Detection of Rotavirus Vaccine Strains in Oysters and Sewage and Their Relationship with the Gastroenteritis Epidemic.

Rotavirus is one of the major causes of infectious gastroenteritis among infants and children, and live attenuated vaccines for rotavirus A (RVA), namely, Rotarix and RotaTeq, have recently become available in Japan. Rotavirus is known to be excreted from patients and accumulated in oysters similar to norovirus; however, the vaccine strains in aquatic environments or oysters have not yet been analyzed. In this study, we focused on wild-type RVA, which is highly important in considering the risk of infectious diseases. We quantified total RVA, Rotarix, and RotaTeq strains in oyster and sewage samples collected between September 2014 and July 2016 to assess the contamination levels of wild-type RVA by subtracting the quantitative value of rotavirus vaccine strains from that of total RVA. The positive rates of wild-type RVA, Rotarix, and RotaTeq in oysters were 54, 14, and 31%, respectively. These rates were comparable to those of wild-type RVA (57%) and RotaTeq (35%) in sewage; however, Rotarix was not detected in any sewage samples. The comparison of viral concentrations in oysters and sewage suggested more efficient accumulation of the vaccine strains in oysters than the wild-type RVA. The concentration of wild-type RVA in oysters was significantly correlated with that in sewage with a lag time of -6 to 0 weeks which is required for viral transportation from wastewater treatment plants to oysters. On the other hand, no significant correlation was observed between wild-type RVA concentration in sewage and the number of rotavirus-associated gastroenteritis cases, implying the existence of asymptomatic RVA-infected individuals.IMPORTANCE We quantified rotavirus A (RVA), Rotarix, and RotaTeq strains in oyster and sewage samples during two gastroenteritis seasons and revealed the exact contamination of wild-type RVA by subtracting the quantitative value of rotavirus vaccine strains from that of RVA. The concentration of wild-type RVA was significantly correlated between oysters and sewage, although no significant correlation was seen between wild-type RVA concentration in sewage and the number of rotavirus-associated gastroenteritis cases. This finding suggested the existence of asymptomatic patients and that monitoring of rotavirus vaccine strain could be useful to understand the trend of wild-type RVA and rotavirus outbreak in detail. We believe that our study makes a significant contribution to the literature because it reports the detection of rotavirus vaccine strains in oysters.

Enhancement of sunlight irradiation for wastewater disinfection by mixing with seawater.

There is a need for developing a simple and easy-to-maintain disinfection technique for sewage treatment for use in developing countries and disaster-affected areas. We propose a novel disinfection technology that inactivates bacteria in wastewater via sunlight irradiation under high salt concentration by mixing with seawater. The disinfection efficiency of the proposed method was quantitatively evaluated and examined using fecal indicator bacteria. When the salinity in wastewater was adjusted to 30 practical salinity units by mixing with seawater, the constant of inactivation irradiation energy Ks (m2/MJ) was 1.6-2.2-fold greater than that without seawater for total coliforms and Escherichia coli. By contrast, although enterococci were inactivated by sunlight irradiation, an increase in salinity did not enhance disinfection. On setting the irradiation energy of sunlight to 5.5 MJ/m2, >99% of the fecal indicator bacteria were inactivated. Finally, we examined the relationship between the attenuation of irradiance and water depth and accordingly proposed a design of a treatment system wherein wastewater and seawater were adequately mixed and passed via a disinfection tank under the natural flow with sunlight irradiation.

Identification of Enterococcus faecium and Enterococcus faecalis as vanC-type Vancomycin-Resistant Enterococci (VRE) from sewage and river water in the provincial city of Miyazaki, Japan.

