Size-resolved emission rates of airborne bacteria and fungi in an occupied classroom

Influence of housing characteristics on bacterial and fungal communities in homes of asthmatic children

Variations in home characteristics, such as moisture and occupancy, affect indoor microbial ecology as well as human exposure to microorganisms. Our objective was to determine how indoor bacterial and fungal community structure and diversity are associated with the broader home environment and its occupants. Next-generation DNA sequencing was used to describe fungal and bacterial communities in house dust sampled from 198 homes of asthmatic children in southern New England. Housing characteristics included number of people/children, level of urbanization, single/multifamily home, reported mold, reported water leaks, air conditioning (AC) use, and presence of pets. Both fungal and bacterial community structures were non-random and demonstrated species segregation (C-score, P < 0.00001). Increased microbial richness was associated with the presence of pets, water leaks, longer AC use, suburban (vs. urban) homes, and dust composition measures (P < 0.05). The most significant differences in community composition were observed for AC use and occupancy (people, children, and pets) characteristics. Occupant density measures were associated with beneficial bacterial taxa, including Lactobacillus johnsonii as measured by qPCR. A more complete knowledge of indoor microbial communities is useful for linking housing characteristics to human health outcomes. Microbial assemblies in house dust result, in part, from the building's physical and occupant characteristics.

Chamber bioaerosol study: human emissions of size-resolved fluorescent biological aerosol particles

Humans are a prominent source of airborne biological particles in occupied indoor spaces, but few studies have quantified human bioaerosol emissions. The chamber investigation reported here employs a fluorescence-based technique to evaluate bioaerosols with high temporal and particle size resolution. In a 75-m(3) chamber, occupant emission rates of coarse (2.5-10 μm) fluorescent biological aerosol particles (FBAPs) under seated, simulated office-work conditions averaged 0.9 ± 0.3 million particles per person-h. Walking was associated with a 5-6× increase in the emission rate. During both walking and sitting, 60-70% or more of emissions originated from the floor. The increase in emissions during walking (vs. while sitting) was mainly attributable to release of particles from the floor; the associated increased vigor of upper body movements also contributed. Clothing, or its frictional interaction with human skin, was demonstrated to be a source of coarse particles, and especially of the highly fluorescent fraction. Emission rates of FBAPs previously reported for lecture classes were well bounded by the experimental results obtained in this chamber study. In both settings, the size distribution of occupant FBAP emissions had a dominant mode in the 3-5 μm diameter range.

Microbiological Assessment of Indoor Air of Teaching Hospital Wards: A case of Jimma University Specialized Hospital

BACKGROUND

Hospital environment represents a congenial situation where microorganisms and susceptible patients are indoors together. Thus, the objective of this study is to provide fundamental data related to the microbial quality of indoor air of Jimma University Specialized Hospital wards, to estimate the health hazard and to create standards for indoor air quality control.

METHODS

The microbial quality of indoor air of seven wards of Jimma University Specialized Hospital was determined. Passive air sampling technique, using open Petri-dishes containing different culture media, was employed to collect sample twice daily.

RESULTS

The concentrations of bacteria and fungi aerosols in the indoor environment of the wards ranged between 2123 - 9733 CFU/m(3). The statistical analysis showed that the concentrations of bacteria that were measured in all studied wards were significantly different from each other (p-value=0.017), whereas the concentrations of fungi that were measured in all sampled wards were not significantly different from each other (p-value=0.850). Moreover, the concentrations of bacteria that were measured at different sampling time (morning and afternoon) were significantly different (p-value =0.001).

CONCLUSION

All wards that were included in the study were heavily contaminated with bacteria and fungi. Thus, immediate interventions are needed to control those environmental factors which favor the growth and multiplication of microbes, and it is vital to control visitors and students in and out the wards. Moreover, it is advisable that strict measures be put in place to check the increasing microbial load in the hospital environment.

