Antibiotic resistance genes and the association with bacterial community in biofilms occurring during the drinking water granular activated carbon (GAC) sandwich biofiltration

The granular activated carbon (GAC) sandwich modification to slow sand filtration could be considered as a promising technology for improved drinking water quality. Biofilms developed on sand and GAC surfaces are expected to show a functional diversity during the biofiltration. Bench-scale GAC sandwich biofilters were set-up and run continuously with and without antibiotic exposure. Surface sand (the schmutzdecke) and GAC biofilms were sampled and subject to high-throughput qPCR for antibiotic resistance gene (ARG) analysis and 16 S rRNA amplicon sequencing. Similar diversity of ARG profile was found in both types of biofilms, suggesting that all ARG categories decreased in richness along the filter bed. In general, surface sand biofilm remained the most active layer with regards to the richness and abundance of ARGs, where GAC biofilms showed slightly lower ARG risks. Network analysis suggested that 10 taxonomic genera were implicated as possible ARG hosts, among which Nitrospira, Methyloversatilis and Methylotenera showed the highest correlation. Overall, this study was the first attempt to consider the whole structure of the GAC sandwich biofilter and results from this study could help to further understand the persistence of ARGs and their association with the microbial community in drinking water biofiltration system

Enhanced detoxification of Cr6+ by Shewanella oneidensis via adsorption on spherical and flower-like manganese ferrite nanostructures

Maximizing the safe removal of hexavalent chromium (Cr6+) from waste streams is an increasing demand due to the environmental, economic and health benefits. The integrated adsorption and bio-reduction method can be applied for the elimination of the highly toxic Cr6+ and its detoxification. This work describes a synthetic method for achieving the best chemical composition of spherical and flower-like manganese ferrite (MnxFe3-xO4) nanostructures (NS) for Cr6+ adsorption. We selected NS with the highest adsorption performance to study its efficiency in the extracellular reduction of Cr6+ into a trivalent state (Cr3+) by Shewanella oneidensis (S. oneidensis) MR-1. MnxFe3-xO4 NS were prepared by a polyol solvothermal synthesis process. They were characterised by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), dynamic light scattering (DLS) and Fourier transform-infrared (FTIR) spectroscopy. The elemental composition of MnxFe3-xO4 was evaluated by inductively coupled plasma atomic emission spectroscopy. Our results reveal that the oxidation state of the manganese precursor significantly affects the Cr6+ adsorption efficiency of MnxFe3-xO4 NS. The best adsorption capacity for Cr6+ is 16.8 ± 1.6 mg Cr6+/g by the spherical Mn0.22+Fe2.83+O4 nanoparticles at pH 7, which is 1.4 times higher than that of Mn0.8Fe2.2O4 nanoflowers. This was attributed to the relative excess of divalent manganese in Mn0.22+Fe2.83+O4 based on our XPS analysis. The lethal concentration of Cr6+ for S. oneidensis MR-1 was 60 mg L-1 (determined by flow cytometry). The addition of Mn0.22+Fe2.83+O4 nanoparticles to S. oneidensis MR-1 enhanced the bio-reduction of Cr6+ 2.66 times compared to the presence of the bacteria alone. This work provides a cost-effective method for the removal of Cr6+ with a minimum amount of sludge production