As a first step for assessing the risk to human health posed by vancomycin-resistant enterococci (VRE) in the aquatic environment, we screened sewage and urban river water samples from Miyazaki, Japan for VRE. Because vancomycin-resistant organisms are not as prevalent in sewage and river water as vancomycin-susceptible organisms, the samples were screened by minimum inhibitory concentration test using the vancomycin-supplemented membrane-Enterococcus indoxyl-ß-d-glucoside (mEI) agar. The isolates, presumed to be enterococci, were identified using 16S rRNA sequencing analysis. The percentages of VRE isolates screened using 4 µg mL(-1) vancomycin-supplemented mEI agar from sewage and urban river water samples were 12% and 24%, respectively. The vancomycin-resistant genes vanC1 and vanC2/3 were detected in the isolates from both samples by PCR analysis. All enterococci isolates containing vanC1, which is a specific gene for vanC-type of VRE, were identified as Enterococcus casseliflavus/gallinarum. Further, 92% enterococci isolates containing vanC2/3 were identified as E. casseliflavus/gallinarum, the remaining isolates containing vanC2/3 were E. faecium (4%) and E. faecalis (4%). Thereafter, the distribution of E. faecium and E. faecalis, which are the major types of enterococci in humans containing vanC2/3, was observed in the water samples collected.

Significant Factors for Modelling Survival of Escherichia coli in Lake Sediments.

Currently available numerical models that describe the fecal contamination of aquatic environments using Escherichia coli as an indicator bacterium did not consider its survival in sediments. We conducted a series of comparative experiments to reveal the independent and interactive effects of sediment factors, including temperature, pH, water-extractable total dissolved solids (TDSs), coexisting microbes, and sampling sites, in lake environments on E. coli survival. In experiments, E. coli survival was observed by controlling any two factors at a time. Consequently, the decrease in pH and presence of coexisting microbes enhanced E. coli die-off, whereas the addition of water-extractable TDSs promoted its growth. To select factors to be considered for modelling E. coli survival in sediments, the independent effects of each factor and the interaction effect of the two factors were statistically compared based on their effect sizes (η2). As a result, pH (η2 = 59.5-89.0%) affected E. coli survival most significantly, followed by coexisting microbes (1.7-48.4%). Among the interactions affecting E. coli survival, including pH or coexisting microbes-which had larger independent effects-relatively larger statistically significant interactions were observed between pH and coexisting microbes (31.1%), coexisting microbes and water-extractable TDSs (85.4%), and coexisting microbes and temperature (26.4%).

Comparative experiment to select water quality parameters for modelling the survival of Escherichia coli in lakes.

Numerical health risk assessment models have been developed to describe faecal contamination of water using Escherichia coli as an indicator bacterium. Although many previously established numerical models for E. coli in aquatic environments have only considered the effects of one or two water quality parameters such as temperature and sunlight, it is difficult to simulate E. coli survival with only one or two parameters because the aquatic environment is a complex system. This study conducted a series of comparative experiments to select water quality parameters that should be preferentially considered in a numerical model for E. coli survival in lakes. The parameters considered were temperature, pH, dissolved oxygen (DO), total dissolved solids (TDS), suspended solids (SS), coexisting microbes, and light intensity. In the laboratory experiments, the survival of E. coli was observed by controlling two of these seven parameters, and the effects of these parameters on the rate of E. coli population change were statistically compared. Consequently, light intensity affected the survival of E. coli most significantly, followed by the presence of coexisting microbes, temperature, pH, and TDS. However, DO and SS had smaller effects on survival than other parameters. High-impact interactions on E. coli survival were observed between temperature and TDS and temperature and coexisting microbes. These results suggest that existing numerical models for simulating E. coli survival in lakes should be modified to consider the independent and interactive effects of multiple parameters such as sunlight, coexisting microbes, temperature, pH, and TDS.

Impact of nCuO containing treated wastewater on soil microbes and dissolved organic matter in paddy field leachate.