Seasonal Dynamics of the Airborne Bacterial Community and Selected Viruses in a Children's Daycare Center

Children’s daycare centers appear to be hubs of respiratory infectious disease transmission, yet there is only limited information about the airborne microbial communities that are present in daycare centers. We have investigated the microbial community of the air in a daycare center, including seasonal dynamics in the bacterial community and the presence of specific viral pathogens. We collected filters from the heating, ventilation, and air conditioning (HVAC) system of a daycare center every two weeks over the course of a year. Amplifying and sequencing the 16S rRNA gene revealed that the air was dominated by Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes that are commonly associated with the human skin flora. Clear seasonal differences in the microbial community were not evident; however, the community structure differed when the daycare center was closed and unoccupied for a 13-day period. These results suggest that human occupancy, rather than the environment, is the major driver in shaping the microbial community structure in the air of the daycare center. Using PCR for targeted viruses, we detected a seasonal pattern in the presence of respiratory syncytial virus that included the period of typical occurrence of the disease related to the virus; however, we did not detect the presence of adenovirus or rotavirus at any time.

Indoor bioaerosol dynamics

Inhaling indoor air is the primary means by which humans are exposed to bioaerosols. Considering bacteria, fungi, and viruses, this study reviews the dynamic processes that govern indoor concentrations and fates of biological particulate material. Bioaerosol behavior is strongly coupled to particle size; this study emphasizes the range 0.1-10 μm in aerodynamic diameter. The principle of material balance allows concentrations to be determined from knowledge of important source and removal processes. Sources reviewed here include outdoor air introduced by air exchange plus indoor emission from occupants, occupant activities, and moldy materials. Important mechanisms that remove bioaerosols from indoor air include air exchange, deposition onto indoor surfaces, and active filtration. The review summarizes knowledge about size-dependent particle deposition in different regions of the respiratory tract, techniques for measuring indoor bioaerosols, and evidence for diseases caused by airborne exposure to bioaerosols. Future research challenges and opportunities are highlighted.

Roles of the human occupant in indoor chemistry

Over the last decade, influences of the human occupant on indoor chemistry have been investigated in environments ranging from simulated aircraft cabins to actual classrooms. We have learned that ozone reacts rapidly with constituents of skin surface lipids on exposed skin, hair, and clothing, substantially reducing indoor ozone concentrations but increasing airborne levels of mono- and bifunctional compounds that contain carbonyl, carboxyl, or α-hydroxy ketone groups. Moreover, occupants transfer skin oils to and shed skin flakes (desquamation) onto indoor surfaces. Evidence for the presence of skin flakes/oils has been found in airborne particles, settled dust, and wipes of indoor surfaces. These occupant residues are also anticipated to scavenge ozone and produce byproducts. Under typical conditions, occupancy is anticipated to decrease the net level of oxidants in indoor air. When occupants scavenge ozone, the level of SOA derived from ozone/terpene chemistry decreases; the fraction of SVOCs in the gas-phase increases, and the fraction associated with airborne particles decreases. Occupants also remove organic compounds, including certain chemically active species, via bodily intake. Studies reviewed in this paper demonstrate the pronounced influences of humans on chemistry within the spaces they inhabit and the consequences of these influences on their subsequent chemical exposures.

Sources of airborne microorganisms in the built environment

Each day people are exposed to millions of bioaerosols, including whole microorganisms, which can have both beneficial and detrimental effects. The next chapter in understanding the airborne microbiome of the built environment is characterizing the various sources of airborne microorganisms and the relative contribution of each. We have identified the following eight major categories of sources of airborne bacteria, viruses, and fungi in the built environment: humans; pets; plants; plumbing systems; heating, ventilation, and air-conditioning systems; mold; dust resuspension; and the outdoor environment. Certain species are associated with certain sources, but the full potential of source characterization and source apportionment has not yet been realized. Ideally, future studies will quantify detailed emission rates of microorganisms from each source and will identify the relative contribution of each source to the indoor air microbiome. This information could then be used to probe fundamental relationships between specific sources and human health, to design interventions to improve building health and human health, or even to provide evidence for forensic investigations.

