Microbial Aerosols Research Articles

Detection and analysis of fine particulate matter and microbial aerosol in chicken houses in Shandong Province, China

Bacteria and fungi are primary constituents of airborne microbes in fine particulate matter and harmful to health. To evaluate the environmental quality of different poultry houses in Shandong Province, China, the airborne aerobic bacteria, airborne fungi, and airborne Escherichia coli were collected by the Andersen-6 air microorganism sampler. The fine particulate matter was collected by a ZR-3920 ambient air particulate matter sampler, and bacterial and fungal diversities and relative abundances analyzed using high-throughput sequencing. Results showed that the concentrations of airborne aerobic bacteria, airborne fungi, and airborne Escherichia coli in poultry houses were 0.167 to 4.484 × 104 CFU/m3, 0.236 to 4.735 × 103 CFU/m3, and 0 to 33.0 CFU/m3, respectively. 11.4 to 34.3% of aerobic bacteria and 16.8 to 37.5% of fungi were distributed at levels 5 and 6 (0.6 to 2.1μm, the particle sizes similar to fine particulate matter) in the Andersen sampler. The concentration of fine particulate matter in the poultry houses was 114 to 230μg/m3, which was higher than the safety value 10 specified by WHO. In fine particulate matter, the main bacteria at phylum level were Firmicutes, Bacteroidetes, and Proteobacteria, whereas the dominant phylum of fungus was Ascomycota and Basidiomycota. Importantly, the relative abundances of Escherichia and Corynebacterium in the broiler houses were greater than those in layer houses. However, the percentages of Aspergillus and Penicillium were 13.5 and 0.56%, with a relatively high level in the layer houses. Altogether, results revealed that the ambient air quality in the poultry houses sampled had a relatively high abundance of conditional pathogenic bacteria and concentration of fine particulate matter, which could threaten the health of animals and workers in those environments.

Comparison of the Filter Efficiency of Medical Nonwoven Fabrics against Three Different Microbe Aerosols.

Exact evaluation of the performance of surgical masks and biohazard protective clothing materials against pathogens is important because it can provide helpful information that healthcare workers can use to select suitable materials to reduce infection risk. Currently, to evaluate the protective performance of nonwoven fabrics used in surgical masks against viral aerosols, a non-standardized test method using phi-X174 phage aerosols is widely performed because actual respiratory viruses pose an infection risk during testing and the phage is a safe virus to humans. This method of using a phage is simply modified from a standard method for evaluation of filter performance against bacterial aerosols using Staphylococcus aureus, which is larger than virus particles. However, it is necessary to perform such evaluations based on the size of the actual pathogen particles. Thus, we developed a new method that can be performed safely using inactivated viral particles and can quantitate the influenza virus in aerosols by antigen-capture ELISA (Shimasaki et al., 2016a) . In this study, we used three different microbial aerosols of phi-X174 phage, influenza virus, and S. aureus and tested the filter efficiency by capturing microbial aerosols for two medical nonwoven fabrics. We compared the filter efficiency against each airborne microbe to analyze the dependency of filter efficiency on the microbial particle size. Our results showed that against the three types of spherical microbe particles, the filter efficiencies against influenza virus particles were the lowest and those against phi-X174 phages were the highest for both types of nonwoven fabrics. The experimental results mostly corresponded with theoretical calculations. We conclude that the filter efficiency test using the phi-X174 phage aerosol may overestimate the protective performance of nonwoven fabrics with filter structure compared to that against real pathogens such as the influenza virus.

