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  1. Article ; Online: Toward Standardized Aerovirology: A Critical Review of Existing Results and Methodologies.

    Groth, Robert / Niazi, Sadegh / Oswin, Henry P / Haddrell, Allen E / Spann, Kirsten / Morawska, Lidia / Ristovski, Zoran

    Environmental science & technology

    2024  Volume 58, Issue 8, Page(s) 3595–3608

    Abstract: Understanding the airborne survival of viruses is important for public health and epidemiological modeling and potentially to develop mitigation strategies to minimize the transmission of airborne pathogens. Laboratory experiments typically involve ... ...

    Abstract Understanding the airborne survival of viruses is important for public health and epidemiological modeling and potentially to develop mitigation strategies to minimize the transmission of airborne pathogens. Laboratory experiments typically involve investigating the effects of environmental parameters on the viability or infectivity of a target airborne virus. However, conflicting results among studies are common. Herein, the results of 34 aerovirology studies were compared to identify links between environmental and compositional effects on the viability of airborne viruses. While the specific experimental apparatus was not a factor in variability between reported results, it was determined that the experimental procedure was a major factor that contributed to discrepancies in results. The most significant contributor to variability between studies was poorly defined initial viable virus concentration in the aerosol phase, causing many studies to not measure the rapid inactivation, which occurs quickly after particle generation, leading to conflicting results. Consistently, studies that measured their reference airborne viability minutes after aerosolization reported higher viability at subsequent times, which indicates that there is an initial loss of viability which is not captured in these studies. The composition of the particles which carry the viruses was also found to be important in the viability of airborne viruses; however, the mechanisms for this effect are unknown. Temperature was found to be important for aerosol-phase viability, but there is a lack of experiments that directly compare the effects of temperature in the aerosol phase and the bulk phase. There is a need for repeated measurements between different research groups under identical conditions both to assess the degree of variability between studies and also to attempt to better understand already published data. Lack of experimental standardization has hindered the ability to quantify the differences between studies, for which we provide recommendations for future studies. These recommendations are as follows: measuring the reference airborne viability using the "direct method"; use equipment which maximizes time resolution; quantify all losses appropriately; perform, at least, a 5- and 10-min sample, if possible; report clearly the composition of the virus suspension; measure the composition of the gas throughout the experiment. Implementing these recommendations will address the most significant oversights in the existing literature and produce data which can more easily be quantitatively compared.
    MeSH term(s) Viruses ; Aerosols
    Chemical Substances Aerosols
    Language English
    Publishing date 2024-02-14
    Publishing country United States
    Document type Journal Article ; Review
    ISSN 1520-5851
    ISSN (online) 1520-5851
    DOI 10.1021/acs.est.3c07275
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: An assessment of the airborne longevity of group A Streptococcus.

    Oswin, Henry P / Blake, Evie / Haddrell, Allen E / Finn, Adam / Sriskandan, Shiranee / Reid, Jonathan P / Halliday, Alice / Goenka, Anu

    Microbiology (Reading, England)

    2024  Volume 170, Issue 1

    Abstract: Group A streptococcus (GAS) infections result in more than 500 000 deaths annually. Despite mounting evidence for airborne transmission of GAS, little is known about its stability in aerosol. Measurements of GAS airborne stability were carried out using ... ...

    Abstract Group A streptococcus (GAS) infections result in more than 500 000 deaths annually. Despite mounting evidence for airborne transmission of GAS, little is known about its stability in aerosol. Measurements of GAS airborne stability were carried out using the Controlled Electrodynamic Levitation and Extraction of Bioaerosols onto a Substrate (CELEBS) instrument. CELEBS measurements with two different isolates of GAS suggest that it is aerostable, with approximately 70 % of bacteria remaining viable after 20 min of levitation at 50 % relative humidity (RH), with lower survival as RH was reduced. GAS airborne viability loss was driven primarily by desiccation and efflorescence (i.e. salt crystallization), with high pH also potentially playing a role, given reduced survival in bicarbonate containing droplet compositions. At low enough RH for efflorescence to occur, a greater proportion of organic components in the droplet appeared to protect the bacteria from efflorescence. These first insights into the aerosol stability of GAS indicate that airborne transmission of these respiratory tract bacteria may occur, and that both the composition of the droplet containing the bacteria, and the RH of the air affect the duration of bacterial survival in this environment. Future studies will explore a broader range of droplet and air compositions and include a larger selection of GAS strains.
    MeSH term(s) Streptococcus pyogenes ; Sodium Chloride ; Aerosols
    Chemical Substances Sodium Chloride (451W47IQ8X) ; Aerosols
    Language English
    Publishing date 2024-01-05
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1180712-x
    ISSN 1465-2080 ; 1350-0872
    ISSN (online) 1465-2080
    ISSN 1350-0872
    DOI 10.1099/mic.0.001421
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: How to engineer aerosol particle properties and biopharmaceutical performance of propellant inhalers.

