Airborne Microorganisms

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Kevin G Kerr - One of the best experts on this subject based on the ideXlab platform.

  • methodology for determining the susceptibility of Airborne Microorganisms to irradiation by an upper room uvgi system
    Journal of Aerosol Science, 2006
    Co-Authors: Clive B Beggs, L. A. Fletcher, Catherine J Noakes, P Andrew Sleigh, Kevin G Kerr
    Abstract:

    Abstract Whilst a number of researchers have demonstrated the disinfection effectiveness of upper-room UV irradiation devices against a range of Airborne Microorganisms, it is technically difficult to determine the performance of such systems because the biological and physical processes involved can be complex. In particular, most of the quantitative data on the susceptibility of Airborne Microorganisms to UV irradiation is obtained from single-pass experiments which are not representative of the fragmented UV exposure experienced by Airborne Microorganisms in real rooms. This paper presents complete and partial mixing models for predicting an effective UV susceptibility constant, Z eff , that is appropriate for quantifying the behaviour of Airborne Microorganisms when irradiated using an upper-room system. The use of both decay and continuous contamination experimental techniques are discussed and related to the models presented. Experimental results are presented which indicate that Z eff for Serratia marcescens is up to an order of magnitude lower than the susceptibility constants derived from single-pass experiments, suggesting that using these data to design upper-room UV systems may lead to a lower than expected performance.

  • development of a numerical model to simulate the biological inactivation of Airborne Microorganisms in the presence of ultraviolet light
    Journal of Aerosol Science, 2004
    Co-Authors: Catherine J Noakes, L. A. Fletcher, P Andrew Sleigh, Clive B Beggs, Kevin G Kerr
    Abstract:

    The effectiveness of any ultraviolet germicidal irradiation (UVGI) system is governed by the passage of Airborne Microorganisms through the UV field. This paper describes a new method for evaluating the performance of UVGI devices using computational fluid dynamic (CFD) simulations. A microorganism inactivation equation is combined with a scalar transport equation to describe the concentration of Airborne Microorganisms in the presence of a UV field. The solution of this equation, in conjunction with the momentum and turbulent energy equations, allows the effect of both the airflow and the UV field on the microorganism distribution to be examined. Solutions are shown for the airflow and microorganism concentration through a bench scale flow apparatus, at five different UV intensities. The results from the CFD model are validated against the experimental data, obtained from the flow apparatus, for aerosolised Pseudomonas aeruginosa Microorganisms. Good comparisons are seen, giving confidence in the application of the technique to other situations.

Sergey A. Grinshpun - One of the best experts on this subject based on the ideXlab platform.

  • sampling for Airborne Microorganisms
    2007
    Co-Authors: Sergey A. Grinshpun, Mark P Buttner, Gediminas Mainelis, Klaus Willeke
    Abstract:

    Microbiologists have confronted the challenges of sampling and analysis of Airborne Microorganisms since the early 20th century. Today, the concentration and composition of Airborne Microorganisms are of interest in various areas such as agricultural and industrial settings, hospitals, home and office environments, and military installations. In all of these applications, the term "bioaerosol" is used to refer to Airborne biological particles, such as bacterial cells, fungal spores, viruses, and pollen grains, and to their fragments and by-products. A wide variety of bioaerosol sampling and analysis methods have been used, and new methods are being developed. However, no single sampling method is suitable for the collection and analysis of all types of bioaerosols and no standardized protocols are currently available. Therefore, data from different studies are often difficult to compare because of differences in sampler designs, collection times, airflow rates, collection media and analysis methods. In addition, human exposure limits have not been established for bioaerosols because of the lack of exposure, dose, and response data. The purpose of this chapter is to present various bioaerosol sampling and analysis methods that would allow facilitating an intelligent selection of instrumentation and techniques. The principles of bioaerosol sampling are presented, followed by a review of traditional and emerging sampling methods and techniques, including the results of performance evaluations of the various sampler types. Equipment calibration and air sampling considerations such as collection times and the number of samples are discussed. The advantages and disadvantages of surface sampling methods are also described.

