Efficiency of peracetic acid in inactivating bacteria, viruses, and spores in water determined with ATP bioluminescence, quantitative PCR, and culture-based methods.

The disinfection efficiency of peracetic acid (PAA) was investigated on three microbial types using three different methods (filtration-based ATP (adenosine-triphosphate) bioluminescence, quantitative polymerase chain reaction (qPCR), culture-based method). Fecal indicator bacteria (Enterococcus faecium), virus indicator (male-specific (F(+)) coliphages (coliphages)), and protozoa disinfection surrogate (Bacillus subtilis spores (spores)) were tested. The mode of action for spore disinfection was visualized using scanning electron microscopy. The results indicated that PAA concentrations of 5 ppm (contact time: 5 min), 50 ppm (10 min), and 3,000 ppm (5 min) were needed to achieve 3-log reduction of E. faecium, coliphages, and spores, respectively. Scanning electron microscopy observation showed that PAA targets the external layers of spores. The lower reduction rates of tested microbes measured with qPCR suggest that qPCR may overestimate the surviving microbes. Collectively, PAA showed broad disinfection efficiency (susceptibility: E. faecium > coliphages > spores). For E. faecium and spores, ATP bioluminescence was substantially faster (∼5 min) than culture-based method (>24 h) and qPCR (2-3 h). This study suggests PAA as an effective alternative to inactivate broad types of microbial contaminants in water. Together with the use of rapid detection methods, this approach can be useful for urgent situations when timely response is needed for ensuring water quality.

Fermented Milk Containing Lacticaseibacillus rhamnosus SNU50430 Modulates Immune Responses and Gut Microbiota in Antibiotic-Treated Mice.

Antibiotics are used to control infectious diseases. However, adverse effects of antibiotics, such as devastation of the gut microbiota and enhancement of the inflammatory response, have been reported. Health benefits of fermented milk are established and can be enhanced by the addition of probiotic strains. In this study, we evaluated effects of fermented milk containing Lacticaseibacillus rhamnosus (L. rhamnosus) SNUG50430 in a mouse model with antibiotic treatment. Fermented milk containing 2 × 105 colony-forming units of L. rhamnosus SNUG50430 was administered to six week-old female BALB/c mice for 1 week. Interleukin (IL)-10 levels in colon samples were significantly increased (P < 0.05) compared to water-treated mice, whereas interferon-gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) were decreased, of mice treated with fermented milk containing L. rhamnosus SNUG50430-antibiotics-treated (FM+LR+Abx-treated) mice. Phylum Firmicutes composition in the gut was restored and the relative abundances of several bacteria, including the genera Coprococcus and Lactobacillus, were increased in FM+LR+Abx-treated mice compared to PBS+Abx-treated mice. Interestingly, abundances of genus Coprococcus and Lactobacillus were positively correlated with IL-5 and IL-10 levels (P < 0.05) in colon samples and negative correlated with IFN-γ and TNF-α levels in serum samples (P < 0.001). Acetate and butyrate were increased in mice with fermented milk and fecal microbiota of FM+LR+Abx-treated mice were highly enriched with butyrate metabolism pathway compared to water-treated mice (P < 0.05). Thus, fermented milk containing L. rhamnosus SNUG50430 was shown to ameliorate adverse health effects caused by antibiotics through modulating immune responses and the gut microbiota.

Oral Administration of Limosilactobacillus reuteri KBL346 Ameliorates Influenza Virus A/PR8 Infection in Mouse.

