Benthic sediment as stores and sources of bacteria and viruses in streams:A comparison of baseflow vs. stormflow longitudinal transport and residence times

International audienceThe presence of bacteria and viruses in freshwater represents a global health risk. The substantial spatial and temporal variability of microbes leads to difficulties in quantifying the risks associated with their presence in freshwater. Fine particles, including bacteria and viruses are transported and accumulated into shallow streambed (i.e., benthic) sediment, delaying the downstream transmission during baseflow conditions but contributing to their resuspension and transport downstream during stormflow events. Direct measurements of pathogen accumulation in benthic sediments are rare. Until now, the dynamic role of benthic sediment as both a store and source of microbes, has not been quantified. In this study, we analyze microbial abundance in benthic sediment along a 1 km reach of an intermittent Mediterranean stream receiving inputs from the effluent of a wastewater treatment plant, a known point source of microbes in streams. We sampled benthic sediment during a summer drought when the wastewater effluent constituted 100% of the stream flow, and thus, large accumulation and persistence of pathogens along the streambed was expected. We measured the abundance of total bacteria, Escherichia coli (as a fecal indicator), and presence of enteric rotavirus (RoV) and norovirus (NoV). The abundance of E. coli, based on qPCR detection, was high (4.99∙102 g/cm2 or ∼ 1 ng/μL) along the first 100 m downstream of the wastewater effluent input and in general decreased with distance from the source, with presence of RoV and NoV along the study reach. A particle tracking model was applied, that uses stream water velocity as an input, and accounts for microbial exchange into, immobilization, degradation, and resuspension out of benthic sediment during baseflow and stormflow. Rates of exchange into benthic sediment were 3 orders of magnitude higher during stormflow, but residence times were proportionately lower, resulting in increased longitudinal connectivity from up to downstream during stormflow. Model simulations demonstrated mechanistically how the rates of exchange into and out of the benthic sediment resulted in benthic sediment to act as a store during baseflow and a source during stormflow

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic

Fast purification of the filamentous Potato virus Y using monolithic chromatographic supports

International audienceObtaining pure virus suspensions is an essential step in many applications, such as vaccine production, antibody production, sample preparation for procedures requiring enrichment in viruses and other in vitro characterizations. Purification procedures usually consist of complex, long lasting and tedious protocols involving several ultracentrifugation steps. Such complexity is particularly evident in the case of plant viruses, where the virus needs to be isolated from the complex plant tissue matrix. Convective Interaction Media (CIM) monoliths are chromatographic supports that have been successfully utilized for the purification of large bio-molecules such as viruses, virus like particles and plasmids from various matrixes. In this study a CIM monolith based procedure was developed for the fast purification from plant tissue of the filamentous Potato virus Y(PVY) (virion size, 740 nm x 11 nm), which is one of the most important plant viruses causing great economical losses in potato production. Different mobile phases, chemistries and sample preparation strategies were tested. The presence of the virus in the chromatographic fraction was monitored with viral RNA quantification (RT-qPCR), viral protein purity estimation (SDS-PAGE) and viral particle integrity observation (transmission electron microscopy). The optimized procedure involves initial clarification steps, followed by chromatography using CIM quaternary amine (QA) monolithic disk column. In comparison to classical purification procedure involving ultracentrifugation through sucrose and caesium chloride, the developed CIM-QA purification achieved comparable yield, concentration and purity. Plant nucleic acids were successfully removed. Purification showed good reproducibility and moreover it reduced the purification time from four working days required for classic purification to a day and a half. This is the first study where a filamentous virus was purified using CIM monolithic supports. The advantages of this new purification procedure make it an attractive method in serological diagnostic tool production, which requires purified viruses for the immunization step. Moreover, the outcome of this study could serve as starting point for the improvement of the purification methods of other important filamentous viruses. (C) 2012 Elsevier B.V. All rights reserved

Inactivation of the enveloped virus phi6 with hydrodynamic cavitation

The COVID −19 pandemic reminded us that we need better contingency plans to prevent the spread of infectious agents and the occurrence of epidemics or pandemics. Although the transmissibility of SARS-CoV-2 in water has not been confirmed, there are studies that have reported on the presence of infectious coronaviruses in water and wastewater samples. Since standard water treatments are not designed to eliminate viruses, it is of utmost importance to explore advanced treatment processes that can improve water treatment and help inactivate viruses when needed. This is the first study to investigate the effects of hydrodynamic cavitation on the inactivation of bacteriophage phi6, an enveloped virus used as a SARS-CoV-2 surrogate in many studies. In two series of experiments with increasing and constant sample temperature, virus reduction of up to 6.3 logs was achieved. Inactivation of phi6 at temperatures of 10 and 20 °C occurs predominantly by the mechanical effect of cavitation and results in a reduction of up to 4.5 logs. At 30 °C, the reduction increases to up to 6 logs, where the temperature-induced increased susceptibility of the viral lipid envelope makes the virus more prone to inactivation. Furthermore, the control experiments without cavitation showed that the increased temperature alone is not sufficient to cause inactivation, but that additional mechanical stress is still required. The RNA degradation results confirmed that virus inactivation was due to the disrupted lipid bilayer and not to RNA damage. Hydrodynamic cavitation, therefore, has the potential to inactivate current and potentially emerging enveloped pathogenic viruses in water at lower, environmentally relevant temperatures