Using treated wastewater (TWW) resources in agriculture is a major pathway for disseminating nanoparticles. Copper-oxide nanoparticles (nCuO) offer potential benefits, but their presence in the environment poses risks to agricultural and environmental sustainability. This study examined soil microbial transformations and the composition of leachate dissolved organic matter (DOM) of paddy soils irrigated with nCuO-contaminated TWW at different concentrations (T2: 0.02 mgL-1, T3: 0.2 mgL-1, T4: 2.0 mgL-1) and examined the differences in Cu source (T5: 0.2 mgL-1 CuSO4). Results showed negative impacts on the absolute microbial abundance with up to 46 % reduction relative to the control treatment (T1). Changes in relative abundance of specific microbes at the genus level deviated from the corresponding phyla. Acidobacteria, Actinobacteria, Chloroflexi, and Verrucomicrobia phyla increased in the surface (0-3 cm) and subsurface (3-15 cm) layers responding differently to nCuO. In the 0-3 cm layer, Nitrospirae, Euryarchaeota, and Crenarchaeota increased, but only Dechloromonas genus from Proteobacteria increased with increasing nCuO. No significant variations were observed in the DOM composition, except in T4, which had a significantly low content of dissolved organic carbon (DOC), total dissolved nitrogen, and terrestrial humic-like and protein-like components. Ninety-eight distinct genera were identified, of which 44%, including 15 bacteria and two archaea, varied between the surface and subsurface, among treatments, and significantly correlated with more DOM parameters in the subsurface. T4 had the highest microbial diversity in the 0-3 layer, and Cu treatments slightly increased the diversity index in the subsurface. Moreover, the effects differed by Cu source, with T3 showing 10 % more reduction in the subsurface and 17 % less reduction in the surface than T5. The variable microbial responses to nCuO and their strong correlations with DOM highlight the need to consider the potential consequences of low nCuO concentrations on biogeochemical cycles.

Tracing the pathways by which flood duration impacts soil bacteria through soil properties and water-extractable dissolved organic matter: A soil column experiment.

Soil microbial communities control biogeochemical processes, nutrient cycling, and organic carbon storage and release in wetlands, which are influenced by flooding. To predict soil nutrient function in wetland ecosystems, understanding the effect of flooding on soil biogeochemical cycling and energy flux, including soil properties, dissolved organic matter (DOM), and microbial communities is essential. This study investigated how different flood durations (1, 3, 8, 16, and 30 d) affect the interactions between physicochemical properties and bacterial communities in a river wetland. The DOM composition was measured using ultraviolet/visible spectrophotometry coupled with fluorescence spectroscopy, and the bacterial communities were identified using 16S rRNA sequencing. Simpson's diversity index varied from 0.92 to 0.94, indicating high bacterial diversity throughout the treatments; the highest and lowest bacterial diversities were found at 1 and 8 flooding days, respectively. The abundance of Desulturomonadales, Clostridiales, Bacteroidales, and Gaiellales was positively correlated with pH, electrical conductivity, water-extractable dissolved organic carbon (WEOC), and water-extractable total dissolved nitrogen (TDN) but negatively correlated with dissolved oxygen (DO) and soil organic matter (SOM), suggesting complex interactions among these factors in response to flooding. Structural equation model revealed that flooding directly increased TDN but indirectly increased WEOC through increasing soil pH; and directly decreased DO and SOM, leading to decreases in total protein-like fraction. Three significant pathways were identified, showing the impacts of flooding on bacterial diversity: (1) flood duration decreased DO, resulting in decreased bacterial diversity; (2) flood duration decreased SOM, leading to increased bacterial diversity; and (3) flood duration decreased DO and SOM, leading to increased bacterial diversity via decreased total protein-like fraction. This study indicated that prolonged flooding has both positive and negative impacts on bacterial diversity, depending on environmental factors. It highlights the importance of flooding in shaping soil bacterial communities, with implications for nutrient cycling and carbon storage in wetlands.

Characterization of extended-spectrum ß-lactamase-producing Escherichia coli isolated from municipal and hospital wastewater in Japan.