Influenza virus infection is an important public-health concern because of its high transmissibility and potential for severe complications. To mitigate the severity and complications of influenza, probiotics containing Lactobacillus are used and generally recognized as safe. We evaluated the anti-influenza effect of Limosilactobacillus reuteri (L. reuteri) KBL346, isolated from the fecel sample of healthy South Koreans, in mice. BALB/c mice were orally administered live and heat-inactivated L. reuteri KBL346. After infection with influenza virus (A/Puerto Rico/8/34) 0.5 times the 50% lethal dose (LD50), body weight loss was improved and recovery was accelerated. Furthermore, L. reuteri KBL346 improved body weight loss and survival rate of mice infected with 4 times the LD50 of influenza virus. Heat-inactivated L. reuteri KBL346 reduced the viral titer in the lung and the plasma immunoglobulin G level. Expression levels of genes encoding inflammatory cytokines, such as interferon-γ and toll-like receptor 2 (Tlr2), were decreased in the lung tissues of mice administered L. reuteri KBL346. Live and heat-inactivated L. reuteri KBL346 increased the expression level of Adamts4, which promotes recovery after infection, and decreased that of Tlr2. The α-diversity of the gut microbiome was modulated by the administration of L. reuteri KBL346. In addition, the structure of the gut microbial community differed according to the degree of weight loss. L. reuteri KBL346 has the potential to alleviate disease severity and improve histopathological changes in mice infected with influenza A/PR8, suggesting its efficacy as a probiotic against influenza infection.

Arcobacter in Lake Erie beach waters: an emerging gastrointestinal pathogen linked with human-associated fecal contamination.

The genus Arcobacter has been associated with human illness and fecal contamination by humans and animals. To better characterize the health risk posed by this emerging waterborne pathogen, we investigated the occurrence of Arcobacter spp. in Lake Erie beach waters. During the summer of 2010, water samples were collected 35 times from the Euclid, Villa Angela, and Headlands (East and West) beaches, located along Ohio's Lake Erie coast. After sample concentration, Arcobacter was quantified by real-time PCR targeting the Arcobacter 23S rRNA gene. Other fecal genetic markers (Bacteroides 16S rRNA gene [HuBac], Escherichia coli uidA gene, Enterococcus 23S rRNA gene, and tetracycline resistance genes) were also assessed. Arcobacter was detected frequently at all beaches, and both the occurrence and densities of Arcobacter spp. were higher at the Euclid and Villa Angela beaches (with higher levels of fecal contamination) than at the East and West Headlands beaches. The Arcobacter density in Lake Erie beach water was significantly correlated with the human-specific fecal marker HuBac according to Spearman's correlation analysis (r = 0.592; P < 0.001). Phylogenetic analysis demonstrated that most of the identified Arcobacter sequences were closely related to Arcobacter cryaerophilus, which is known to cause gastrointestinal diseases in humans. Since human-pathogenic Arcobacter spp. are linked to human-associated fecal sources, it is important to identify and manage the human-associated contamination sources for the prevention of Arcobacter-associated public health risks at Lake Erie beaches.

In vivo phycocyanin flourometry as a potential rapid screening tool for predicting elevated microcystin concentrations at eutrophic lakes.

Current approaches for assessing human health risks associated with cyanotoxins often rely on the quantification of microcystin. Significant limitations of current approaches are cost and time to obtain a result. To address these challenges, a numerical index for screening microcystin risks above the World Health Organization's (WHO) low-risk threshold for microcystin was developed for eutrophic Midwestern U.S. lakes based on water quality results from 182 beach water samples collected from seven Ohio lakes. In 48 (26.4%) samples we observed microcystin concentrations as measured by ELISA that exceeded the 4 µg/L microcystin threshold. A multivariable logistic regression model using practical real-time measures of in vivo phycocyanin (by fluorometry) and secchi depth was constructed to estimate the probability of a beach sample exceeding 4 µg/L microcystin. The final model achieved statistical significance (p = 0.030) as well as good calibration (as measured by the goodness-of-fit test comparing observed to expected counts within deciles of risk based on the model, p = 0.329) and discrimination (as indicated by the area under the receiver-operator-curve (0.795)). These results demonstrate two rapid and practical measures of recreational water quality are effective in identifying "at risk" lake conditions warranting additional management (e.g., advisory and/or advanced testing).

Co-administration of Lactobacillus gasseri KBL697 and tumor necrosis factor-alpha inhibitor infliximab improves colitis in mice.

