Studying the ecological risk of antibiotic resistance genes (ARGs) to wild animals from human disturbance (HD) is an important aspect of \"One Health\". The highest risk level of ARGs is reflected in pathogenic antibiotic-resistant bacteria (PARBs). Metagenomics was used to analyze the characteristics of PARBs in river sediments. Then, the total contribution of ARGs and virulence factors (VFs) were assessed to determine the health risk of PARBs to the rivers. Results showed that HD increased the diversity and total relative abundance of ARG groups, as well as increased the kinds of PARBs, their total relative abundance, and their gene numbers of ARGs and VFs. The total health risks of PARBs in wild habitat group (CK group), agriculture group (WA group), grazing group (WG group), and domestic sewage group (WS group) were 0.067 × 10-3, -1.55 × 10-3, 87.93 × 10-3, and 153.53 × 10-3, respectively. Grazing and domestic sewage increased the health risk of PARBs. However, agriculture did not increase the total health risk of the rivers, but agriculture also introduced new pathogenic mechanisms and increased the range of drug resistance. More serious was the increased transfer risk of ARGs in the PARBs from the rivers to wild animals under agriculture and grazing. If the ARGs in the PARBs are transferred from the rivers under HD to wild animals, then wild animals may face severe challenges of acquiring new pathogenic mechanisms and developing resistance to antibiotics. Further analysis showed that the total phosphorus (TP) and dissolved organic nitrogen (DON) were related to the risk of ARGs. Therefore, controlling human emissions of TP and DON could reduce the health risk of rivers.

Perfluoroalkyl substances (PFASs) and antibiotic resistance genes (ARGs) in drinking water are environmental issues that require special attention. The objective of this study was to know the effects of PFASs on microbial communities and their functional genes from source water to tap water. PFASs were detected by mass-labeled internal standards method, and the microbial communities and functional genes were analyzed by metagenomics. Our results indicated that the concentration of total PFASs in the water ranged from 47.7 to 171.4 ng/L, with perfluorobutanoic acid (PFBA) and perfluorooctanoic acid (PFOA) being the dominant types. The PFASs concentration decreased slowly from source to tap water in some months. PFBA, PFOA, perfluorooctane sulfonic acid (PFOS) and perfluorohexanoic acid (PFHxA) influenced the functional genes related to two-component system, bacterial secretion system and flagellar assembly of Aquabacterium, Methylobacterium, and Curvibacter, which contributed significantly to macB and evgS. Therefore, the bacterial communities enhanced adaptation to fluctuating environments by upregulating some functional genes under the PFASs stress, with concomitant changes in the expression of ARGs. Moreover, PFASs also promoted the expression of functional genes associated with human diseases, such as shigellosis and tuberculosis, which increased the risk of human pathogenicity. The bench scale experiment results also suggested that PFOA and PFOS in drinking water can promote the ARGs proliferation and induce microbial risk. Therefore, it is necessary to take measures to prevent the risks caused by PFASs and ARGs in drinking water.

Secondary water supply systems (SWSSs) are widely used to supply water to high-rise households in urban residential buildings. A special mode of double tanks with one used while another was spared was noted in SWSSs, which would facilitate microbial growth due to longer water stagnation in the spare tank. There are limited studies on the microbial risk of water samples in such SWSSs. In this study, the input water valves of the operational SWSSs consisting of double tanks were artificially closed and opened on time. Propidium monoazide-qPCR and high-throughput sequencing were performed to systematically investigate the microbial risks in water samples. After closing the tank input water valve, it may take several weeks to replace the bulk water in the spare tank. The residual chlorine concentration in the spare tank decreased by up to 85 % within 2-3 days compared with that in the input water. The microbial communities in the spare and used tank water samples clustered separately. High bacterial 16S rRNA gene abundance and pathogens-like sequences were detected in the spare tanks. Most antibiotic-resistant genes (11/15) in the spare tanks showed an increase in their relative abundance. Moreover, when both tanks within one SWSS were in use, the water quality of the used tank water samples deteriorated to varying degrees. Overall, running SWSSs with double tanks will reduce the replacement rate of water in one storage tank, and consumers who use taps served by the presented SWSSs may have a higher microbial risk.