  • assessment of electrical charge on Airborne Microorganisms by a new bioaerosol sampling method
    Journal of Occupational and Environmental Hygiene, 2004
    Co-Authors: Klaus Willeke, Tiina Reponen, Gediminas Mainelis, Atin Adhikari, Hongxia Wang, Sergey A. Grinshpun
    Abstract:

    Bioaerosol sampling is necessary to monitor and control human exposure to harmful Airborne Microorganisms. An important parameter affecting the collection of Airborne Microorganisms is the electrical charge on the Microorganisms. Using a new design of an electrostatic precipitator (ESP) for bioaerosol sampling, the polarity and relative strength of the electrical charges on Airborne Microorganisms were determined in several laboratory and field environments by measuring the overall physical collection efficiency and the biological collection efficiency at specific precipitation voltages and polarities. First, bacteria, fungal spores, and dust dispersed from soiled carpets were sampled in a walk-in test chamber. Second, a simulant of anthrax-causing Bacillus anthracis spores was dispersed and sampled in the same chamber. Third, bacteria were sampled in a small office while four adults were engaged in lively discussions. Fourth, bacteria and fungal spores released from hay and horse manure were sampled in a...

  • collection of Airborne Microorganisms by a new electrostatic precipitator
    Journal of Aerosol Science, 2002
    Co-Authors: Gediminas Mainelis, Tiina Reponen, Klaus Willeke, Atin Adhikari, Sergey A. Grinshpun
    Abstract:

    Bioaerosol exposure assessment and the protection of civil/governmental/military establishments from bioterrorism require the development of low-power bioaerosol collectors that are able not only to efficiently collect Airborne Microorganisms, but also to preserve their biological integrity. In search for such a method, a new bioaerosol sampler was evaluated. In this device, the Airborne Microorganisms are imparted electrical charges and are then deposited in an electrical field onto a growth medium (agar). Experiments were conducted with Pseudomonas fluorescens vegetative cells, Bacillus subtilis var. niger (BG) endospores (used to simulate the spores of anthrax-causing Bacillus anthracis when testing bioaerosol sensors) and Penicillium brevicompactum fungal spores. It was found that 80–90% of initially “charge-neutralized” biological particles were removed from the air, when a small amount of ionization was generated in the electrostatic precipitator's (ESP) inlet and a precipitation voltage of ±4000V was applied across the agar plates. Over 70% of viable BG and P. brevicompactum spores entering the ESP were enumerated as colony forming units. The bioefficiency of the new sampler was about the same as that of the Biosampler, which was tested in parallel. In experiments with sensitive P. fluorescens vegetative cells, the ESP enumerated twice as many cells as the Biosampler. The latter result indicates that the electrostatic collection method may be especially useful for the collection and enumeration of sensitive Airborne Microorganisms. Experiments investigating the effect of aging time on the amount of electrical charge carried by the Airborne Microorganisms showed that the level of electrical charge gradually decreases with increasing aging time. However, even after the P. fluorescens cells had remained Airborne for an hour, they retained enough electrical charge to be collected with efficiency higher than 70%.

  • induction charging and electrostatic classification of micrometer size particles for investigating the electrobiological properties of Airborne Microorganisms
    Aerosol Science and Technology, 2002
    Co-Authors: Gediminas Mainelis, Sergey A. Grinshpun, Klaus Willeke, Paul A Baron, Tiina Reponen
    Abstract:

    Our earlier studies have shown that the electrostatic collection technique, a potentially "gentle" bioaerosol collection method, allows for efficient collection of Airborne bacteria, but sensitive bacteria such as Pseudomonas fluorescens ( P. fluorescens ) lose their culturability during collection. We hypothesized that excessive stress was imposed on the sensitive bacteria by the sampler's conventional corona charging mechanism. In this research, we developed and built an experimental setup that allows us to analyze electrobiological properties of Airborne Microorganisms. In this experimental system, we imparted electric charges on Airborne biological and nonbiological particles by aerosolizing them in the presence of an electric field. The charged P. fluorescens test bacteria and NaCl test particles were then channeled into a parallel plate mobility analyzer, which we have designed so that bacteria and inert particles carrying specific charge ranges can be extracted and made available for further analys...