    Akhuemokhan, Precious / Green, Natalie Armstrong / Haddrell, Allen / Lewis, David / Reid, Jonathan P / Forbes, Ben

    International journal of pharmaceutics

    2023  Volume 634, Page(s) 122676

    Abstract: Given the environmental compulsion to reformulate pressurised metered dose inhalers (pMDI) using new propellants with lower global warming potential, this study investigated how non-volatile excipients can be used to engineer aerosol particle ... ...

    Abstract Given the environmental compulsion to reformulate pressurised metered dose inhalers (pMDI) using new propellants with lower global warming potential, this study investigated how non-volatile excipients can be used to engineer aerosol particle microphysics and drug release. The dynamics of change in particle size, wetting and physical state were measured for single particles (glycerol/ethanol/beclomethasone dipropionate; BDP) in the aerosol phase at different relative humidity (RH) using an electrodynamic balance. BDP dissolution rates were compared for aerosols from pMDI containing different ratios of BDP:glycerol or BDP:isopropyl myristate (IPM). In 45 % RH, ethanol loss was followed by evaporation of condensed water to generate spherical particles with solid inclusions or compact irregular-shaped solid particles, according to the presence or absence of glycerol. In RH > 95 %, condensed water did not evaporate and BDP formed solid inclusions in water/glycerol or water droplets. Varying the non-volatile component, 0-50 % w/w, in pMDI resulted in a concentration-dependent 4-8-fold reduction in BDP dissolution rate. These findings demonstrate that non-volatile excipients provide a means of engineering aerosol properties and, modifying the rate of drug release from aerosol medicines. We also demonstrated differences between particles formed in vitro in ambient humidity versus higher humidity, more like that encountered during oral inhalation.
    MeSH term(s) Glycerol ; Biological Products ; Excipients ; Aerosols ; Nebulizers and Vaporizers ; Metered Dose Inhalers ; Beclomethasone ; Administration, Inhalation ; Ethanol ; Water ; Aerosol Propellants ; Particle Size ; Hydrocarbons, Fluorinated
    Chemical Substances Glycerol (PDC6A3C0OX) ; Biological Products ; Excipients ; Aerosols ; Beclomethasone (KGZ1SLC28Z) ; Ethanol (3K9958V90M) ; Water (059QF0KO0R) ; Aerosol Propellants ; Hydrocarbons, Fluorinated
    Language English
    Publishing date 2023-02-03
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 428962-6
    ISSN 1873-3476 ; 0378-5173
    ISSN (online) 1873-3476
    ISSN 0378-5173
    DOI 10.1016/j.ijpharm.2023.122676
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Oxidative Stress Contributes to Bacterial Airborne Loss of Viability.

    Oswin, Henry P / Haddrell, Allen E / Hughes, Cordelia / Otero-Fernandez, Mara / Thomas, Richard J / Reid, Jonathan P

    Microbiology spectrum

    2023  , Page(s) e0334722

    Abstract: While the airborne decay of bacterial viability has been observed for decades, an understanding of the mechanisms driving the decay has remained elusive. The airborne transport of bacteria is often a key step in their life cycle and as such, ... ...