OBJECTIVES: The purpose of this study was to characterize the strains of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (ESBL-EC) isolated from municipal and hospital wastewater by detecting antibiotic resistance genes (ARGs) as well as antibiotic susceptibility. To identify the source of ESBL-EC, multi-locus sequence typing and typing plasmids that may carry ESBL-producing genes were conducted. METHODS: Wastewater was sampled twice a month from February 2019 to February 2020 from a municipal wastewater treatment plant and hospital located in a city in northeastern Japan. Throughout the study period, 279 and 37 strains of ESBL-EC were isolated from municipal and hospital wastewater, respectively. RESULTS: All 316 isolates were resistant to ampicillin and cefotaxime and susceptible to imipenem and tigecycline. Almost all (98.1%) of the ESBL-EC isolates possessed blaCTX-M, and the blaCTX-M-9 group was detected most frequently (62.3%). Multi-locus sequence typing revealed a higher diversity of sequence types (STs) in the isolates from municipal wastewater than in those from hospital wastewater; although ST131, which recently caused nosocomial- and community-associated infections worldwide, was dominant in both types of wastewater. All ST131 isolates possessed the IncFII plasmid, which is often reported to carry blaCTX-M. CONCLUSIONS: These results demonstrated that healthy people carry clinically important antibiotic-resistant bacteria and ARGs, motivating routine monitoring of municipal wastewater to detect such antibiotic-resistant bacteria and ARGs from a variety of sources supported by the high diversity of STs in the present study.

Review of Antimicrobial Resistance in Wastewater in Japan: Current Challenges and Future Perspectives.

Antimicrobial resistance (AMR) circulates through humans, animals, and the environments, requiring a One Health approach. Recently, urban sewage has increasingly been suggested as a hotspot for AMR even in high-income countries (HICs), where the water sanitation and hygiene infrastructure are well-developed. To understand the current status of AMR in wastewater in a HIC, we reviewed the epidemiological studies on AMR in the sewage environment in Japan from the published literature. Our review showed that a wide variety of clinically important antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs), and antimicrobial residues are present in human wastewater in Japan. Their concentrations are lower than in low- and middle-income countries (LMICs) and are further reduced by sewage treatment plants (STPs) before discharge. Nevertheless, the remaining ARB and ARGs could be an important source of AMR contamination in river water. Furthermore, hospital effluence may be an important reservoir of clinically important ARB. The high concentration of antimicrobial agents commonly prescribed in Japan may contribute to the selection and dissemination of AMR within wastewater. Our review shows the importance of both monitoring for AMR and antimicrobials in human wastewater and efforts to reduce their contamination load in wastewater.

Detection and genetic analysis of Escherichia coli from Tonle Sap Lake and its tributaries in Cambodia: Spatial distribution, seasonal variation, pathogenicity, and antimicrobial resistance.

As an indicator of fecal contamination, Escherichia coli was monitored in Tonle Sap Lake, Cambodia, and its tributaries during low- and high-water seasons, focusing on the impacts on floating villagers inhabiting boathouses. E. coli concentrations in the floating villages (3.6 × 103 and 5.7 × 103 CFU/100 mL during the low- and high-water seasons, respectively) were significantly higher than those in other lake sites (4.0 × 101 and 7.0 × 100 CFU/100 mL during the low- and high-water seasons, respectively) and rivers (3.3 × 102 and 8.9 × 102 CFU/100 mL during the low- and high-water seasons, respectively), most likely because fecal materials from the boathouses were discharged without treatment. At most of the lake sampling sites remote from the boathouses, the E. coli concentration was lower during the high-water season than that during the low-water season, due to dilution by lake water. E. coli colonies detected during monitoring were isolated for pathotyping, antimicrobial susceptibility testing, beta-lactamase gene detection, and multilocus sequencing typing (MLST). Of the 659 E. coli isolates, 101 (15.3%) were diarrheagenic E. coli (DEC). The prevalence of DEC (52.2%) in the floating villages during the low-water season was higher than that during the high-water season (4.2%) and that in other sites during both seasons (10.6-21.3%). The DEC isolates from the floating villages during the low-water season showed high antimicrobial resistance, including ampicillin (83.4%) and ciprofloxacin (83.4%), and frequently possessed a beta-lactamase gene (blaTEM) (83.4%). MLST analysis indicated that the predominant sequence type (ST) of DEC isolates from the floating villages possibly originated from humans, whereas more diverse STs were detected in isolates from other sites. We revealed the wide presence of diarrheagenic and antimicrobial-resistant E. coli in Tonle Sap Lake and identified a considerable infection risk in floating villages, especially during the low-water season.