Inflammatory bowel disease (IBD) refers to disorders involving chronic inflammation of the gastrointestinal tract. Well-established treatments for IBD have not yet to be suggested. To address this gap, we investigated the effects of co-administration of Lactobacillus gasseri (L. gasseri) KBL697 and infliximab (IFX), the first approved tumor necrosis factor (TNF)-alpha inhibitor, on the dextran sodium sulfate-induced colitis mouse model. 2 × 109 colony-forming units/g of L. gasseri KBL697 were administered to seven-week-old female C57BL/6J mice daily by oral gavage. On day three, IFX (5 mg/kg) suspended in 1 × PBS (200 µL) was intravenously injected in the IFX-treated group and all mice were sacrificed on day nine. Co-administration of L. gasseri KBL697 and IFX improved colitis symptoms in mice, including body weight, disease activity index, colon length, and histology score. Additionally, pro-inflammatory cytokines, such as interferon-gamma, interleukin (IL)-2, IL-6, IL-17A, and TNF were significantly decreased, while IL-10, an anti-inflammatory cytokine, was increased. Expression levels of tight junction genes and CD4 + CD25 + Foxp3 + T regulatory cells in the mesenteric lymph nodes were synergistically upregulated with the combined treatment. Furthermore, co-administered mice displayed altered cecum microbial diversity and composition with increases in the genus Prevotella. Related changes in the predicted amino and nucleic acid metabolic pathways were also evident, along with increased acetate and butyrate level. Therefore, the synergistic effect of L. gasseri KBL697 and IFX co-administration is a possible method of prevention and treatment for IBD.

Improved real-time quantitative reverse transcription PCR detection of norovirus following removal of inhibitors.

Human norovirus (HuNoV) is an important enteric virus that can cause large gastroenteritis outbreaks via the fecal-oral route from contaminated water and produce. Real-time quantitative reverse transcription PCR (RT-qPCR) is the only method to apply the routine detection of HuNoV in various samples, however, inhibitors present in the samples can affect the accuracy and sensitivity of RT-qPCR results. Here, we suggest an inhibitor-removal treatment for two types of noroviruses using two commercial kits. Two types of water sample (surface and seawater) and four types of produce (green onions, lettuces, radishes, and strawberries) were evaluated. The recovery efficiencies of noroviruses in water samples clearly increased in surface and seawater samples with the inhibitor-removal treatment compared to untreated samples. Moreover, murine norovirus-1 was well recovered from the four types of produce with the inhibitor-removal treatment. The mean recovery efficiencies of HuNoV genogroup II genotype 4 in lettuces and strawberries were also increased in the treated samples. Therefore, we suggest that the inhibitor-removal treatment could be useful for improving the accuracy and sensitivity of RT-qPCR methods for noroviruses in water and produce.

Isolation and characterization of a novel Escherichia coli O157:H7-specific phage as a biocontrol agent.

PURPOSE: Escherichia coli O157:H7 is one of the major foodborne pathogens of global public concern. Bacteriophages (phages) have emerged as a promising alternative to antibiotics for controlling pathogenic bacteria. Here, a lytic E. coli O157:H7-specific phage (KFS-EC) was isolated, identified, and characterized to evaluate its potential as a biocontrol agent for E. coli O157:H7. METHODS: KFS-EC was isolated from slaughterhouse in Korea. Morphological analysis, genomic analysis and several physiological tests were performed to identify and characterize the KFS-EC. RESULTS: A specificity test indicated KFS-EC was strictly specific to E. coli O157:H7 strains among 60 bacterial strains tested. Morphological and phylogenetic analyses confirmed that KFS-EC belongs to the Rb49virus genus, Tevenvirinae subfamily, and the Myoviridae family of phages. KFS-EC genome consists of 164,725 bp and a total of 270 coding sequence features, of which 114 open reading frames (ORFs) were identified as phage functional genes. KFS-EC does not contain genes encoding lysogenic property and pathogenicity, which ensure its safe application. KFS-EC was relatively stable (~1 log decrease) under stressed conditions such as temperatures (20 °C-50 °C), pHs (3-11), organic solvents (ethanol and chloroform), and biocides (0.1% citric acid, 1% citric acid, and 0.1% peracetic acid). KFS-EC was able to inhibit E. coli O157:H7 efficiently at a multiplicity of infection (MOI) of 0.01 for 8 h with greater inhibitory effect and durability and was stable at 4 °C and 22 °C over a 12-week storage period. CONCLUSIONS: Our results suggest that KFS-EC could be used as a biocontrol agent to E. coli O157:H7.

