, including commercial bottled mineral water(MW), natural water(NW), purified water(PW) and tap water(TW). Feces were cultured with Brain Heart Infusion Broth dissolved in 4 types of drinking water. 16S rRNA sequencing analysis was performed. Our results reveal that the gut microbiota composition is different among culturing with 4 types of drinking water. As the culture time increases, the number of OTUs significantly decreased except under the aerobic condition of MW. Under the aerobic condition in the 5th day, the considerable differences of alpha diversity index are found between MW and 3 others, consistent to that there are the most unique taxa in MW group. Importantly, the LEfSe analysis discovers that the Bacteroidetes taxa dominate the differences between MW and the other water types. Conclusion: our findings demonstrate that the mineral water can lead to a progressive increase of the microbiota diversity by providing the growth convenience to Bacteroidetes.

Human enteric virus occurrence in bathing beaches poses a potential health risk to swimmers. They may come from several sources, but the understanding of the seasonal contribution of contamination sources to virus occurrence is still lacking. Here, the surveillance of human enteric viruses at the First Bathing Beach in Qingdao was performed January-December 2018. The occurrence of Enteric viruses, assayed with quantitative polymerase chain reaction (qPCR), was analyzed at temporal and spatial levels to determine the viral contamination sources. The results showed that only Astroviruses (AstVs) and Adenoviruses (HAdVs) were found in the swimming area. Their occurrence correlated significantly with the sewage-polluted area, but HAdVs were only found in autumn and AstVs in spring. Meanwhile, enteric viruses in the swimming area showed significantly higher levels than the surrounding area, particularly AstVs in summer with the swimmer crowd. All these data imply that sewage discharge and swimmers co-contribute to the viral occurrence in a seasonal pattern, with the former being more focused in warm seasons (spring and autumn) and the latter in hot seasons (summer). These results indicate that sewage discharge and crowd swimmers, as unsafe swimming conditions, should be avoided to improve public health at the bathing beaches.

Traditional microbe indicators including total bacteria, total coliforms, fecal coliforms, Escherichia coli, enterococci, and F+ coliphage are all frequently used to characterize the microbial contamination state of water bodies for their correlation with pathogenic bacteria. However, these indicators have a poor relationship with viruses, which pose serious threat to economic and human health. Alternative indicators such as bacteroidales may be suitable complementary alternatives to traditional microbe indicators and are being increasingly reported. In the present study, water was analyzed for selected sites along Haihe River in Tianjin for traditional indicators, an alternative indicator (bacteroidales), pathogenic bacteria (Salmonella, Escherichia coli (E. coli) O157:H7, and Vibrio parahaemolyticus), viruses (enteric adenovirus, norovirus, enterovirus, poliovirus and rotavirus), and physicochemical parameters. Results indicated that traditional microbe indicators detected in this study showed good correlation with pathogenic bacteria, and the alternative indicator (bacteroidales) had a surprisingly good relationship with viral presence. We propose that bacteroidales might be a suitable complementary indicator for viral contamination in water bodies.

Antibiotic resistance genes (ARGs) have gained global attention due to their public health threat. Extracelluar ARGs (eARGs) can result in the dissemination of antibiotic resistance via free-living ARGs in natural environments, where they promote ARB transmission in drinking water distribution systems. However, eARG pollution in tap water has not been well researched. In this study, concentrations of eARGs and intracellular ARGs (iARGs) in tap water, sampled at Tianjin, China, were investigated for one year. Fourteen eARG types were found at the highest concentration of 1.3 × 105 gene copies (GC)/L. TetC was detected in 66.7% of samples, followed by sul1, sul2, and qnrA with the same detection frequency of 41.7%. Fifteen iARGs (including tetA, tetB, tetM, tetQ, tetX, sul1, sul2, sul3, ermB, blaTEM, and qnrA) were continuously detected in all collected tap water samples with sul1 and sul2 the most abundant. Additionally, both eARG and iARG concentrations in tap water presented a seasonal pattern with most abundant prevalence in summer. The concentration of observed intracellular sulfonamide resistance genes showed a significantly positive correlation with total nitrogen concentrations. This study suggested that eARG and iARG pollution of drinking water systems pose a potential risk to human public health.