Measurements and modeling of surface–atmosphere exchange of microorganisms in Mediterranean grassland

Abstract. Microbial aerosols (mainly composed of bacterial and fungal cells) may constitute up to 74 % of the total aerosol volume. These biological aerosols are not only relevant to the dispersion of pathogens, but they also have geochemical implications. Some bacteria and fungi may, in fact, serve as cloud condensation or ice nuclei, potentially affecting cloud formation and precipitation and are active at higher temperatures compared to their inorganic counterparts. Simulations of the impact of microbial aerosols on climate are still hindered by the lack of information regarding their emissions from ground sources. This present work tackles this knowledge gap by (i) applying a rigorous micrometeorological approach to the estimation of microbial net fluxes above a Mediterranean grassland and (ii) developing a deterministic model (the PLAnET model) to estimate these emissions on the basis of a few meteorological parameters that are easy to obtain. The grassland is characterized by an abundance of positive net microbial fluxes and the model proves to be a promising tool capable of capturing the day-to-day variability in microbial fluxes with a relatively small bias and sufficient accuracy. PLAnET is still in its infancy and will benefit from future campaigns extending the available training dataset as well as the inclusion of ever more complex and critical phenomena triggering the emission of microbial aerosol (such as rainfall). The model itself is also adaptable as an emission module for dispersion and chemical transport models, allowing further exploration of the impact of land-cover-driven microbial aerosols on the atmosphere and climate.

Identifying virulence factor genes in E. coli in animal houses and their transmission to outside environments

Escherichia coli is a common bacterium in the air; it can affect the health of humans and animals. The carrying status of five primary virulence factor genes in E. coli (i.e., STa, STb, LTa, stx1, and stx2/stx2e) in various animal houses and their spread to the outside environment were investigated by comparing the air inside animal houses with that outside the houses. Multiplex polymerase chain reaction detection of the five genes was performed on samples from five chicken houses, and 117 E. coli isolates were obtained. From five swine houses, 120 were obtained, and from six cow houses, 143 were obtained. Results reveal that E. coli virulence genes derived from animal houses can be propagated via gas exchange from the inside to the outside and, depending on weather conditions, across some distance, resulting in biological pollution and the spread of pathogenic microorganisms. This study of the transmission of environmental microbial aerosols in animal houses has great significance in public health and epidemiology.

A high-flow portable biological aerosol trap (HighBioTrap) for rapid microbial detection

Bioaerosols exposure can lead to many adverse health effects and even result in death if highly infectious agents involved. Apparently, there is a great need for rapid detection of bioaerosols, for which air sampling often is the first critical step. However, currently available samplers often either require an external power and/or with low sampling flow rate, thus falling short of providing a practical solution when response time is of great concern.Here, we have designed and evaluated a new portable high volume bioaerosol sampler named as HighBioTrap through optimizing its operating parameters. The sampler was operated at a sampling flow rate of 1200L/min, with an impaction velocity of about 10.2m/s (S/W = 1.5, T/W = 1), while the weight of the sampler is about 1.9kg. The performances of the HighBioTrap sampler were tested both in lab controlled and natural environments (outdoor and indoor environments in a university building) along with the reference sampler-the BioStage impactor using aerosolized Polystyrene (PS) uniform microspheres of various sizes, aerosolized bacteria and also ambient air particles. The microbial community structures of collected culturable bacterial aerosol particles both by the HighBioTrap and the BioStage impactor in the natural environments were analyzed using gene sequence method.Experimental results with PS particles showed the HighBioTrap has a cutoff size of ~ 2µm. The widely used impactor design equation was found to be not applicable for predicting the performance of the HighBioTrap due to its large Reynolds number. When sampling aerosolized individual Pseudomonas fluorescens and Bacillus subtilis bacterial particles, the HighBioTrap had physical collection efficiencies of 10% and 20%, respectively. Despite the higher desiccation effects introduced by higher flow rate, the HighBioTrap was shown to obtain a higher microbial diversity than the BioStage impactor for both in outdoor and indoor environments given the same sampling time (p < 0.01). Our data also showed that most of the desiccation effects might have occurred between 3 and 5min of the sampling and an impaction velocity of around 10m/s might be a close-to-optimal impaction velocity for collecting most environmental bacterial aerosols while maximally preserving their culturability. This work contributes to our understanding of microbial sampling stress (impaction velocity and sampling time), while developing a portable high volume sampler. The HighBioTrap sampler could find its great efficiencies in qualitative microbial aerosol detection and analysis, such as investigation of microbial aerosol diversity for a particular environment, or when the low level of pathogens is present and detection time is of great concern.