Antibiotic-resistant Escherichia coli isolated from dairy cows and their surrounding environment on a livestock farm practicing prudent antimicrobial use.

On a livestock farm where antimicrobial administration and its history had been managed for prudent use of antimicrobials, we surveyed antibiotic-resistant Escherichia coli strains isolated from cow feces and the surrounding environment (i.e., rat and crow feces, and water samples from a drainage pit and wastewater processing tank) every month for 1 year. Two strains (1.7%) in cow feces were resistant to tetracycline, whereas all other strains were susceptible to all other antimicrobials. Among 136 strains isolated from cows and wild animals, only one ampicillin-resistant strain was identified. The antibiotic resistance rate in the drainage from the barn was 8.3% (10/120), and all strains showed susceptibility for 8 months of the year. Tetracycline resistance was common in all resistant strains isolated from animal feces and water samples; all tetracycline-resistant strains carried tetA. These results strongly support the proper use and management of antibiotics on farms to minimize the outbreak and spread of antibiotic-resistant bacteria.

Comparison of Antibiotic Resistance Profile of Escherichia coli between Pristine and Human-Impacted Sites in a River.

Information on the actual existence of antibiotic-resistant bacteria in rivers where sewage, urban wastewater, and livestock wastewater do not load is essential to prevent the spread of antibiotic-resistant bacteria in water environments. This study compared the antibiotic resistance profile of Escherichia coli upstream and downstream of human habitation. The survey was conducted in the summer, winter, and spring seasons. Resistance to one or more antibiotics at upstream and downstream sites was on average 18% and 20%, respectively, and no significant difference was observed between the survey sites. The resistance rates at the upstream site (total of 98 isolated strains) to each antibiotic were cefazolin 17%, tetracycline 12%, and ampicillin 8%, in descending order. Conversely, for the downstream site (total of 89 isolated strains), the rates were ampicillin 16%, cefazolin 16%, and tetracycline 1% in descending order. The resistance rate of tetracycline in the downstream site was significantly lower than that of the upstream site. Furthermore, phylogenetic analysis revealed that many strains showed different resistance profiles even in the same cluster of the Pulsed-Field Gel Electrophoresis (PFGE) pattern. Moreover, the resistance profiles differed in the same cluster of the upstream and the downstream sites. In flowing from the upstream to the downstream site, it is plausible that E. coli transmitted or lacked the antibiotic resistance gene.

Prevalence of Antibiotic-Resistant Bacteria ESKAPE among Healthy People Estimated by Monitoring of Municipal Wastewater.

There is increasing attention toward factors that potentially contribute to antibiotic resistance (AR), as well as an interest in exploring the emergence and occurrence of antibiotic resistance bacteria (ARB). We monitored six ARBs that cause hospital outbreaks in wastewater influent to highlight the presence of these ARBs in the general population. We analyzed wastewater samples from a municipal wastewater treatment plant (MWWTP) and hospital wastewater (HW) for six species of ARB: Carbapenem-resistant Enterobacteria (CARBA), extended-spectrum ß-lactamase producing Enterobacteria (ESBL), multidrug-resistant Acinetobacter (MDRA), multidrug-resistant Pseudomonas aeruginosa (MDRP), methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococci (VRE). We registered a high percentage of ARBs in MWWTP samples (>66%) for all ARBs except for MDRP, indicating a high prevalence in the population. Percentages in HW samples were low (<78%), and no VRE was detected throughout the study. CARBA and ESBL were detected in all wastewater samples, whereas MDRA and MRSA had a high abundance. This result demonstrated the functionality of using raw wastewater at MWWTP to monitor the presence and extent of ARB in healthy populations. This kind of surveillance will contribute to strengthening the efforts toward reducing ARBs through the detection of ARBs to which the general population is exposed.

Methane mitigation is associated with reduced abundance of methanogenic and methanotrophic communities in paddy soils continuously sub-irrigated with treated wastewater.