  • development and evaluation of a new personal sampler for culturable Airborne Microorganisms
    Atmospheric Environment, 2002
    Co-Authors: Igor E Agranovski, Victoria Agranovski, Klaus Willeke, Tiina Reponen, Sergey A. Grinshpun
    Abstract:

    The objective of this study was to develop a new personal sampler for viable Airborne Microorganisms and to evaluate its performance under controlled laboratory conditions and in a field. In the sampler, air is bubbled through a porous medium submerged in a liquid layer, as has earlier been demonstrated to be highly efficient for air purification. The prototype had the physical collection efficiency >95% for particles >0.32 μm in aerodynamic diameter during 8 h of continuous operation. The pressure drop across the sampler was below 1700 Pa, much lower than that of most conventional bioaerosol samplers. The collection liquid losses due to evaporation and aerosolization did not exceed 18% in 8 h and the culturability of sampled Microorganisms remained high: the recovery rate of stress-sensitive gram-negative P. fluorescens bacteria was 61±20%; for stress-resistant B. subtilis bacteria and A. versicolor fungal spores it was 95±9% and 97±6%, respectively. Six identical personal samplers were tested simultaneously on a simplified human manikin in an office environment. The culturable microbial concentration data obtained during 2, 4 and 8-h sampling were not affected by the sampling time. Inter-sample variation did not exceed 30%. The laboratory and field evaluations have demonstrated that the new sampler is capable of long-term personal sampling of Airborne culturable Microorganisms. The estimation of the detection limits has indicated that the sampler is capable of monitoring microbial exposure in the environments with the bacterial concentrations above 15 CFU/m3 and fungal concentrations above 5 CFU/m3 when using a sampling time of 8 h.

Catherine J Noakes - One of the best experts on this subject based on the ideXlab platform.

  • methodology for determining the susceptibility of Airborne Microorganisms to irradiation by an upper room uvgi system
    Journal of Aerosol Science, 2006
    Co-Authors: Clive B Beggs, L. A. Fletcher, Catherine J Noakes, P Andrew Sleigh, Kevin G Kerr
    Abstract:

    Abstract Whilst a number of researchers have demonstrated the disinfection effectiveness of upper-room UV irradiation devices against a range of Airborne Microorganisms, it is technically difficult to determine the performance of such systems because the biological and physical processes involved can be complex. In particular, most of the quantitative data on the susceptibility of Airborne Microorganisms to UV irradiation is obtained from single-pass experiments which are not representative of the fragmented UV exposure experienced by Airborne Microorganisms in real rooms. This paper presents complete and partial mixing models for predicting an effective UV susceptibility constant, Z eff , that is appropriate for quantifying the behaviour of Airborne Microorganisms when irradiated using an upper-room system. The use of both decay and continuous contamination experimental techniques are discussed and related to the models presented. Experimental results are presented which indicate that Z eff for Serratia marcescens is up to an order of magnitude lower than the susceptibility constants derived from single-pass experiments, suggesting that using these data to design upper-room UV systems may lead to a lower than expected performance.

  • development of a numerical model to simulate the biological inactivation of Airborne Microorganisms in the presence of ultraviolet light
    Journal of Aerosol Science, 2004
    Co-Authors: Catherine J Noakes, L. A. Fletcher, P Andrew Sleigh, Clive B Beggs, Kevin G Kerr
    Abstract:

    The effectiveness of any ultraviolet germicidal irradiation (UVGI) system is governed by the passage of Airborne Microorganisms through the UV field. This paper describes a new method for evaluating the performance of UVGI devices using computational fluid dynamic (CFD) simulations. A microorganism inactivation equation is combined with a scalar transport equation to describe the concentration of Airborne Microorganisms in the presence of a UV field. The solution of this equation, in conjunction with the momentum and turbulent energy equations, allows the effect of both the airflow and the UV field on the microorganism distribution to be examined. Solutions are shown for the airflow and microorganism concentration through a bench scale flow apparatus, at five different UV intensities. The results from the CFD model are validated against the experimental data, obtained from the flow apparatus, for aerosolised Pseudomonas aeruginosa Microorganisms. Good comparisons are seen, giving confidence in the application of the technique to other situations.