Simultaneous improvement of waste gas purification and nitrogen removal using a novel aerated vertical flow constructed wetland

Insufficient oxygen supply is identified as one of the major factors limiting organic pollutant and nitrogen (N) removal in constructed wetlands (CWs). This study designed a novel aerated vertical flow constructed wetland (VFCW) using waste gas from biological wastewater treatment systems to improve pollutant removal in CWs, its potential in purifying waste gas was also identified. Compared with unaerated VFCW, the introduction of waste gas significantly improved NH4+-N and TN removal efficiencies by 128.48 ± 3.13% and 59.09 ± 2.26%, respectively. Furthermore, the waste gas ingredients, including H2S, NH3, greenhouse gas (N2O) and microbial aerosols, were remarkably reduced after passing through the VFCW. The removal efficiencies of H2S, NH3 and N2O were 77.78 ± 3.46%, 52.17 ± 2.53%, and 87.40 ± 3.89%, respectively. In addition, the bacterial and fungal aerosols in waste gas were effectively removed with removal efficiencies of 42.72 ± 3.21% and 47.89 ± 2.82%, respectively. Microbial analysis results revealed that the high microbial community abundance in the VFCW, caused by the introduction of waste gas from the sequencing batch reactor (SBR), led to its optimized nitrogen transformation processes. These results suggested that the VFCW intermittently aerated with waste gas may have potential application for purifying wastewater treatment plant effluent and waste gas, simultaneously.

Effect of electrical charges on potential of fibers for transport of microbial particles in dry and humid air

Coexistence of natural, synthetic or semi-synthetic fibers and microbial particles in aerosol state has not received so far a proper attention. In the scientific literature, there is almost no research devoted to fibrous aerosols as carriers of microbial particulates. The aim of this study was to assess the potential of natural and man-made fibers for airborne transport of electrically charged bacterial and fungal particles in different humidity conditions. The abilities of 4 natural (cotton, hemp, dog and horse hair) and 2 man-made (polyester and viscose) fibers to transport 7 microbial strains (Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Streptomyces albus, Cladosporium cladosporioides, Aspergillus versicolor and Penicillium melinii) in dry (RH < 30%) and humid (RH > 60%) air were analyzed in laboratory conditions using newly built aerosolization chamber. Each tested microbial aerosol was generated (for 10min) into the chamber from water suspension by Collison nebulizer (bacteria) or from contaminated agar surface using tube generator (fungi) and electrically charged or neutralized (–4500V, −3000V, −1500V, −500V, 0V, +500V, +1500V, +3000V, +4500V) using Topas electrostatic aerosol neutralizer. Bioaerosol concentrations were measured with Grimm optical particle counter. In the chamber, each tested microbial strain was mixed (for 10min) with respective studied fibers (their concentrations were controlled using 7400AD real-time fiber monitor) and such mixture was sampled with IOM cassette (for 5min at 5Lmin−1) on polycarbonate filter. After sampling, randomly selected samples were checked using scanning electron microscope to confirm the microbial presence on fibers. Then, all collected fibers carrying microbial particles were eluted by vortexing from the filter using 0.9% NaCl with Tween 80. Spread plate method was applied to assess culturable bacterial or fungal concentration in the resulted suspension.The quantitative assessment of electrically charged culturable microbial particles revealed that fibers were able to transport in the air up to 100 bacterial vegetative cells/spores or fungal conidia per 1 fiber. The most effective in this case were animal (dog and horse) and plant (cotton) fibers. Both tested man-made fibers were significantly less efficient than natural ones (p < 0.05). The study also showed that fraction of culturable microorganisms generated into the air and subsequently transported on fibers may reach 50% of total bioaerosol particles. In the environment of low air humidity (RH < 30%), the percentage of culturable microorganisms was always higher than those in high (RH > 60%) humidity conditions (p < 0.05). Moreover, the highest percentage of culturable microorganisms was always noted when the particles (bacterial vegetative cells or spores as well as fungal conidia) were electrically neutralized (0V). Each time when microbial particles were electrically charged (± 500–4500V), such process decreased the percentage of culturable bacteria and fungi (p < 0.05). This phenomenon can be explained by a disruptive influence of electrical conduction on viable microorganisms in the environment in which water is relatively easily available.