Herein, we examined emissions of CH4 and the community structures of methanogenic archaea and methanotrophic bacteria in paddy soils subjected to a novel irrigation system, namely continuous sub-irrigation with treated wastewater (TWW). This system has recently been developed by our group to effectively reuse TWW for the cultivation of protein-rich rice. The results showed that, despite not using mineral fertilisers, the wastewater reuse system produced a rice yield comparable to that of a conventional cultivation practice and reduced CH4 emissions from paddy fields by 80%. Continuous sub-irrigation with TWW significantly inhibited the growth of methanogens in the lower soil layer during the reproductive stage of rice plants, which was strongly consistent with the effective CH4 mitigation, resulting in a vast reduction in the abundance of methanotrophs in the upper soil layer. The compositions of the examined microbial communities were not particularly affected by the studied cultivation practices. Overall, this study demonstrated that continuous sub-irrigation with TWW was an effective method to produce high rice yield and simultaneously reduce CH4 emissions from paddy fields, and it also highlighted the potential underlying microbial mechanisms of the greenhouse gas mitigation.

Tracking Fecal Bacterial Dispersion from Municipal Wastewater to Peri-Urban Farms during Monsoon Rains in Hue City, Vietnam.

Disease outbreaks attributed to monsoon flood-induced pathogen exposure are frequently reported, especially in developing cities with poor sanitation. Contamination levels have been monitored in past studies, yet the sources, routes, and extents of contamination are not always clear. We evaluated pollution from municipal wastewater (MWW) discharge and investigated fecal contamination by Escherichia coli (E. coli) in three agricultural fields on the outskirts of Hue City, Vietnam. After E. coli concentration was determined in irrigation water (IRW), MWW, soil, vegetables (VEG), and manure, its dispersion from MWW was tracked using multilocus sequence typing (MLST) and phylogenetic analyses during the wet and dry seasons. IRW was severely contaminated; 94% of the samples were positive with E. coli exceeding the stipulated standards, while VEG contamination was very low in both seasons. The confirmed total number of isolates was comparable between the seasons; however, results from MLST and phylogenetic clustering revealed more links between the sites and samples to MWW during the wet season. The wet season had four mixed clusters of E. coli isolates from multiple locations and samples linked to MWW, while only one mixed cluster also linking MWW to IRW was observed during the dry season. The most prevalent sequence type (ST) complex 10 and two others (40 and 155) have been associated with disease outbreaks, while other STs have links to major pathotypes. Irrigation canals are significant routes for E. coli dispersion through direct links to the urban drainage-infested river. This study clarified the genotype of E. coli in Hue city, and the numerous links between the samples and sites revealed MWW discharge as the source of E. coli contamination that was enhanced by flooding.

Growth and antibiotic resistance acquisition of Escherichia coli in a river that receives treated sewage effluent.

Wastewater treatment plants could discharge Escherichia coli and antibiotic resistant bacteria to the environment adjacent to, or downstream of their discharge point. However, their discharge also contains nutrients which could promote growth of E. coli in water environments. This study was done to clarify the potential of growth and antibiotic resistance acquisition of E. coli in a river environment. Levels of E. coli were monitored in a river that receives treated sewage effluent for over four years. River water, periphyton and sediment samples were collected at sites upstream and downstream of treated sewage inflow. Concentrations of E. coli increased in river water and periphyton at the sites downstream of the treated sewage inflow, although levels of E. coli were very low or below detection limit in the treated sewage samples. Concentrations of Chlorophyll a increased at the downstream sites, likely due to nutrient input from the treated sewage. Based on pulsed field gel electrophoresis, identical genotype occurred at multiple sites both upstream and downstream of the treated sewage inflow. However, strains resistant to antibiotics such as ampicillin, cefazolin, ciprofloxacin, and chloramphenicol were more frequently obtained from the downstream sites than the upstream sites. Multidrug resistant E. coli strains were detected in periphyton and sediment samples collected at the downstream sites. Non-resistant strains with PDGE genotype identical to the multi-drug strains were also detected, indicating that E. coli might have become resistant to antibiotics by acquiring resistance genes via horizontal gene transfer. Laboratory incubation experiment showed the growth of E. coli in periphyton or sediment-fed river water samples. These results suggest that the wastewater treatment inflow did not directly provide E. coli to the river water, but could promote the growth of periphyton, which could lead to the elevated levels of E. coli and the emergence of antibiotic resistant E. coli.