  • Development of a numerical model to simulate the biological inactivation of Airborne Microorganisms in the presence of ultraviolet light
    Journal of Aerosol Science, 2004
    Co-Authors: Catherine J Noakes, L. A. Fletcher, P Andrew Sleigh, Clive B Beggs, K. G. Kerr
    Abstract:

    The effectiveness of any ultraviolet germicidal irradiation (UVGI) system is governed by the passage of Airborne Microorganisms through the UV field. This paper describes a new method for evaluating the performance of UVGI devices using computational fluid dynamic (CFD) simulations. A microorganism inactivation equation is combined with a scalar transport equation to describe the concentration of Airborne Microorganisms in the presence of a UV field. The solution of this equation, in conjunction with the momentum and turbulent energy equations, allows the effect of both the airflow and the UV field on the microorganism distribution to be examined. Solutions are shown for the airflow and microorganism concentration through a bench scale flow apparatus, at five different UV intensities. The results from the CFD model are validated against the experimental data, obtained from the flow apparatus, for aerosolised Pseudomonas aeruginosa Microorganisms. Good comparisons are seen, giving confidence in the application of the technique to other situations. © 2003 Elsevier Ltd. All rights reserved.

Clive B Beggs - One of the best experts on this subject based on the ideXlab platform.

  • methodology for determining the susceptibility of Airborne Microorganisms to irradiation by an upper room uvgi system
    Journal of Aerosol Science, 2006
    Co-Authors: Clive B Beggs, L. A. Fletcher, Catherine J Noakes, P Andrew Sleigh, Kevin G Kerr
    Abstract:

    Abstract Whilst a number of researchers have demonstrated the disinfection effectiveness of upper-room UV irradiation devices against a range of Airborne Microorganisms, it is technically difficult to determine the performance of such systems because the biological and physical processes involved can be complex. In particular, most of the quantitative data on the susceptibility of Airborne Microorganisms to UV irradiation is obtained from single-pass experiments which are not representative of the fragmented UV exposure experienced by Airborne Microorganisms in real rooms. This paper presents complete and partial mixing models for predicting an effective UV susceptibility constant, Z eff , that is appropriate for quantifying the behaviour of Airborne Microorganisms when irradiated using an upper-room system. The use of both decay and continuous contamination experimental techniques are discussed and related to the models presented. Experimental results are presented which indicate that Z eff for Serratia marcescens is up to an order of magnitude lower than the susceptibility constants derived from single-pass experiments, suggesting that using these data to design upper-room UV systems may lead to a lower than expected performance.

  • development of a numerical model to simulate the biological inactivation of Airborne Microorganisms in the presence of ultraviolet light
    Journal of Aerosol Science, 2004
    Co-Authors: Catherine J Noakes, L. A. Fletcher, P Andrew Sleigh, Clive B Beggs, Kevin G Kerr
    Abstract:

    The effectiveness of any ultraviolet germicidal irradiation (UVGI) system is governed by the passage of Airborne Microorganisms through the UV field. This paper describes a new method for evaluating the performance of UVGI devices using computational fluid dynamic (CFD) simulations. A microorganism inactivation equation is combined with a scalar transport equation to describe the concentration of Airborne Microorganisms in the presence of a UV field. The solution of this equation, in conjunction with the momentum and turbulent energy equations, allows the effect of both the airflow and the UV field on the microorganism distribution to be examined. Solutions are shown for the airflow and microorganism concentration through a bench scale flow apparatus, at five different UV intensities. The results from the CFD model are validated against the experimental data, obtained from the flow apparatus, for aerosolised Pseudomonas aeruginosa Microorganisms. Good comparisons are seen, giving confidence in the application of the technique to other situations.