Onshore Wind Speed Modulates Microbial Aerosols along an Urban Waterfront

Wind blowing over aquatic and terrestrial surfaces produces aerosols, which include microbial aerosols. We studied the effect of onshore wind speeds on aerosol concentrations as well as total and culturable microbial aerosols (bacterial and viral) at an urban waterfront (New York, NY, United States of America). We used two distinct methods to characterize microbial aerosol responses to wind speed: A culture-based exposure-plate method measuring viable bacterial deposition near-shore (CFU accumulation rate); and a culture-independent aerosol sampler-based method measuring total bacterial and viral aerosols (cells m−3 air). While ambient coarse (&gt;2 µm) and fine (0.3–2 µm) aerosol particle number concentrations (regulated indicators of air quality) decreased with increasing onshore wind speeds, total and depositing culturable bacterial aerosols and total viral aerosols increased. Taxonomic identification of the 16S rDNA of bacterial aerosol isolates suggested both terrestrial and aquatic sources. Wind appears to increase microbial aerosol number concentrations in the near-shore environment by onshore transport at low wind speeds (&lt;4 m s−1), and increased local production and transport of new microbial aerosols from adjacent water surfaces at higher wind speeds (&gt;4 m s−1). This study demonstrates a wind-modulated microbial connection between water and air in the coastal urban environment, with implications for public health management and urban microbial ecology.

Microbiological Evaluation of Indoor Air Quality of State University Library

The present study was aimed at evaluating the number of bacteria and mould fungi in the indoor and outdoor environment of Imo University Library. The sampling sites were located in the rooms serving the functions typical of libraries (i.e. in the Main Reading Room, Current Periodicals Reading Room, Collections Conservation Laboratory, Old Prints Storeroom, in rooms serving other (non-library) functions (i.e. main hall, cafeteria, and toilet) as well as outside the library building. The analyses reveal that the concentrations of bacterial as well as fungal aerosols estimated with the use of the impaction method ranged between 10 1 -10 3 CFU·m -3 , which corresponds to the concentrations normally observed in areas of this kind. Evaluation of the hygienic condition of the studied areas was based on the criteria for microbiological cleanliness in interiors submitted by the European Commission in 1993. According to this classification, the air was considered to be heavily or moderately contaminated with bacteria, while the air contamination with mould fungi was described as low or moderate. The air in the Old Prints Storeroom was considered the least contaminated with microbial aerosol

Assessment of microbial aerosol emissions in an urban wastewater treatment plant operated with activated sludge process

Wastewater that enters wastewater treatment plants contains lots of pathogenic and nonpathogenic microorganisms which can become bioaerosols during treatment processes and pose health hazard to workers and nearby residents. The emission of the bioaerosols from an urban wastewater treatment plant in spring and summer in different locations and downwind of the plant adopting an extended mechanical aeration system was investigated. Samples of bacteria and fungi were collected within 6 months at 10 selected points by an Anderson one-stage impactor. The highest concentration of bacteria (mean 1373 CFU/m3, 741–2817 CFU/m3) and fungi (mean 1384 CFU/m3, 212–1610 CFU/m3) was found in downwind of the aeration basins. Statistical analysis showed a significant relationship between concentration of bacterial bioaerosols at downwind side of the aeration basins and wind speed (p value <0.05) and temperature (p value <0.05). Also, in the spring and summer, between the number of bacteria and fungi inside the plant and outside the plant (downwind) a significant correlation was observed (p value ≤0.05). The concentrations of bacteria at a distance of 500 m downwind were much higher than those at the background (upwind) point in spring and summer. The processes of wastewater treatment especially using mechanical equipment to create turbulence can be considered as a major source of spreading airborne microorganisms to ambient air of wastewater treatment plants, and the bioaerosols can be dispersed to downwind distances affecting the nearby neighboring. Therefore, in order to decrease the bioaerosols emission, doing some course of actions such as covering the surface of aeration basins, changing the aeration methods and aeration equipment (e. g using diffuser aerator) may be effective.