The microbiome of the built environment and mental health

The microbiome of the built environment (MoBE) is a relatively new area of study. While some knowledge has been gained regarding impacts of the MoBE on the human microbiome and disease vulnerability, there is little knowledge of the impacts of the MoBE on mental health. Depending on the specific microbial species involved, the transfer of microorganisms from the built environment to occupant's cutaneous or mucosal membranes has the potential to increase or disrupt immunoregulation and/or exaggerate or suppress inflammation. Preclinical evidence highlighting the influence of the microbiota on systemic inflammation supports the assertion that microorganisms, including those originating from the built environment, have the potential to either increase or decrease the risk of inflammation-induced psychiatric conditions and their symptom severity. With advanced understanding of both the ecology of the built environment, and its influence on the human microbiome, it may be possible to develop bioinformed strategies for management of the built environment to promote mental health. Here we present a brief summary of microbiome research in both areas and highlight two interdependencies including the following: (1) effects of the MoBE on the human microbiome and (2) potential opportunities for manipulation of the MoBE in order to improve mental health. In addition, we propose future research directions including strategies for assessment of changes in the microbiome of common areas of built environments shared by multiple human occupants, and associated cohort-level changes in the mental health of those who spend time in the buildings. Overall, our understanding of the fields of both the MoBE and influence of host-associated microorganisms on mental health are advancing at a rapid pace and, if linked, could offer considerable benefit to health and wellness.

Microbial aerosol liberation from soiled textiles isolated during routine residuals handling in a modern health care setting

BACKGROUND

A wide variety of specialty textiles are used in health care settings for bedding, clothing, and privacy. The ability of textiles to host or otherwise sequester microbes has been well documented; however, their reciprocal potential for liberating airborne bacteria remains poorly characterized. In response, a multi-season survey of bacterial bioaerosols was conducted in the origin and terminus of residual paths which are specifically designed to isolate soiled hospital textiles as they are moved to laundering. This survey used conventional optical particle counting which incorporated multi-channel fluorescence in conjunction with molecular phylogenetic analyses to characterize the bioaerosols liberated during soiled textile storage--immediately before and after the occupation of a modern hospital. Although outfitted with a HEPA filtration system, the number of airborne particles presenting fluorescing optical signatures consistent with airborne bacteria and fungi significantly increased in textile holding rooms soon after the hospital's commissioning, even though these isolated residual areas rarely host personnel. The bioaerosol liberated during textile storage was characterized using Illumina MiSeq sequencing of bacterial 16S ribosomal ribonucleic acid (rRNA) genes. Gene copies recovered by quantitative PCR from aerosol collected in co-located impingers were consistent with fluorescence gated optical particle counting.

RESULTS

The relative abundance patterns of proximal bacterial bioaerosol were such that the air in the origin and terminus of textile storage rooms could not be differentiated once the hospital began processing soiled linens. Genes from microbes typically associating with human skin, feces, and hair--Staphylococcus, Propionibacteria, Corynebacteria, Lactobacillus, and Streptococcus spp.--dominated the aerosol abundance profiles in textile holding rooms, which were generally far less diverse than communities recovered from surfaces in patient rooms.

CONCLUSIONS

These results suggest that aerosol partitioning from the routine handling of soiled textiles can contribute to airborne exposures in the health care environment.