Swimming pools adopt chlorination to ensure microbial safety. Giardia has attracted attention in swimming pool water because of its occurrence, pathogenicity, and chlorine resistance. To control Giardia concentrations in pool water and reduce the microbial risk, higher chlorine doses are required during disinfection. Unfortunately, this process produces carcinogenic disinfection byproducts that increase the risk of chemical exposure. Therefore, quantitatively evaluating the comparative microbial vs. chemical exposure risks that stem from chlorination inactivation of Giardia in swimming pool water is an issue that demands attention. We simulated an indoor swimming pool disinfection scenario that followed common real-world disinfection practices. A quantitative microbial risk assessment coupled with a chemical exposure risk assessment was employed to compare the Giardia microbial exposure risk (MER) and the trihalomethane chemical exposure risk (CER) to humans. The results demonstrated a 22% decrease in MER- and CER-induced health exposure risk, from 8.45E-5 at 8:00 to 6.60E-5 at 19:00. Both the MER and CER decreased gradually, dropping to 3.26E-5 and 3.35E-5 at 19:00, respectively. However, the CER exceeded the MER after 18:30 and became the dominant factor affecting the total exposure risk. Past the 18 hr mark, the contribution of trihalomethane CER far exceeded the risk aversion from microbial inactivation, leading to a net increase in total exposure risk despite the declining MER. Swimmers may consider swimming after 19:00, when the total exposure risk is the lowest. Lowering water temperature and/or pH were identified as the most sensitive factors to minimize the overall health exposure risk.

Fresh vegetables are considered as a reservoir of pathogenic bacteria and antibiotic resistance genes (ARGs), which are the emerging environmental contaminants, posing increasing concerned risk to human health. However, the prevalence of pathogens in phyllosphere of fresh vegetables, as well as the association of ARGs with pathogenic bacteria, have not been well elaborated. In this study, we explored the structure of microbial communities and ARGs through high-throughput quantitative PCR and 16S rRNA gene Illumina sequencing, and characterized the microorganisms resisting to antibiotics by pure culture. From phyllosphere of six different kinds of vegetables, 205 ARGs were detected and genes for multidrug resistance was the most abundant. The predominant potential pathogens were classified to Pseudomonas, Klebsiella, and Acinetobacter genera, which carried various ARGs such as multidrug and beta-lactam resistance genes presumedly. Among six kinds of vegetables, Lactuca sativa var. asparagina carried the highest abundance of potential pathogens and ARGs, while Allium sativum L harbored the lowest abundance of pathogens and ARGs. In addition, various culturable bacteria resisting to colistin or meropenem could be isolated from all vegetables, remarkably, all the isolates resistant to both antibiotics are potential pathogens. Our study highlighted the risks of pathogens and ARGs from raw vegetables to consumers, characterized their structure patterns among different vegetables, and analyzed the potential mechanisms regulating phyllosphere pathogens and resistome of fresh vegetables, which would be helpful for reducing the microbial risk from vegetable ingestion.

Secondary water supply systems (SWSSs) are characterized by long water stagnation and low levels of chlorine residuals, which may pose a high microbial risk to terminal users. In this study, the SWSSs of 12 residential neighborhoods in a metropolitan area of 5 million people in southeastern China were seasonally investigated to assess their microbial risks by determining more than 30 physicochemical and biological parameters. Although the microbiological quality of SWSS water met the requirements of the standards for drinking water quality of China, it did deteriorate in various aspects. The heterotrophic plate counts with R2A media were high (> 100 CFU/mL) in some SWSS tank and tap water samples. Propidium monoazide (PMA)-qPCR revealed a one magnitude higher abundance of viable bacteria in the tank and tap water samples (average 103.63±1.10 and 103.65±1.25 gene copies/mL, respectively) compared with the input water samples, and Enterococcus, Acanthamoeba, and Hartmannella vermiformis were only detected in the tanks. In particular, the high detection frequency of Legionella in 35% tank and 21% tap water samples suggested it is a supplementary microbial safety indicator in SWSSs. The microbial regrowth potential was more obvious in summer, and Illumina sequencing also demonstrated distinct seasonal changes in the relative abundance of bacterial gene sequences at the genus level. Turbidity and residual chlorine were closely connected with total bacterial biomass, and the latter seemed responsible for microbial community structure alteration. The extremely low chlorine residuals associated with a high abundance of total bacteria (as high as 106.48 gene copies/mL) and Legionella (as high as 106.71 gene copies/100 mL) in the closed valve tanks highlighted the high microbial risk increased by mishandling the operation of SWSSs. This study found that SWSSs possessed a higher microbial risk than the drinking water network, which suggested that the frequency and scope of monitoring the microbial risk of SWSSs in megacities should be strengthened for the purpose of waterborne epidemic disease prevention and control.