Seasonal Fluctuations of Microbial Aerosol in Live Poultry Markets and the Detection of Endotoxin.

Microbial aerosol whose species and concentrations are closely related to human health is ubiquitous. The effect of microbes on human and animal health and production performance is, in many cases, caused by the spreading of air. Samples in this experiment were from a live poultry market (LPM) in Tai’an, China, collected three times a day (8 am, 14 pm, and 20 pm) over three consecutive days each month for 11 months (Original sampling plan was a year, the government due to the environmental protection, the was LPM closed). The main indicators of the test were concentrations of cultural airborne bacteria, airborne fungi, and Gram-negative bacteria. At the same time the species of Gram-negative bacteria and the concentration of endotoxin were tested. Temperature and humidity were recorded in the process of each sampling. The results showed that the diurnal variation of the concentration of bacteria, fungi, and Gram-negative bacteria is higher in the morning and evening, but lower at noon. The concentrations of airborne bacteria and Gram-negative bacteria increased in earlier months and decreased in later months, with the peak appearing in the autumn. The concentration of fungi showed a decrease first and then tended to stabilize, with the peak occurring in the spring. The concentration peak of endotoxin occurred in the summer. Endotoxin levels were significantly correlated with humidity (r = 0.90, p < 0.01). Most bacteria were distributed at the third and fourth stages (2.1–4.7 μm) in the ANDERSEN-6 sampler. The dominant species of Gram-negative bacteria during the four seasons were Pseudomonas aeruginosa, Acinetobacter, Klebsiella pneumoniae, and Salmonella. In China, people have a habit of eating fresh poultry, LPM distribution is widespread, stream of people and traffic flow are large, easily caused the spread of bacteria and viruses, so the LPM microbial aerosol research have significant public health implications.

Fluorescent Bioaerosol Particles Resulting from Human Occupancy with and Without Respirators

Airborne transmission of pathogenic aerosols via human breath plays a major role in infectious disease outbreaks in indoor environments. Yet, their bioaerosol emission profiles are still not well quantified. Here, we first studied bioaerosol emission rates of human exhaled breath from 12 healthy subjects, and then evaluated the bioaerosol emissions when wearing two different respirators “Doctor masks” and N95 in a controlled environment (27 m3) using a bioaerosol sensor-ultraviolet aerodynamic particle spectrometer (UV-APS). The human bioaerosol contribution was further confirmed through classroom observation. The results showed that there was a peak around 1.5 µm for the fluorescent particles emitted from humans’ breath. For the controlled environment, the presence of 5 people without wearing masks increased bioaerosol concentration by 107% within 30 min at an average emission rate of 8.4 × 105 fluorescent particles person–1 hour–1 resulting from the occupancy. When wearing N95 masks or “Doctor masks”, bioaerosol increases were observed to be 81% or 31% for the controlled environment, respectively, lower compared to those without masks. In-classroom observation also showed a fluorescent particle concentration increase of about 50%. In all experiments, we observed a decline in PM number concentration. Bioaerosol emission from exhaled breath was calculated to account for about 17% of the increase in the controlled environment. The results here suggest the need for re-evaluating microbial aerosol exposure risks for medical sites that demand high levels of hygiene even while wearing a respirator.