  • Development of a numerical model to simulate the biological inactivation of Airborne Microorganisms in the presence of ultraviolet light
    Journal of Aerosol Science, 2004
    Co-Authors: Catherine J Noakes, L. A. Fletcher, P Andrew Sleigh, Clive B Beggs, K. G. Kerr
    Abstract:

    The effectiveness of any ultraviolet germicidal irradiation (UVGI) system is governed by the passage of Airborne Microorganisms through the UV field. This paper describes a new method for evaluating the performance of UVGI devices using computational fluid dynamic (CFD) simulations. A microorganism inactivation equation is combined with a scalar transport equation to describe the concentration of Airborne Microorganisms in the presence of a UV field. The solution of this equation, in conjunction with the momentum and turbulent energy equations, allows the effect of both the airflow and the UV field on the microorganism distribution to be examined. Solutions are shown for the airflow and microorganism concentration through a bench scale flow apparatus, at five different UV intensities. The results from the CFD model are validated against the experimental data, obtained from the flow apparatus, for aerosolised Pseudomonas aeruginosa Microorganisms. Good comparisons are seen, giving confidence in the application of the technique to other situations. © 2003 Elsevier Ltd. All rights reserved.

Gediminas Mainelis - One of the best experts on this subject based on the ideXlab platform.

  • performance of personal electrostatic bioaerosol sampler pebs when collecting Airborne Microorganisms
    Journal of Aerosol Science, 2018
    Co-Authors: Nirmala Thomas, Gediminas Mainelis
    Abstract:

    Abstract We recently developed a new personal electrostatic bioaerosol sampler (PEBS) for determining exposures to Airborne Microorganisms. PEBS was shown to collect Airborne non-biological particles with efficiencies approaching 80% while producing very low ozone concentrations. In this work, we analyzed the performance of this sampler when collecting Airborne Bacillus atrophaeus bacterial cells and Penicillium chrysogenum fungal spores as a function of sampling flow rates (e.g., 10 and 20 L/min) and sampling time (e.g., 10, 60, and 240 min). The collected samples were analyzed using microscopy, adenosine triphosphate (ATP)-based bioluminescence, flow cytometry (Live/Dead test), and culture techniques. PEBS's physical and biological performance was compared against that of BioSampler (SKC Inc., Eighty Four, PA) when the samplers were operated at 10 and 12.5 L/min, respectively. PEBS achieved physical collection efficiency as high as 83%, and its physical performance in terms of measured bioaerosol concentration was better than that of BioSampler. In addition, a fraction of live Microorganisms recovered by PEBS was not different from that of BioSampler. Compared to BioSampler, PEBS measured similar or higher concentrations of culturable bacteria, but lower concentrations of culturable spores. The Airborne ATP concentration measured by PEBS was significantly higher than that measured by BioSampler. Overall, we show that PEBS is a viable and efficient technology to determine personal exposures to Airborne Microorganisms using multiple sample analysis techniques.

  • sampling for Airborne Microorganisms
    2007
    Co-Authors: Sergey A. Grinshpun, Mark P Buttner, Gediminas Mainelis, Klaus Willeke
    Abstract:

    Microbiologists have confronted the challenges of sampling and analysis of Airborne Microorganisms since the early 20th century. Today, the concentration and composition of Airborne Microorganisms are of interest in various areas such as agricultural and industrial settings, hospitals, home and office environments, and military installations. In all of these applications, the term "bioaerosol" is used to refer to Airborne biological particles, such as bacterial cells, fungal spores, viruses, and pollen grains, and to their fragments and by-products. A wide variety of bioaerosol sampling and analysis methods have been used, and new methods are being developed. However, no single sampling method is suitable for the collection and analysis of all types of bioaerosols and no standardized protocols are currently available. Therefore, data from different studies are often difficult to compare because of differences in sampler designs, collection times, airflow rates, collection media and analysis methods. In addition, human exposure limits have not been established for bioaerosols because of the lack of exposure, dose, and response data. The purpose of this chapter is to present various bioaerosol sampling and analysis methods that would allow facilitating an intelligent selection of instrumentation and techniques. The principles of bioaerosol sampling are presented, followed by a review of traditional and emerging sampling methods and techniques, including the results of performance evaluations of the various sampler types. Equipment calibration and air sampling considerations such as collection times and the number of samples are discussed. The advantages and disadvantages of surface sampling methods are also described.