Weekly Variation of Rotavirus A Concentrations in Sewage and Oysters in Japan, 2014-2016.

Concentrations of rotavirus A, in sewage and oysters collected weekly from September 2014 to April 2016 in Japan, were investigated using RT-qPCR; results showed up to 6.5 log10 copies/mL and 4.3 log10 copies/g of digestive tissue (DT) in sewage and oysters, respectively. No correlation was found between rotavirus concentration in sewage and oysters and cases of rotavirus-associated gastroenteritis.

Temporal Variabilities in Genetic Patterns and Antibiotic Resistance Profiles of Enterococci Isolated from Human Feces.

Temporal variabilities in the genetic patterns and antibiotic resistance profiles of enterococci were monitored over a 7-month period. Enterococcus faecalis isolates (103 strains) collected from feces showed only one genetic pattern and antibiotic resistance profile within 0 d and 30 d. In contrast, after 60 d and 90 d, the genetic patterns and antibiotic resistance profiles of all E. faecalis isolates (8 strains) clearly differed within 30 d. These results indicate that the genetic patterns and antibiotic resistance profiles of E. faecalis in human feces changed to completely dissimilar patterns between 1 and 2 months.

Concentration of MS2 phage in river water by a combined ferric colloid adsorption and foam separation-based method, with MS2 phage leaching from ferric colloid.

The concentration of MS2 phage as a model RNA virus in river water using a combined ferric colloid adsorption and foam separation-based method was examined. The MS2 phage concentrations were determined by the plaque-forming unit (PFU) method and reverse transcription quantitative PCR (RT-qPCR) analysis. When ferric colloid adsorption was performed prior to foam separation, MS2 phage was effectively removed from river water and concentrated in the generated foam within 7 min. The removal efficiency was >99% at the optimum iron and casein concentrations of 5 mg-Fe/L and 10 mg/L, respectively. Furthermore, based on the analysis of the collected ferric colloid dissolved using deferoxamine, the MS2 concentration in the colloid-dissolved solution was 190-fold higher than that found in raw water according to RT-qPCR analysis. This is a novel method for concentrating RNA viruses to facilitate their detection in river water using coagulation and foam separation combined with chelate dissolution of ferric flocs.

Susceptibility of Pseudomonas aeruginosa isolates collected from river water in Japan to antipseudomonal agents.

Pseudomonas aeruginosa is responsible for a number of opportunistic and nosocomial infections. However, very little information is available on the ecology of P. aeruginosa in water environments and its association with antimicrobial resistance. In this study, the distribution of P. aeruginosa and the resistance of P. aeruginosa isolates to various antibiotics were investigated from two rivers, Kiyotake and Yae that flow through Miyazaki City, Japan. P. aeruginosa was distributed widely along the river basins with counts ranging from 2-46 cfu/100 mL. The susceptibility of P. aeruginosa isolates collected from the rivers to various antibiotics was examined by minimum inhibitory concentration. Multidrug-resistant P. aeruginosa strains were not observed or isolated from either river. However, one piperacillin-resistant P. aeruginosa was detected among a total of 516 isolates, and this isolate was also resistant to cefotaxime and showed intermediate resistance to cefitazidime. Less than 1% of all isolates (n=5) were resistant to imipenem, which is the most effective antibiotic against both Gram-negative and Gram-positive bacteria. However, all P. aeruginosa isolates were completely resistant to tetracyclines, which are the most commonly prescribed antibiotics. In advanced nations such as Japan where the majority of the population is urban and where medical services are widespread, antibiotic-resistant bacteria such as P. aeruginosa are likely to be widely distributed, even in apparently pristine rivers.