Microbial aerosol in Beijing-Tianjin-Hebei region of Eastern China

With dense population, the Beijing-Tianjin-Hebei region of China is one of the regions most severely stricken by atmospheric pollution in the world. Research shows that the annual average concentration of airborne bacteria in this region is 1,380-3,020 CFU/m3. The concentration of gram-positive (G+) bacteria (80%-85%) is significantly higher than that of G− bacteria (15%-20%) and a total of 47 genera of bacteria are found. The number of airborne fungi in Beijing is 89-2,270 CFU/m3 and a total of nine genera of fungi are detected. Bacterial aerosols in the air are mostly distributed in particles bigger than 2 µm (82.2%). Fungal aerosols are mainly found in 1-6 µm particles, accounting for 71.6%, and are the most densely distributed in 2-3.5 µm particles. The regular changes in distribution region, time, and particle size of microbial aerosol in the air may provide an important research basis for the further study on the correlation between the quantity and genera of microorganisms in haze and human infectious disease.

Time-Dependent Size-Resolved Bacterial and Fungal Aerosols in Beijing Subway

ABSTRACTDespite of an important concern, human bioaerosol emission into subway is not well and directly characterized. Here, we used bioaerosol detector and next generation sequencing methods to investigate time-dependent bioaerosol size distributions in Beijing subway system between March and April, 2015. In contrast to weekends, weekday microbial aerosol results exhibited strong time dependence with higher bacterial and fungal aerosol levels up to 2083 CFU m–3 and 483 CFU m–3 observed, respectively, for the peak hours. During the peak hour (17:30–18:30), bioaerosol emissions at 0.8–3 µm was detected, while about three times higher concentration levels were observed compared to those during the off-peak hour (22:00–23:00). Similar bioaerosol size distributions were observed between ventilation outlets and subway platform air. During off-peak hours, subway bioaerosols had similar size distributions with the outside air. Sequence results revealed a vast array of airborne microbial species which varied from one station to another, but with Aspergillus spp. as dominant fungal species, and Staphylococcus, Pseudomonas as primary bacterial genera including human opportunistic ones. Our results provide direct online observations of human contributions to subway size-resolved bioaerosols, and enhancing ventilation system might help for controlling the exposure especially during the peak-hours.

Microbial aerosol in Beijing-Tianjin-Hebei region of Eastern China

With dense population, the Beijing-Tianjin-Hebei region of China is one of the regions most severely stricken by atmospheric pollution in the world. Research shows that the annual average concentration of airborne bacteria in this region is 1,380-3,020 CFU/m3. The concentration of gram-positive (G+) bacteria (80%-85%) is significantly higher than that of G&minus; bacteria (15%-20%) and a total of 47 genera of bacteria are found. The number of airborne fungi in Beijing is 89-2,270 CFU/m3 and a total of nine genera of fungi are detected. Bacterial aerosols in the air are mostly distributed in particles bigger than 2 µm (82.2%). Fungal aerosols are mainly found in 1-6 µm particles, accounting for 71.6%, and are the most densely distributed in 2-3.5 µm particles. The regular changes in distribution region, time, and particle size of microbial aerosol in the air may provide an important research basis for the further study on the correlation between the quantity and genera of microorganisms in haze and human infectious disease.

Culturable bioaerosols along an urban waterfront are primarily associated with coarse particles.