Exploring the feasibility of Salmonella Typhimurium-specific phage as a novel bio-receptor.

The purpose of this study was aimed to isolate a Salmonella Typhimurium-specific phage (KFS-ST) from washing water in a poultry processing facility and to investigate the feasibility of the KFS-ST as a novel bio-receptor for the magnetoelastic (ME) biosensor method. KFS-ST against S. Typhimurium was isolated, propagated, and purified using a CsCl-gradient ultracentrifugation. Morphological characteristics of KFS-ST were analyzed using transmission electron microscopy (TEM). Its specificity and efficiency of plating analysis were conducted against 39 foodborne pathogens. The temperature and pH stabilities of KFS-ST were investigated by the exposure of the phage to various temperatures (-70°C-70°C) and pHs (1-12) for 1 h. A one-step growth curve analysis was performed to determine the eclipse time, latent time and burst size of phage. The storage stability of KFS-ST was studied by exposing KFS-ST to various storage temperatures (-70°C, -20°C, 4°C, and 22°C) for 12 weeks. KFS-ST was isolated and purified with a high concentration of (11.47 ± 0.25) Log PFU/mL. It had an icosahedral head (56.91 ± 2.90 nm) and a non-contractile tail (225.49 ± 2.67 nm), which was classified into the family of Siphoviridae in the order of Caudovirales. KFS-ST exhibited an excellent specificity against only S. Typhimurium and S. Enteritidis, which are considered two of the most problematic Salmonella strains in the meat and poultry. However, KFS-ST did not exhibit any specificity against six other Salmonella and 27 non-Salmonella strains. KFS-ST was stable at temperature of 4°C to 50°C and at pH of 4 to 12. The eclipse time, latent time, and burst size of KFS-ST were determined to be 10 min, 25 min and 26 PFU/ infected cell, respectively. KFS-ST was relatively stable during the 12-week storage period at all tested temperatures. Therefore, this study demonstrated the feasibility of KFS-ST as a novel bio-receptor for the detection of S. Typhimurium and S. Enteritidis in meat and poultry products using the ME biosensor method.

Lactobacillus paracasei KBL382 administration attenuates atopic dermatitis by modulating immune response and gut microbiota.

Administration of probiotics has been linked to immune regulation and changes in gut microbiota composition, with effects on atopic dermatitis (AD). In this study, we investigated amelioration of the symptoms of AD using Lactobacillus paracasei KBL382 isolated from the feces of healthy Koreans. Mice with Dermatophagoides farinae extract (DFE)-induced AD were fed 1 × 109 CFU d-1 of L. paracasei KBL382 for 4 weeks. Oral administration of L. paracasei KBL382 significantly reduced AD-associated skin lesions, epidermal thickening, serum levels of immunoglobulin E, and immune cell infiltration. L. paracasei KBL382-treated mice showed decreased production of T helper (Th)1-, Th2-, and Th17-type cytokines, including thymic stromal lymphopoietin, thymus, and activation-regulated chemokine, and macrophage-derived chemokine, and increased production of the anti-inflammatory cytokine IL-10 and transforming growth factor-ß in skin tissue. Intake of L. paracasei KBL382 also increased the proportion of CD4+ CD25+ Foxp3+ regulatory T cells in mesenteric lymph nodes. In addition, administration of L. paracasei KBL382 dramatically changed the composition of gut microbiota in AD mice. Administration of KBL382 significantly ameliorates AD-like symptoms by regulating the immune response and altering the composition of gut microbiota.

Male-Specific and Somatic Coliphage Profiles from Major Aquaculture Areas in Republic of Korea.