    Abstract While the airborne decay of bacterial viability has been observed for decades, an understanding of the mechanisms driving the decay has remained elusive. The airborne transport of bacteria is often a key step in their life cycle and as such, characterizing the mechanisms driving the airborne decay of bacteria is an essential step toward a more complete understanding of microbial ecology. Using the Controlled Electrodynamic Levitation and Extraction of Bioaerosols onto a Substrate (CELEBS), it was possible to systematically evaluate the impact of different physicochemical and environmental parameters on the survival of Escherichia coli in airborne droplets of Luria Bertani broth. Rather than osmotic stress driving the viability loss, as was initially considered, oxidative stress was found to play a key role. As the droplets evaporate and equilibrate with the surrounding environment, the surface-to-volume ratio increases, which in turn increased the formation of reactive oxygen species in the droplet. These reactive oxygen species appear to play a key role in driving the airborne loss of viability of E. coli.
    Language English
    Publishing date 2023-03-13
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2807133-5
    ISSN 2165-0497 ; 2165-0497
    ISSN (online) 2165-0497
    ISSN 2165-0497
    DOI 10.1128/spectrum.03347-22
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Aerobiology: Experimental Considerations, Observations, and Future Tools.

    Haddrell, Allen E / Thomas, Richard J

    Applied and environmental microbiology

    2017  Volume 83, Issue 17

    Abstract: Understanding airborne survival and decay of microorganisms is important for a range of public health and biodefense applications, including epidemiological and risk analysis modeling. Techniques for experimental aerosol generation, retention in the ... ...

    Abstract Understanding airborne survival and decay of microorganisms is important for a range of public health and biodefense applications, including epidemiological and risk analysis modeling. Techniques for experimental aerosol generation, retention in the aerosol phase, and sampling require careful consideration and understanding so that they are representative of the conditions the bioaerosol would experience in the environment. This review explores the current understanding of atmospheric transport in relation to advances and limitations of aerosol generation, maintenance in the aerosol phase, and sampling techniques. Potential tools for the future are examined at the interface between atmospheric chemistry, aerosol physics, and molecular microbiology where the heterogeneity and variability of aerosols can be explored at the single-droplet and single-microorganism levels within a bioaerosol. The review highlights the importance of method comparison and validation in bioaerosol research and the benefits that the application of novel techniques could bring to increasing the understanding of aerobiological phenomena in diverse research fields, particularly during the progression of atmospheric transport, where complex interdependent physicochemical and biological processes occur within bioaerosol particles.
    MeSH term(s) Aerosols/analysis ; Air Microbiology ; Bacteria/classification ; Bacteria/genetics ; Bacteria/isolation & purification ; Microbiological Techniques/instrumentation ; Microbiological Techniques/methods ; Microbiological Techniques/trends ; Particle Size
    Chemical Substances Aerosols
    Language English
    Publishing date 2017-08-17
    Publishing country United States
    Document type Journal Article ; Review ; Research Support, Non-U.S. Gov't
    ZDB-ID 223011-2
    ISSN 1098-5336 ; 0099-2240
    ISSN (online) 1098-5336
    ISSN 0099-2240
    DOI 10.1128/AEM.00809-17
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Ambient carbon dioxide concentration correlates with SARS-CoV-2 aerostability and infection risk.

    Haddrell, Allen / Oswin, Henry / Otero-Fernandez, Mara / Robinson, Joshua F / Cogan, Tristan / Alexander, Robert / Mann, Jamie F S / Hill, Darryl / Finn, Adam / Davidson, Andrew D / Reid, Jonathan P

    Nature communications

    2024  Volume 15, Issue 1, Page(s) 3487

    Abstract: An improved understanding of the underlying physicochemical properties of respiratory aerosol that influence viral infectivity may open new avenues to mitigate the transmission of respiratory diseases such as COVID-19. Previous studies have shown that an ...

    Abstract An improved understanding of the underlying physicochemical properties of respiratory aerosol that influence viral infectivity may open new avenues to mitigate the transmission of respiratory diseases such as COVID-19. Previous studies have shown that an increase in the pH of respiratory aerosols following generation due to changes in the gas-particle partitioning of pH buffering bicarbonate ions and carbon dioxide is a significant factor in reducing SARS-CoV-2 infectivity. We show here that a significant increase in SARS-CoV-2 aerostability results from a moderate increase in the atmospheric carbon dioxide concentration (e.g. 800 ppm), an effect that is more marked than that observed for changes in relative humidity. We model the likelihood of COVID-19 transmission on the ambient concentration of CO
    MeSH term(s) Carbon Dioxide/metabolism ; Carbon Dioxide/analysis ; COVID-19/transmission ; COVID-19/virology ; Humans ; SARS-CoV-2 ; Hydrogen-Ion Concentration ; Aerosols ; Humidity ; Ventilation ; Respiratory Aerosols and Droplets/metabolism ; Respiratory Aerosols and Droplets/virology ; Atmosphere/chemistry
    Chemical Substances Carbon Dioxide (142M471B3J) ; Aerosols
    Language English
    Publishing date 2024-04-25
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-024-47777-5
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article: Water Uptake by Evaporating pMDI Aerosol Prior to Inhalation Affects Both Regional and Total Deposition in the Respiratory System.