The epidemic of COVID-19 has aroused people\'s particular attention to biosafety. A growing number of disinfection products have been consumed during this period. However, the flaw of disinfection has not received enough attention, especially in water treatment processes. While cutting down the quantity of microorganisms, disinfection processes exert a considerable selection effect on bacteria and thus reshape the microbial community structure to a great extent, causing the problem of disinfection-residual-bacteria (DRB). These systematic and profound changes could lead to the shift in regrowth potential, bio fouling potential, as well as antibiotic resistance level and might cause a series of potential risks. In this review, we collected and summarized the data from the literature in recent 10 years about the microbial community structure shifting of natural water or wastewater in full-scale treatment plants caused by disinfection. Based on these data, typical DRB with the most reporting frequency after disinfection by chlorine-containing disinfectants, ozone disinfection, and ultraviolet disinfection were identified and summarized, which were the bacteria with a relative abundance of over 5% in the residual bacteria community and the bacteria with an increasing rate of relative abundance over 100% after disinfection. Furthermore, the phylogenic relationship and potential risks of these typical DRB were also analyzed. Twelve out of fifteen typical DRB genera contain pathogenic strains, and many were reported of great secretion ability. Pseudomonas and Acinetobacter possess multiple disinfection resistance and could be considered as model bacteria in future studies of disinfection. We also discussed the growth, secretion, and antibiotic resistance characteristics of DRB, as well as possible control strategies. The DRB phenomenon is not limited to water treatment but also exists in the air and solid disinfection processes, which need more attention and more profound research, especially in the period of COVID-19.

The key to water reclamation and reuse is water quality safety insurance and risk control. Microbial risk control is an important issue that requires priority during the safe reuse of reclaimed water. This paper systematically summarizes the control requirements for microbial indicators in China\'s current water reuse standards, focusing on the necessity and deficiencies of water quality targets and microbial indicator concentration control. The performance targets based on the removal requirements of microorganisms together with the methodology and implementation strategies are introduced in detail for the first time. In the future, it is necessary to further explore the microbial control method of water reclamation based on the combination of water quality targets and performance targets, which could provide support for the safe reuse of reclaimed water in China.

It remains unclear whether well-maintained subjects, with periodontitis in the past, effectively treated, and maintained for a long time, have the same subgingival microbiome as healthy subjects. Therefore, the objective of this study was to investigate the characteristics of the subgingival microbiome in well-maintained patients with a history of periodontitis compared with healthy subjects.
We recruited in 17 well-maintained individuals (no evidence of clinical inflammation and progress of periodontitis) and 21 healthy individuals. Periodontal clinical parameters, consisting of missing teeth, plaque index (PLI), periodontal depth (PD), and bleeding index (BI), were recorded and analyzed. The pooled subgingival samples from mesiobuccal sites of two maxillary first molars were collected. The V3-V4 region of 16S rRNA gene from 38 subgingival samples was sequenced and analyzed. Alpha diversity, microbial composition, types of bacteria, functional pathways between well-maintained group and health group were compared using Mann-Whitney U test. Spearman correlation was used in analyzing the symbiotic relationship among taxa. A classification model was constructed to distinguish two ecological types.
The maintained individuals demonstrated a different microbiome from healthy subjects, with higher diversity, more disordered structure, more pathogenic microbiota, and more host-destructive metabolism pathways. The genera Actinomyces, Streptococcus, Leptotrichia, Capnocytophaga, Lautropia, and Fusobacterium were predominant components with relative abundance >5% in the subgingival microbiome of well-maintained patients. The classification model by microbiota got a remarkable accuracy of 83.33%.
Individuals with well-maintained periodontitis showed a more dysbiotic microbial community than healthy individuals. Therefore, close monitoring and scheduled maintenance treatment are necessary for them to maintain a healthy periodontal condition.