Human and animal feces are important sources of various types of microbial contamination in water. Especially, enteric viruses, the major agents of waterborne infection, can attain long-term survival in water environments due to their strong resistance to various environmental factors including pH, salinity, and temperature. Coliphages are promising viral indicators for fecal contamination in water environments. Here, we investigated the seasonal and spatial distribution of male-specific and somatic coliphages in surface water and seawater at three major aquaculture areas, including Goseong Bay, Aphae Island, and Gomso Bay, in Republic of Korea over a period of 1 year. We selected 6 surface water and 14 seawater sampling sites for each study area and collected a total of 480 water samples from March 2014 to February 2015. Overall, surface water samples contained higher occurrences of coliphages than seawater samples. The high coliphage concentrations were detected in spring (March to May 2014). The differences in geographical features and patterns in land usage of the three aquaculture areas may have affected the coliphage concentration and occurrence. Moreover, environmental factors such as cumulative precipitation were strongly correlated with coliphage concentrations. Therefore, we suggest that further longitudinal studies on coliphage concentrations and distributions should be performed to support the application of coliphages in tracking fecal contamination in water.

Enteric viruses in raw vegetables and groundwater used for irrigation in South Korea.

Raw vegetables irrigated with groundwater that may contain enteric viruses can be associated with food-borne viral disease outbreaks. In this study, we performed reverse transcription-PCR (RT-PCR) and cell culture-PCR to monitor the occurrence of enteric viruses in groundwater samples and in raw vegetables that were cultivated using that groundwater in South Korea. Samples were collected 10 times from three farms located in Gyeonggi Province, South Korea. RT-PCR and cell culture-PCR were performed to detect adenoviruses (AdVs), enteroviruses (EVs), noroviruses (NoVs), and rotaviruses, followed by sequence analyses of the detected strains. Of the 29 groundwater samples and the 30 vegetable samples, five (17%) and three (10%) were positive for enteric viruses, respectively. AdVs were the most frequently detected viruses in four groundwater and three vegetable samples. EVs and NoVs were detected in only one groundwater sample and one spinach sample, respectively. The occurrence of enteric viruses in groundwater and vegetable samples was not correlated with the water temperature and the levels of indicator bacteria, respectively. Phylogenetic analysis indicated that most of the detected AdVs were temporally distributed, irrespective of sample type. Our results indicate that raw vegetables may be contaminated with a broad range of enteric viruses, which may originate from virus-infected farmers and virus-contaminated irrigation water, and these vegetables may act as a potential vector of food-borne viral transmission.

Concentration method for the detection of enteric viruses from large volumes of foods.

Enteric viruses are the major cause of outbreaks of foodborne viral disease worldwide, and vegetables and fruits are considered significant vectors of virus transmission. In this study, we compared viral elution concentration methods in strawberry and lettuce and tested the secondary concentration step for concentrating viruses from large volumes of lettuce samples. Among the tested procedures, the combination of a 0.05 M glycine plus 100 mM Tris elution buffer (pH 9.5) and a polyethylene glycol precipitation concentration was most efficient for the detection of norovirus genogroup II from strawberries (50% of samples) and lettuce (2.9% of samples). The secondary concentration step using ultrafiltration devices could be applied to large lettuce samples without any decrease in detection limit and efficiency, and other cultivable enteric viruses including enteroviruses, adenoviruses, and rotaviruses were recovered from lettuce at efficiencies of 11.4, 9.05, and 11.3%, respectively. This method could be useful for detecting enteric viruses in fresh foods.

Lytic KFS-SE2 phage as a novel bio-receptor for Salmonella Enteritidis detection.

Since Salmonella Enteritidis is one of the major foodborne pathogens, on-site applicable rapid detection methods have been required for its control. The purpose of this study was to isolate and purify S. Enteritidis-specific phage (KFS-SE2 phage) from an eel farm and to investigate its feasibility as a novel, efficient, and reliable bio-receptor for its employment. KFS-SE2 phage was successfully isolated at a high concentration of (2.31 ± 0.43) × 1011 PFU/ml, and consisted of an icosahedral head of 65.44 ± 10.08 nm with a non-contractile tail of 135.21 ± 12.41 nm. The morphological and phylogenetic analysis confirmed that it belongs to the Pis4avirus genus in the family of Siphoviridae. KFS-SE2 genome consisted of 48,608 bp with 45.7% of GC content. Genome analysis represented KFS-SE2 to have distinctive characteristics as a novel phage. Comparative analysis of KFS-SE2 phage with closely related strains confirmed its novelty by the presence of unique proteins. KFS-SE2 phage exhibited excellent specificity to S. Enteritidis and was stable under the temperature range of 4 to 50°C and pH of 3 to 11 (P < 0.05). The latent time was determined to be 20 min. Overall, a new lytic KFS-SE2 phage was successfully isolated from the environment at a high concentration and the excellent feasibility of KFS-SE2 phage was demonstrated as a new bio-receptor for S. Enteritidis detection.