    Legh-Land, Victoria / Haddrell, Allen E / Lewis, David / Murnane, Darragh / Reid, Jonathan P

    Pharmaceutics

    2021  Volume 13, Issue 7

    Abstract: As pulmonary drug deposition is a function of aerosol particle size distribution, it is critical that the dynamics of particle formation and maturation in pMDI sprays in the interim between generation and inhalation are fully understood. This paper ... ...

    Abstract As pulmonary drug deposition is a function of aerosol particle size distribution, it is critical that the dynamics of particle formation and maturation in pMDI sprays in the interim between generation and inhalation are fully understood. This paper presents an approach to measure the evaporative and condensational fluxes of volatile components and water from and to solution pMDI droplets following generation using a novel technique referred to as the Single Particle Electrodynamic Lung (SPEL). In doing so, evaporating aerosol droplets are shown capable of acting as condensation nuclei for water. Indeed, we show that the rapid vaporisation of volatile components from a volatile droplet is directly correlated to the volume of water taken up by condensation. Furthermore, a significant volume of water is shown to condense on droplets of a model pMDI formulation (hydrofluoroalkane (HFA), ethanol and glycerol) during evaporative droplet ageing, displaying a dramatic shift from a core composition of a volatile species to that of predominantly water (non-volatile glycerol remained in this case). This yields a droplet with a water activity of 0.98 at the instance of inhalation. The implications of these results on regional and total pulmonary drug deposition are explored using the International Commission of Radiological Protection (ICRP) deposition model, with an integrated semi-analytical treatment of hygroscopic growth. Through this, droplets with water activity of 0.98 upon inhalation are shown to produce markedly different dose deposition profiles to those with lower water activities at the point of inspiration.
    Language English
    Publishing date 2021-06-24
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2527217-2
    ISSN 1999-4923
    ISSN 1999-4923
    DOI 10.3390/pharmaceutics13070941
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Transformative Approach To Investigate the Microphysical Factors Influencing Airborne Transmission of Pathogens.

    Otero Fernandez, Mara / Thomas, Richard J / Oswin, Henry / Haddrell, Allen E / Reid, Jonathan P

    Applied and environmental microbiology

    2020  Volume 86, Issue 23

    Abstract: Emerging outbreaks of airborne pathogenic infections worldwide, such as the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, have raised the need to understand parameters affecting the airborne survival of microbes in order ... ...

    Abstract Emerging outbreaks of airborne pathogenic infections worldwide, such as the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, have raised the need to understand parameters affecting the airborne survival of microbes in order to develop measures for effective infection control. We report a novel experimental strategy, TAMBAS (tandem approach for microphysical and biological assessment of airborne microorganism survival), to explore the synergistic interactions between the physicochemical and biological processes that impact airborne microbe survival in aerosol droplets. This innovative approach provides a unique and detailed understanding of the processes taking place from aerosol droplet generation through to equilibration and viability decay in the local environment, elucidating decay mechanisms not previously described. The impact of evaporation kinetics, solute hygroscopicity and concentration, particle morphology, and equilibrium particle size on airborne survival are reported, using
    MeSH term(s) Aerosols ; Air Microbiology ; Betacoronavirus/physiology ; COVID-19 ; Coronavirus Infections/transmission ; Cough/microbiology ; Crystallization ; Escherichia coli/physiology ; Escherichia coli Infections/transmission ; Humans ; Infection Control/methods ; Microbial Viability ; Pandemics ; Particle Size ; Pneumonia, Viral/transmission ; SARS-CoV-2 ; Sneezing/physiology
    Chemical Substances Aerosols
    Keywords covid19
    Language English
    Publishing date 2020-11-10
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 223011-2
    ISSN 1098-5336 ; 0099-2240
    ISSN (online) 1098-5336
    ISSN 0099-2240
    DOI 10.1128/AEM.01543-20
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Differences in airborne stability of SARS-CoV-2 variants of concern is impacted by alkalinity of surrogates of respiratory aerosol.

