Persistence of E. coli O157:H7 in urban recreational waters from Spring and Autumn: a comparison analysis.

People might get infected by pathogens found in urban recreational waters during water-contact activities, such as swimming, boating, bathing, and yachting. However, the persistence of pathogenic bacteria in those waters was not well documented. In this study, persistence of E. coli O157:H7 (EcO157) in 48 water samples (24 Spring samples and 24 Autumn samples) from the 3 urban recreational waters was investigated. Multivariate statistical analysis was performed to correlate survival data with water physicochemical properties and bacterial communities. Our data showed that EcO157 survived longer in Spring samples than in Autumn samples regardless of the lakes. Results revealed that recreational water physicochemical properties and bacterial community in Spring samples were different from those in Autumn samples. Mantel and Partial Mantel tests, as well as co-occurrence network analysis illustrated that EC salinity, TOC, and bacterial community were correlated with survival time (ttd) (p < 0.05). Variation partition analysis (VPA) indicated that bacterial community, EC, TOC, and TN explained about 64.81% of overall ttd variation in Spring samples, and bacterial community, EC, pH, and TP accounted for about 56.59% of overall ttd variation in Autumn samples. Structural equation model (SEM) illustrated that EC indirectly positively affected ttd through bacterial community. The correlation between bacterial community and ttd was negative in Spring samples and positive in Autumn samples. TN appeared a direct positive effect on ttd in Spring samples. TP displayed a direct negative effect on ttd in Autumn samples. Our results concluded that there was seasonal variation in environmental factors that directly or indirectly affected the survival of EcO157 in urban recreational waters.

Persistence of Salmonella Typhimurium in apple-pear (Pyrus bretschneideri Rehd.) orchard soils influenced by bacterial communities and soil properties.

2In this study, we investigated the persistence of Salmonella Typhimurium in 26 soil samples from apple-pear orchards in Yanji, Longjing and Helong in northeastern China. The time to reach detection limit (ttds) of Salmonella Typhimurium in soils varied from 20 to 120 days. Redundancy analysis and variation partition analysis elucidated that bacterial communities, clay content, pH, electrical conductivity (EC) salinity, and NO3--N could explain more than 85% of overall variation of the persistence behaviors. Results of structural equation models and Mantel tests revealed that clay content and EC displayed both direct and indirect effect on ttds, while NO3--N and pH exhibited direct and indirect effect on the survival patterns, respectively. Furthermore, Actinobacteria, Acidobacteria and Deltaproteobacteria at class level showed highly close correlations with ttds. Our results revealed that certain biotic and abiotic factors could greatly contribute to the overall persistence of Salmonella in apple-pear orchard soils.

Disentangling survival of Escherichia coli O157:H7 in soils: From a subpopulation perspective.

Soil physicochemical properties and microbial community have been proved to be correlated to survival behaviors of Shiga toxin-producing Escherichia coli O157:H7, but the roles of biotic and abiotic factors in the different stages of inactivation process remain unclear. Here, fruit producing soils were collected, and soils physicochemical properties, bacterial and fungal community structure were characterized. Survival experiments were performed by inoculating E. coli O157:H7 in soils. Double Weibull survival model was found to better fit the experimental data, and two subpopulations with different capability on resistance to stress were identified. The sensitive subpopulation with smaller δ (time needed for first decimal reduction) (i.e., δ1) died off faster compared to the more resistant subpopulation with greater δ (i.e., δ2). Partial Mantel test revealed that ttd (time needed to reach detection limit) was jointly influenced by physical factors, chemical factors, and bacterial composition (P < 0.05); δ1 was shaped by physical factors (P < 0.01) and additional bacterial composition (P < 0.05); and δ2 was strongly steered by bacterial community (P < 0.001). Bacterial co-occurrence network analysis revealed that samples with lower δ2 were coupled with higher network complexity and closer taxa relationship (e.g. higher average (weighted) degree, higher network diameter, higher graph density, and lower modularity), and vice versa. Taken together, the sensitive subpopulation had difficulty in adapting to coarse particles conditions, while resistant subpopulation might eventually succumb to the robust biodiversity. This study provides novel insights into the E. coli O157:H7 survival mechanism through subpopulation perspective and sheds light on the reduction of edaphic colonization by pathogens via agricultural management strategy.

Interaction between Fungal Communities, Soil Properties, and the Survival of Invading E. coli O157:H7 in Soils.

Pathogens that invade into the soil cancontaminate food and water, andinfect animals and human beings. It is well documented that individual bacterial phyla are well correlated with the survival of E. coliO157 (EcO157), while the interaction betweenthe fungal communities and EcO157 survival remains largely unknown. In this study, soil samples from Tongliao, Siping, and Yanji in northeast China were collected and characterized. Total DNA was extracted for fungal and bacterial community characterization. EcO157 cells were spiked into the soils, and their survival behavior was investigated. Results showed that both fungal and bacterial communities were significantly correlated (p < 0.01) with the survival of EcO157 in soils, and the relative abundances of fungal groups (Dothideomycetes and Sordariomycetes) and some bacterial phyla (Acidobacteria, Firmicutes, gamma- and delta-Proteobacteria)weresignificantly correlated with ttds (p < 0.01). Soil pH, EC (electric conductance) salinity, and water-soluble nitrate nitrogen were significantly correlated with survival time (time to reach the detection limit, ttd) (p < 0.05). The structural equation model indicated that fungal communities could directly influence ttds, and soil properties could indirectly influence the ttds through fungal communities. The first log reduction time (δ) was mainly correlated with soil properties, while the shape parameter (p) was largely correlated with fungal communities. Our data indicated that both fungal and bacterial communities were closely correlated (p < 0.05)with the survival of EcO157 in soils, and different fungal and bacterial groups might play different roles. Fungal communities and bacterial communities explained 5.87% and 17.32% of the overall variation of survival parameters, respectively. Soil properties explained about one-third of the overall variation of survival parameters. These findings expand our current understanding of the environmental behavior of human pathogens in soils.

Occurrence, distribution, and ecological risk of pharmaceuticals in a seasonally ice-sealed river: From ice formation to melting.

Occurrence, distribution, and ecological risk of 21 pharmaceuticals in the Jilin Songhua River were investigated during its freeze-thaw periods, including ice formation, sealed, and breakup. Florfenicol was the most abundant pharmaceutical, with mean concentrations of 123.4 ± 61.1 ng L-1 in water and 73.8 ± 66.3 ng kg-1 in ice. Sulfadiazine occurred at a higher mean concentration in downstream areas (45.6 ± 7.4 ng L-1) than in upstream areas (0.7 ± 0.7 ng L-1). Most pharmaceuticals appeared in relatively high concentrations in water during the ice-breakup period. Complex factors including pharmaceutical usage patterns, ice-regulated photodegradation, biodegradation, water flow, and freeze-concentration effects, as well as the release of pharmaceuticals from ice, were responsible for the temporal variation of pharmaceuticals. Pseudo-ice/water distribution coefficients showed the distribution of pharmaceuticals in ice and demonstrated the effects of their release from the ice on their temporal variations. Most pharmaceuticals posed a risk to algae; of these, amoxicillin exhibited the highest risk. In addition, thawing increased the concentration of thiamphenicol in water, which elevated its ecological risk level. The findings suggest that the pharmaceuticals retained in ice should be considered with regard to regulating pharmaceuticals' temporal variations in seasonal ice-covered rivers during the freeze-thaw process.