Findings and Guidance for Airborne Infection Resilience

This guidance provides insights into airborne infection risks and proposes mitigation measures to improve airborne infection resilience of indoor and semi-outdoor spaces. In some poorly-ventilated and/or highly occupied spaces, the provision of increased ventilation performance can be the key to reducing airborne infection risk down to 'acceptable' (although currently undefined) levels.This is a complex area of study with many areas of uncertainty that form the basis of ongoing research. That said, the AIRBODS programme, in the context of the global research efforts associated with the COVID-19 pandemic, has generated a sound basis for improving airborne infection resilience. Key aspects of the guide with its many recommendations include:• Experiments carried out in a test chamber showing how screens can improve or, even, worsen airborne infection risk.• Field studies undertaken as part of the Events Research Programme which underpinned the opening up of the UK hospitality sector in summer of 2021. Good practice advice is provided on how to drive high resolution CO2 and microbiological studies and then appropriately interpret results.• Analytical models were developed to understand how infection risk, using a mass balance approach with many different parameters, might be mitigated in some circumstances when compared to reference spaces. These models were then developed into a 'full building' tool which can be downloaded as part of this guidance.• Computational fluid dynamics (CFD) models were developed to provide insights into the physics of droplets or aerosols at microscale. Following completion of a test chamber validation exercise, models were developed to investigate breathing or coughing mannequins at single human moving towards audience or crowd scale.Local ventilation effectiveness and associated airborne infection risk aspects of some real spaces may significantly differ from assumed 'fully-mixed' equivalent spaces. This, along with a number of other issues, will form part of ongoing research activities.• Focus groups were also used to provide some wider context and support some of our recommendations.AIRBODS has produced a repository of data and modelling methods with the mindset of enabling building professionals to inform their design and operation decisions towards improving airborne infection resilience in their buildings

Household slow sand filters in intermittent and continuous flows to treat water containing low mineral ion concentrations and Bisphenol A

Household slow sand filter (HSSF) has been used as an alternative to drinking water treatment in rural communities worldwide; however, its performance to treat influent water with quality similar to rainwater still needs further studies. Rainwater presents low pH and slight mineral ion concentrations, an aspect that can modify the filter media and consequently the HSSF efficiency. Furthermore, house roofs used in rainwater harvesting can be made of plastic. Therefore, it can introduce chemicals such as Bisphenol A (BPA) in the water. In this context, two pilot-scale HSSFs operated in continuous and intermittent flows were evaluated to treat water containing BPA and low mineral ion concentrations in order to assess the filter performance. Filter media leaching was noticed in the trials; thus, filter media and construction material selection must be carefully evaluated to eliminate risks of pollutant occurrence in drinking water. Operational differences between continuous and intermittent flows influenced the HSSF efficiency for BPA and DOC removals; even so, the filters' performance was low probably due to the slow schmutzdecke development. According to tracer test results, HSSF can be classified as a plug flow reactor and strategies to improve its hydraulic performance are not required

AIRBODS: Findings and guidance for airborne infection resilience

This guidance provides insights into airborne infection risks and proposes mitigation measures to improve airborne infection resilience of indoor and semi-outdoor spaces. In some poorly-ventilated and/or highly occupied spaces, the provision of increased ventilation performance can be the key to reducing airborne infection risk down to 'acceptable' (although currently undefined) levels.This is a complex area of study with many areas of uncertainty that form the basis of ongoing research. That said, the AIRBODS programme, in the context of the global research efforts associated with the COVID-19 pandemic, has generated a sound basis for improving airborne infection resilience. Key aspects of the guide with its many recommendations include:•Experiments carried out in a test chamber showing how screens can improve or, even, worsen airborne infection risk.•Field studies undertaken as part of the Events Research Programme which underpinned the opening up of the UK hospitality sector in summer of 2021. Good practice advice is provided on how to drive high resolution CO2 and microbiological studies and then appropriately interpret results.• Analytical models were developed to understand how infection risk, using a mass balance approach with many different parameters, might be mitigated in some circumstances when compared to reference spaces. These models were then developed into a 'full building' tool which can be downloaded as part of this guidance.• Computational fluid dynamics (CFD) models were developed to provide insights into the physics of droplets or aerosols at microscale.Following completion of a test chamber validation exercise, models were developed to investigate breathing or coughing mannequins at single human moving towards audience or crowd scale. Local ventilation effectiveness and associated airborne infection risk aspects of some real spaces may significantly differ from assumed 'fully-mixed' equivalent spaces. This, along with a number of other issues, will form part of ongoing research activities.• Focus groups were also used to provide some wider context and support some of our recommendations.AIRBODS has produced a repository of data and modelling methods with the mindset of enabling building professionals to inform their design and operation decisions towards improving airborne infection resilience in their buildings