Concentration and determinants of molds and allergens in indoor air and house dust of French dwellings

Molds and allergens are common indoor biocontaminants. The aims of this study were to assess the concentrations of common molds in indoor air and floor dust and the concentrations of house dust mite, cat and dog allergens in mattress dust in French dwellings, and to assess predictors of these concentrations. A sample of 150 houses in Brittany (western France) was investigated. Airborne Cladosporium and Penicillium were detected in more than 90% of the dwellings, Aspergillus in 46% and Alternaria in only 6% of the housings. Regarding floor dust samples, Cladosporium and Penicillium were detected in 92 and 80% of the housings respectively, Aspergillus in 49% and Alternaria in 14%. House dust mite allergens Der p1 and Der f1 were detected in 90% and 77% of the mattress dust samples respectively and Can f1 and Fel d1 in 37% and 89% of the homes. Airborne and dustborne mold concentrations, although not statistically correlated (except for Aspergillus) shared most of their predictors. Multivariate linear models for mold levels, explaining up to 62% of the variability, showed an influence of the season, of the age of the dwelling, of aeration habits, presence of pets, smoking, signals of dampness, temperature and relative humidity. Allergens in the dust of the mattress were strongly related to the presence of pets and cleaning practices of bedsheets, these factors accounting for 60% of the variability. This study highlights ubiquitous contamination by molds and underlines complex interaction between outdoor and indoor sources and factors.

Characterizing airborne fungal and bacterial concentrations and emission rates in six occupied children's classrooms

Baseline information on size-resolved bacterial, fungal, and particulate matter (PM) indoor air concentrations and emission rates is presented for six school classrooms sampled in four countries. Human occupancy resulted in significantly elevated airborne bacterial (81 times on average), fungal (15 times), and PM mass (nine times) concentrations as compared to vacant conditions. Occupied indoor/outdoor (I/O) ratios consistently exceeded vacant I/O ratios. Regarding size distributions, average room-occupied bacterial, fungal, and PM geometric mean particle sizes were similar to one another while geometric means estimated for bacteria, fungi, and PM mass during vacant sampling were consistently lower than when occupied. Occupancy also resulted in elevated indoor bacterial-to-PM mass-based and number-based ratios above corresponding outdoor levels. Mean emission rates due to human occupancy were 14 million cells/person/h for bacteria, 14 million spore equivalents/person/h for fungi, and 22 mg/person/h for PM mass. Across all locations, indoor emissions contributed 83 ± 27% (bacteria), 66 ± 19% (fungi), and 83 ± 24% (PM mass) of the average indoor air concentrations during occupied times.

PRACTICAL IMPLICATIONS

An extensive data set of bacterial and fungal size-distributed indoor air concentrations and emission rates is presented. Analysis of these data contributes to an understanding of how indoor bacterial and fungal aerosols are influenced by human occupancy. This work extends beyond prior culture and DNA-based microbiome studies in buildings to include quantitative relationships between size-resolved bacterial and fungal concentrations in indoor air and building parameters such as occupancy, ventilation, and outdoor conditions. The work indicates that occupancy-associated emissions (e.g., via resuspension and shedding) contribute more to both bacterial and fungal indoor air concentrations than do outdoor sources for the occupied classrooms investigated in this study.

The first microbial environment of infants born by C-section: the operating room microbes

BACKGROUND

Newborns delivered by C-section acquire human skin microbes just after birth, but the sources remain unknown. We hypothesized that the operating room (OR) environment contains human skin bacteria that could be seeding C-section born infants.

RESULTS

To test this hypothesis, we sampled 11 sites in four operating rooms from three hospitals in two cities. Following a C-section procedure, we swabbed OR floors, walls, ventilation grids, armrests, and lamps. We sequenced the V4 region of the 16S rRNA gene of 44 samples using Illumina MiSeq platform. Sequences were analyzed using the QIIME pipeline. Only 68 % of the samples (30/44, >1000 sequences per site) yielded sufficient DNA reads to be analyzed. The bacterial content of OR dust corresponded to human skin bacteria, with dominance of Staphylococcus and Corynebacterium. Diversity of bacteria was the highest in the ventilation grids and walls but was also present on top of the surgery lamps. Beta diversity analyses showed OR dust bacterial content clustering first by city and then by hospital (t test using unweighted UniFrac distances, p < 0.05).