  • utilization of natural electrical charges on Airborne Microorganisms for their collection by electrostatic means
    Journal of Aerosol Science, 2006
    Co-Authors: Gediminas Mainelis
    Abstract:

    Abstract Bioaerosol exposure assessment requires effective Airborne microorganism collection methods. This research investigates whether the natural electrical charges on Airborne Microorganisms can be utilized for their collection by electrostatic means. To test this hypothesis, a new sampling device (Electrosampler), which deposits Airborne Microorganisms onto agar collection medium by electrostatic means, was designed and built. Different from traditional electrostatic precipitators, this device features no charging of incoming particles. The performance of the new sampler when collecting culturable bacteria and fungi in indoor and outdoor environments was compared against a traditional microbial impactor operated in parallel. The testing was performed for three different collection flow rates (1.2, 5, and 10 L/min) at a fixed electrostatic field strength of 5 kV/cm inside the collection chamber. For all testing conditions, the Electrosampler recovered more Airborne Microorganisms than the impactor with a difference as large as 5–9 times under certain conditions. The obtained data indicate that utilization of natural microorganism charge and electrostatic collection technique may provide a bioaerosol sampling method with higher recovery of culturable Airborne Microorganisms compared to inertia-based techniques.

  • assessment of electrical charge on Airborne Microorganisms by a new bioaerosol sampling method
    Journal of Occupational and Environmental Hygiene, 2004
    Co-Authors: Klaus Willeke, Tiina Reponen, Gediminas Mainelis, Atin Adhikari, Hongxia Wang, Sergey A. Grinshpun
    Abstract:

    Bioaerosol sampling is necessary to monitor and control human exposure to harmful Airborne Microorganisms. An important parameter affecting the collection of Airborne Microorganisms is the electrical charge on the Microorganisms. Using a new design of an electrostatic precipitator (ESP) for bioaerosol sampling, the polarity and relative strength of the electrical charges on Airborne Microorganisms were determined in several laboratory and field environments by measuring the overall physical collection efficiency and the biological collection efficiency at specific precipitation voltages and polarities. First, bacteria, fungal spores, and dust dispersed from soiled carpets were sampled in a walk-in test chamber. Second, a simulant of anthrax-causing Bacillus anthracis spores was dispersed and sampled in the same chamber. Third, bacteria were sampled in a small office while four adults were engaged in lively discussions. Fourth, bacteria and fungal spores released from hay and horse manure were sampled in a...

  • collection of Airborne Microorganisms by a new electrostatic precipitator
    Journal of Aerosol Science, 2002
    Co-Authors: Gediminas Mainelis, Tiina Reponen, Klaus Willeke, Atin Adhikari, Sergey A. Grinshpun
    Abstract:

    Bioaerosol exposure assessment and the protection of civil/governmental/military establishments from bioterrorism require the development of low-power bioaerosol collectors that are able not only to efficiently collect Airborne Microorganisms, but also to preserve their biological integrity. In search for such a method, a new bioaerosol sampler was evaluated. In this device, the Airborne Microorganisms are imparted electrical charges and are then deposited in an electrical field onto a growth medium (agar). Experiments were conducted with Pseudomonas fluorescens vegetative cells, Bacillus subtilis var. niger (BG) endospores (used to simulate the spores of anthrax-causing Bacillus anthracis when testing bioaerosol sensors) and Penicillium brevicompactum fungal spores. It was found that 80–90% of initially “charge-neutralized” biological particles were removed from the air, when a small amount of ionization was generated in the electrostatic precipitator's (ESP) inlet and a precipitation voltage of ±4000V was applied across the agar plates. Over 70% of viable BG and P. brevicompactum spores entering the ESP were enumerated as colony forming units. The bioefficiency of the new sampler was about the same as that of the Biosampler, which was tested in parallel. In experiments with sensitive P. fluorescens vegetative cells, the ESP enumerated twice as many cells as the Biosampler. The latter result indicates that the electrostatic collection method may be especially useful for the collection and enumeration of sensitive Airborne Microorganisms. Experiments investigating the effect of aging time on the amount of electrical charge carried by the Airborne Microorganisms showed that the level of electrical charge gradually decreases with increasing aging time. However, even after the P. fluorescens cells had remained Airborne for an hour, they retained enough electrical charge to be collected with efficiency higher than 70%.