The genetic diversity of human noroviruses detected in river water in Korea.

We studied the genetic diversity of human noroviruses in river waters by RT-nested PCR and phylogenetic analysis. During 2002-2003, water samples were collected from four rivers in Gyeonggi Province, South Korea. Among the 58 samples, 32 (55.2%) and 26 (44.8%) showed positive results with noroviruses belonging to genogroups I (GI) and II (GII), respectively. The phylogenetic analysis grouped 8 and 7 genotypes in GI and GII, respectively. The major types were GI/1, GI/13, and GII/15, and GI/1 and GI/3 were temporarily distributed. Most GI- and GII-grouped strains were closely related to the reference strains from neighboring countries, China and Japan, and GII/4-related strains had similar sequences to strains recognized as worldwide epidemic outbreaks. The strains circulating between countries are of particular concern to the outbreaks of noroviral diseases in Korea and must be periodically monitored in the natural environments.

Molecular detection of human enteric viruses in urban rivers in Korea.

We performed RT-nested PCR to study the distribution of human enteric viruses in urban rivers in Korea. During 2002-2003, water samples were collected from four rivers in Gyeonggi Province, South Korea. Among 58 samples, 45 (77.6%), 32 (55.2%), 12 (20.7%), 2 (3.4%), 4 (6.9%), and 4 (6.9%) showed positive results with adenoviruses (AdVs), enteroviruses (EVs), reoviruses (ReVs), hepatitis A viruses (HAVs), rotaviruses (RoVs), and sapoviruses (SVs), respectively. According to the binary logistic regression model, the occurrence of each enteric virus, except ReVs and HAVs, was not statistically correlated with the water temperature and levels of fecal coliforms (P<0.05). AdVs were most often detected; only 4 samples (6.9%) were negative for AdVs while positive for other enteric viruses in the studied sites. Our results indicated that monitoring human enteric viruses is necessary to improve microbial quality, and that AdVs detection by PCR can be a useful index for the presence of other enteric viruses in aquatic environments.

Comparison of Swab Sampling Methods for Norovirus Recovery on Surfaces.

Human noroviruses (HuNoVs) can be easily transferred by the contacts of humans or fomites. Swab sampling methods are widely used for recovering HuNoVs from small surfaces of various fomites or hard-to-reach locations and swab sampling conditions are important for the accurate detection of HuNoVs, which have a low infectious dose and relatively long persistence under a range of environmental conditions. Therefore, to determine the suitable swab sampling method for recovering HuNoVs from various surfaces, we evaluated combinations of four swab materials (cotton, microdenier polyester [a type of microfiber], polyurethane foam, and rayon) and three elution buffer solutions (phosphate-buffered saline [PBS], PBS with 0.2% Tween-80, and 3% beef extract-50 mM glycine [pH 9.5]). First, we inoculated HuNoVs or murine noroviruses (MuNoVs), the surrogate of HuNoVs, onto test coupons (10 × 10 cm) consisting of three common surface materials (high-density polyethylene, stainless steel, and wood). Coupons were swabbed using a combination of each swab material and elution buffer, and the viral recovery was measured by real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) or plaque assay. By RT-qPCR, we confirmed that the cotton swab-PBS and microdenier polyester-PBS combinations had recovery efficiencies greater than 80% for viruses on plastic and stainless steel surfaces. The cotton swab-PBS combination had the highest recovery efficiency on all surface materials via the plaque assay. Therefore, a cotton or a microdenier polyester swab with PBS could be a useful method for sampling HuNoVs on various surfaces.