The source, characteristics and transport of viable microbial aerosols in urban centers are topics of significant environmental and public health concern. Recent studies have identified adjacent waterways, and especially polluted waterways, as an important source of microbial aerosols to urban air. The size of these aerosols influences how far they travel, their resistance to environmental stress, and their inhalation potential. In this study, we utilize a cascade impactor and aerosol particle monitor to characterize the size distribution of particles and culturable bacterial and fungal aerosols along the waterfront of a New York City embayment. We seek to address the potential contribution of bacterial aerosols from local sources and to determine how their number, size distribution, and taxonomic identity are affected by wind speed and wind direction (onshore vs. offshore). Total culturable microbial counts were higher under offshore winds (average of 778 CFU/m3 ± 67), with bacteria comprising the majority of colonies (58.5%), as compared to onshore winds (580 CFU/m3 ± 110) where fungi were dominant (87.7%). The majority of cultured bacteria and fungi sampled during both offshore winds (88%) and onshore winds (72%) were associated with coarse aerosols (>2.1 µm), indicative of production from local sources. There was a significant correlation (p < 0.05) of wind speed with both total and coarse culturable microbial aerosol concentrations. Taxonomic analysis, based on DNA sequencing, showed that Actinobacteria was the dominant phylum among aerosol isolates. In particular, Streptomyces and Bacillus, both spore forming genera that are often soil-associated, were abundant under both offshore and onshore wind conditions. Comparisons of bacterial communities present in the bioaerosol sequence libraries revealed that particle size played an important role in microbial aerosol taxonomy. Onshore and offshore coarse libraries were found to be most similar. This study demonstrates that the majority of culturable bacterial aerosols along a New York City waterfront were associated with coarse aerosol particles, highlighting the importance of local sources, and that the taxonomy of culturable aerosol bacteria differed by size fraction and wind direction.

Bioaerosol deposition on an air-conditioning cooling coil

This study is concerned with the role of a fin-and-tube heat exchanger in modifying microbial indoor air quality. Specifically, depositional losses of ambient bioaerosols and particles onto dry (not cooled) and wet (cool) coil surfaces were measured for different airspeeds passing through the test coil. Total, bacterial and fungal DNA concentrations in condensate water produced by a wet coil were also quantified by means of fluorescent dsDNA-binding dye and qPCR assays. Results revealed that the deposition of bioaerosols and total particles is substantial on coil surfaces, especially when wet and cool. The average deposition fraction was 0.14 for total DNA, 0.18 for bacterial DNA and 0.22 for fungal DNA on the dry coil, increasing to 0.51 for total DNA, 0.50 for bacterial DNA and 0.68 for fungal DNA on the wet coil. Overall, as expected, deposition fractions increased with increasing particle size and increasing airspeed. Deposited DNA was removed from the cooling coil surfaces through the flow of condensing water at a rate comparable to the rate of direct deposition from air. A downward trend of bacterial and fungal DNA measured in condensate water over time provides suggestive evidence of biological growth on heat exchangers during nonoperational times of a ventilation system. This investigation provides new information about bioaerosol deposition onto a conventional fin-and-tube cooling coil, a potentially important factor influencing indoor exposure to microbial aerosols in air-conditioned buildings.

Generic aspects of the airborne spread of human pathogens indoors and emerging air decontamination technologies.

Indoor air can be an important vehicle for a variety of human pathogens. This review provides examples of airborne transmission of infectious agents from experimental and field studies and discusses how airborne pathogens can contaminate other parts of the environment to give rise to secondary vehicles leading air-surface-air nexus with possible transmission to susceptible hosts. The following groups of human pathogens are covered because of their known or potential airborne spread: vegetative bacteria (staphylococci and legionellae), fungi (Aspergillus, Penicillium, and Cladosporium spp and Stachybotrys chartarum), enteric viruses (noro- and rotaviruses), respiratory viruses (influenza and coronaviruses), mycobacteria (tuberculous and nontuberculous), and bacterial spore formers (Clostridium difficile and Bacillus anthracis). An overview of methods for experimentally generating and recovering airborne human pathogens is included, along with a discussion of factors that influence microbial survival in indoor air. Available guidelines from the U.S. Environmental Protection Agency and other global regulatory bodies for the study of airborne pathogens are critically reviewed with particular reference to microbial surrogates that are recommended. Recent developments in experimental facilities to contaminate indoor air with microbial aerosols are presented, along with emerging technologies to decontaminate indoor air under field-relevant conditions. Furthermore, the role that air decontamination may play in reducing the contamination of environmental surfaces and its combined impact on interrupting the risk of pathogen spread in both domestic and institutional settings is discussed.