A large strain elasto-viscoplastic numerical model

peer reviewedA large strain elasto-viscoplastic Perzyna model was proposed by Ponthot. The resultant numerical model computes the elastic response using an hypoelastic model. A viscoplastic multiplier was proposed, then both inviscid (elastoplastic) and elastic limiting cases can be easily recovered. More recently the authors have included this viscoplastic model in a large strain constitutive model based on hyperelasticity and multiplicative decomposition of deformation gradient tensor. In this work a brief summary of both, hypoelastic and hyperelastic based large strain models of viscoplasticity is provided. Large strain examples are simulated in order to test the discussed models. Different parameters of the constitutive model are tested in order to study the sensitivity of the resultant algorithm. From the obtained results can be said that both models show a very good agree and represent very well the characteristic of the viscoplastic constitutive model

Molecular Basis of Resistance to Macrolides and Other Antibiotics in Commensal Viridans Group Streptococci and Gemella spp. and Transfer of Resistance Genes to Streptococcus pneumoniae

We assessed the mechanisms of resistance to macrolide-lincosamide-streptogramin B (MLS(B)) antibiotics and related antibiotics in erythromycin-resistant viridans group streptococci (n = 164) and Gemella spp. (n = 28). The macrolide resistance phenotype was predominant (59.38%); all isolates with this phenotype carried the mef(A) or mef(E) gene, with mef(E) being predominant (95.36%). The erm(B) gene was always detected in strains with constitutive and inducible MLS(B) resistance and was combined with the mef(A/E) gene in 47.44% of isolates. None of the isolates carried the erm(A) subclass erm(TR), erm(A), or erm(C) genes. The mel gene was detected in all but four strains carrying the mef(A/E) gene. The tet(M) gene was found in 86.90% of tetracycline-resistant isolates and was strongly associated with the presence of the erm(B) gene. The cat(pC194) gene was detected in seven chloramphenicol-resistant Streptococcus mitis isolates, and the aph(3′)-III gene was detected in four viridans group streptococcal isolates with high-level kanamycin resistance. The intTn gene was found in all isolates with the erm(B), tet(M), aph(3′)-III, and cat(pC194) gene. The mef(E) and mel genes were successfully transferred from both groups of bacteria to Streptococcus pneumoniae R6 by transformation. Viridans group streptococci and Gemella spp. seem to be important reservoirs of resistance genes

Findings and Guidance for Airborne Infection Resilience

This guidance provides insights into airborne infection risks and proposes mitigation measures to improve airborne infection resilience of indoor and semi-outdoor spaces. In some poorly-ventilated and/or highly occupied spaces, the provision of increased ventilation performance can be the key to reducing airborne infection risk down to 'acceptable' (although currently undefined) levels.This is a complex area of study with many areas of uncertainty that form the basis of ongoing research. That said, the AIRBODS programme, in the context of the global research efforts associated with the COVID-19 pandemic, has generated a sound basis for improving airborne infection resilience. Key aspects of the guide with its many recommendations include:• Experiments carried out in a test chamber showing how screens can improve or, even, worsen airborne infection risk.• Field studies undertaken as part of the Events Research Programme which underpinned the opening up of the UK hospitality sector in summer of 2021. Good practice advice is provided on how to drive high resolution CO2 and microbiological studies and then appropriately interpret results.• Analytical models were developed to understand how infection risk, using a mass balance approach with many different parameters, might be mitigated in some circumstances when compared to reference spaces. These models were then developed into a 'full building' tool which can be downloaded as part of this guidance.• Computational fluid dynamics (CFD) models were developed to provide insights into the physics of droplets or aerosols at microscale. Following completion of a test chamber validation exercise, models were developed to investigate breathing or coughing mannequins at single human moving towards audience or crowd scale.Local ventilation effectiveness and associated airborne infection risk aspects of some real spaces may significantly differ from assumed 'fully-mixed' equivalent spaces. This, along with a number of other issues, will form part of ongoing research activities.• Focus groups were also used to provide some wider context and support some of our recommendations.AIRBODS has produced a repository of data and modelling methods with the mindset of enabling building professionals to inform their design and operation decisions towards improving airborne infection resilience in their buildings