Disinfection of waterborne viruses using silver nanoparticle-decorated silica hybrid composites in water environments.

Silver nanoparticles (AgNPs) have been reported as an effective alternative for controlling a broad-spectrum of pathogenic viruses. We developed a micrometer-sized silica hybrid composite decorated with AgNPs (AgNP-SiO2) to prevent the inherent aggregation of AgNPs, and facilitated their recovery from environmental media after use. The production process had a high-yield, and fabrication was cost-effective. We evaluated the antiviral capabilities of Ag30-SiO2 particles against two model viruses, bacteriophage MS2 and murine norovirus (MNV), in four different types of water (deionized, tap, surface, and ground). MNV was more susceptible to Ag30-SiO2 particles in all four types of water compared to MS2. Furthermore, several water-related factors, including temperature and organic matter content, were shown to affect the antimicrobial capabilities of Ag30-SiO2 particles. The modified Hom model was the best-fit disinfection model for MNV disinfection in the different types of water. Additionally, this study demonstrated that the effects of a certain level of physical obstacles in water were negligible in regards to the use of Ag30-SiO2 particles. Thus, effective use of AgNPs in water disinfection processes can be achieved using our novel hybrid composites to inactivate various waterborne viruses.

Inactivation of influenza A virus via exposure to silver nanoparticle-decorated silica hybrid composites.

Influenza A virus (IFV-A) is one of the main cause of seasonal flu and can infect various of host species via the reassortment of segmented RNA genomes. Silver nanoparticles (AgNPs) have been known as excellent antiviral agent against IFV. However, the use of free AgNPs has several major drawbacks, including the inherent aggregation among AgNPs and unwanted cytotoxic or genotoxic damages for human body via inhalation or ingestion. In this study, we assessed the efficacy of our novel ~ 30-nm-diameter AgNP-decorated silica hybrid composite (Ag30-SiO2; ~ 400 nm in diameter) for IFV-A inactivation. Ag30-SiO2 particles can inhibit IFV-A effectively in a clear dose-dependent manner. However, when real-time RT-PCR assay was used, merely 0.5-log10 reduction of IFV-A was observed at both 5 and 20 °C. Moreover, even after 1 h of exposure to Ag30-SiO2 particles, more than 80% of hemagglutinin (HA) damage and 20% of neuraminidase (NA) activities had occurred, and the infection of Madin-Darby Canine Kidney (MDCK) cells by IFV-A was reduced. The results suggested that the major antiviral mechanism of Ag30-SiO2 particles is the interaction with viral components located at the membrane. Therefore, Ag30-SiO2 particles can cause nonspecific damage to various IFV-A components and be used as an effective method for inactivating IFV-A.

Host-Specific Bacteroides Markers-Based Microbial Source Tracking in Aquaculture Areas.

Various waterborne pathogens originate from human or animal feces and may cause severe gastroenteric outbreaks. Bacteroides spp. that exhibit strong host- or group-specificities are promising markers for identifying fecal sources and their origins. In the present study, 240 water samples were collected from two major aquaculture areas in Republic of Korea over a period of approximately 1 year, and the concentrations and occurrences of four host-specific Bacteroides markers (human, poultry, pig, and ruminant) were evaluated in the study areas. Host-specific Bacteroides markers were detected widely in the study areas, among which the poultry-specific Bacteroides marker was detected at the highest concentration (1.0-1.2 log10 copies L-1). During the sampling period, high concentrations of host-specific Bacteroides markers were detected between September and December 2015. The host-specific Bacteroides marker-combined geospatial map revealed the up-to-downstream gradient of fecal contamination, as well as the effects of land-use patterns on host-specific Bacteroides marker concentrations. In contrast to traditional bacterial indicators, the human-specific Bacteroides marker correlated with human specific pathogens, such as noroviruses (r=0.337; P<0.001). The present results indicate that host-specific Bacteroides genetic markers with an advanced geospatial analysis are useful for tracking fecal sources and associated pathogens in aquaculture areas.