    Haddrell, Allen / Otero-Fernandez, Mara / Oswin, Henry / Cogan, Tristan / Bazire, James / Tian, Jianghan / Alexander, Robert / Mann, Jamie F S / Hill, Darryl / Finn, Adam / Davidson, Andrew D / Reid, Jonathan P

    Journal of the Royal Society, Interface

    2023  Volume 20, Issue 203, Page(s) 20230062

    Abstract: The mechanistic factors hypothesized to be key drivers for the loss of infectivity of viruses in the aerosol phase often remain speculative. Using a next-generation bioaerosol technology, we report measurements of the aero-stability of several SARS-CoV-2 ...

    Abstract The mechanistic factors hypothesized to be key drivers for the loss of infectivity of viruses in the aerosol phase often remain speculative. Using a next-generation bioaerosol technology, we report measurements of the aero-stability of several SARS-CoV-2 variants of concern in aerosol droplets of well-defined size and composition at high (90%) and low (40%) relative humidity (RH) upwards of 40 min. When compared with the ancestral virus, the infectivity of the Delta variant displayed different decay profiles. At low RH, a loss of viral infectivity of approximately 55% was observed over the initial 5 s for both variants. Regardless of RH and variant, greater than 95% of the viral infectivity was lost after 40 min of being aerosolized. Aero-stability of the variants correlate with their sensitivities to alkaline pH. Removal of all acidic vapours dramatically increased the rate of infectivity decay, with 90% loss after 2 min, while the addition of nitric acid vapour improved aero-stability. Similar aero-stability in droplets of artificial saliva and growth medium was observed. A model to predict loss of viral infectivity is proposed: at high RH, the high pH of exhaled aerosol drives viral infectivity loss; at low RH, high salt content limits the loss of viral infectivity.
    MeSH term(s) Humans ; SARS-CoV-2/genetics ; COVID-19/epidemiology ; Respiratory Aerosols and Droplets
    Language English
    Publishing date 2023-06-21
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2156283-0
    ISSN 1742-5662 ; 1742-5689
    ISSN (online) 1742-5662
    ISSN 1742-5689
    DOI 10.1098/rsif.2023.0062
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Assessing the airborne survival of bacteria in populations of aerosol droplets with a novel technology.

    Fernandez, Mara Otero / Thomas, Richard J / Garton, Natalie J / Hudson, Andrew / Haddrell, Allen / Reid, Jonathan P

    Journal of the Royal Society, Interface

    2019  Volume 16, Issue 150, Page(s) 20180779

    Abstract: The airborne transmission of infection relies on the ability of pathogens to survive aerosol transport as they transit between hosts. Understanding the parameters that determine the survival of airborne microorganisms is critical to mitigating the impact ...

    Abstract The airborne transmission of infection relies on the ability of pathogens to survive aerosol transport as they transit between hosts. Understanding the parameters that determine the survival of airborne microorganisms is critical to mitigating the impact of disease outbreaks. Conventional techniques for investigating bioaerosol longevity in vitro have systemic limitations that prevent the accurate representation of conditions that these particles would experience in the natural environment. Here, we report a new approach that enables the robust study of bioaerosol survival as a function of relevant environmental conditions. The methodology uses droplet-on-demand technology for the generation of bioaerosol droplets (1 to greater than 100 per trial) with tailored chemical and biological composition. These arrays of droplets are captured in an electrodynamic trap and levitated within a controlled environmental chamber. Droplets are then deposited on a substrate after a desired levitation period (less than 5 s to greater than 24 h). The response of bacteria to aerosolization can subsequently be determined by counting colony forming units, 24 h after deposition. In a first study, droplets formed from a suspension of Escherichia coli MRE162 cells (10
    MeSH term(s) Aerosols ; Escherichia coli/metabolism ; Microbial Viability ; Models, Biological
    Chemical Substances Aerosols
    Language English
    Publishing date 2019-04-08
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2156283-0
    ISSN 1742-5662 ; 1742-5689
    ISSN (online) 1742-5662
    ISSN 1742-5689
    DOI 10.1098/rsif.2018.0779
    Database MEDical Literature Analysis and Retrieval System OnLINE

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