Effects of Microbial Aerosol in Poultry House on Meat Ducks' Immune Function.

The aim of this study was to evaluate effects of microbial aerosols on immune function of ducks and shed light on the establishment of microbial aerosol concentration standards for poultry. A total of 1800 1-d-old cherry valley ducks were randomly divided into five groups (A, B, C, D, and E) with 360 ducks in each. To obtain objective data, each group had three replications. Concentrations of airborne bacteria, fungi, endotoxin in different groups were created by controlling ventilation and bedding cleaning frequency. Group A was the control group and hygienic conditions deteriorated progressively from group B to E. A 6-stage Andersen impactor was used to detect the aerosol concentration of aerobes, gram-negative bacteria, fungi, and AGI-30 microbial air sampler detect the endotoxin, and Composite Gas Detector detect the noxious gas. In order to assess the immune function of meat ducks, immune indicators including H5 AIV antibody titer, IgG, IL-2, T-lymphocyte transformation rate, lysozyme and immune organ indexes were evaluated. Correlation coefficients were also calculated to evaluate the relationships among airborne bacteria, fungi, endotoxin, and immune indicators. The results showed that the concentration of airborne aerobe, gram-negative bacteria, fungi, endotoxin have a strong correlation to H5 AIV antibody titer, IgG, IL-2, T-lymphocyte transformation rate, lysozyme, and immune organ indexes, respectively. In addition, when the concentration of microbial aerosol reach the level of group D, serum IgG (6–8 weeks), lysozyme (4 week) were significantly higher than in group A (P < 0.05); serum IL-2 (7 and 8 weeks), T-lymphocyte transformation rate, lysozyme (7 and 8 weeks), spleen index (6 and 8 weeks), and bursa index (8 week) were significantly lower than in group A (P < 0.05 or P < 0.01). The results indicated that a high level of microbial aerosol adversely affected the immune level of meat ducks. The microbial aerosol values in group D provide a basis for recommending upper limit concentrations of microbial aerosols for healthy meat ducks.

Evaluation of disinfection efficiency in pet's hospital by using chlorine dioxide

Abstract Microbial aerosols could cause various human and animal health problems and their control is becoming a significant scientific and technological topic for consideration. The main objectives of this study were to monitor bioaerosol levels of the pet's hospital and then to perform disinfection efficiency by applying chlorine dioxide. The air quality within these pet's hospitals should satisfy the guidelines specified by the Taiwan Environmental Protection Administration (TEPA). Accordingly, this study performed an experimental investigation into the efficiency of two different gaseous chlorine dioxide (0.3 mg m−3) treatments in disinfecting a local pet's hospital, namely a single, one-off application and a multiple-daily application. In both cases, the ClO2 was applied using strategically-placed aerosol devices. The air quality before and after disinfection was evaluated by measuring the bioaerosol levels of bacteria and fungi. The experimental results found that the average background levels of bacteria and fungi prior to ClO2 disinfection were found to be 2014 ± 1350 and 1002 ± 669 CFU m−3, respectively. A single ClO2 application was found to total disinfected bacteria and fungi concentration levels by as much as 57.3 and 57.6%. By contrast, a multiple-daily ClO2 application was found to total disinfected bacteria and fungi concentration levels by as much as 65.1 and 57.6%. Among the two disinfection methods, the multiple-daily ClO2 application method was found to yield a higher disinfection efficiency for bacteria, i.e., 16.28 ± 0.92%. Thus, using a ClO2 disinfectant to maintain the air quality is of great importance to reduce infectious diseases in the pet's hospital. Therefore, the results suggest that the air quality guidelines prescribed by the TEPA for pet's hospital and other animal facilities can best be achieved by applying chlorine dioxide at regular intervals. The ClO2 aerosol devices can effectively restrain or disinfect airborne bacteria to improve the indoor air quality. Thus, it can be applied in pet's cosmetology institutions, hospitals, and other public areas, where bioaerosols are of great concern.