CONCLUSIONS

We conclude that the dust from ORs, collected right after a C-section procedure, contains deposits of human skin bacteria. The OR microbiota is the first environment for C-section newborns, and OR microbes might be seeding the microbiome in these babies. Further studies are required to identify how this OR microbiome exposure contributes to the seeding of the neonatal microbiome. The results might be relevant to infant health, if the current increase in risk of immune and metabolic diseases in industrialized societies is related to lack of natural exposure to the vaginal microbiome during labor and birth.

Protocol Improvements for Low Concentration DNA-Based Bioaerosol Sampling and Analysis

INTRODUCTION

As bioaerosol research attracts increasing attention, there is a need for additional efforts that focus on method development to deal with different environmental samples. Bioaerosol environmental samples typically have very low biomass concentrations in the air, which often leaves researchers with limited options in choosing the downstream analysis steps, especially when culture-independent methods are intended.

OBJECTIVES

This study investigates the impacts of three important factors that can influence the performance of culture-independent DNA-based analysis in dealing with bioaerosol environmental samples engaged in this study. The factors are: 1) enhanced high temperature sonication during DNA extraction; 2) effect of sampling duration on DNA recoverability; and 3) an alternative method for concentrating composite samples. In this study, DNA extracted from samples was analysed using the Qubit fluorometer (for direct total DNA measurement) and quantitative polymerase chain reaction (qPCR).

RESULTS AND FINDINGS

The findings suggest that additional lysis from high temperature sonication is crucial: DNA yields from both high and low biomass samples increased up to 600% when the protocol included 30-min sonication at 65°C. Long air sampling duration on a filter media was shown to have a negative impact on DNA recoverability with up to 98% of DNA lost over a 20-h sampling period. Pooling DNA from separate samples during extraction was proven to be feasible with margins of error below 30%.

Humans differ in their personal microbial cloud

Dispersal of microbes between humans and the built environment can occur through direct contact with surfaces or through airborne release; the latter mechanism remains poorly understood. Humans emit upwards of 10⁶ biological particles per hour, and have long been known to transmit pathogens to other individuals and to indoor surfaces. However it has not previously been demonstrated that humans emit a detectible microbial cloud into surrounding indoor air, nor whether such clouds are sufficiently differentiated to allow the identification of individual occupants. We used high-throughput sequencing of 16S rRNA genes to characterize the airborne bacterial contribution of a single person sitting in a sanitized custom experimental climate chamber. We compared that to air sampled in an adjacent, identical, unoccupied chamber, as well as to supply and exhaust air sources. Additionally, we assessed microbial communities in settled particles surrounding each occupant, to investigate the potential long-term fate of airborne microbial emissions. Most occupants could be clearly detected by their airborne bacterial emissions, as well as their contribution to settled particles, within 1.5–4 h. Bacterial clouds from the occupants were statistically distinct, allowing the identification of some individual occupants. Our results confirm that an occupied space is microbially distinct from an unoccupied one, and demonstrate for the first time that individuals release their own personalized microbial cloud.

Microbiome interplay: plants alter microbial abundance and diversity within the built environment

The built indoor microbiome has importance for human health. Residents leave their microbial fingerprint but nothing is known about the transfer from plants. Our hypothesis that indoor plants contribute substantially to the microbial abundance and diversity in the built environment was experimentally confirmed as proof of principle by analyzing the microbiome of the spider plant Chlorophytum comosum in relation to their surroundings. The abundance of Archaea, Bacteria, and Eukaryota (fungi) increased on surrounding floor and wall surfaces within 6 months of plant isolation in a cleaned indoor environment, whereas the microbial abundance on plant leaves and indoor air remained stable. We observed a microbiome shift: the bacterial diversity on surfaces increased significantly but fungal diversity decreased. The majority of cells were intact at the time of samplings and thus most probably alive including diverse Archaea as yet unknown phyllosphere inhabitants. LEfSe and network analysis showed that most microbes were dispersed from plant leaves to the surrounding surfaces. This led to an increase of specific taxa including spore-forming fungi with potential allergic potential but also beneficial plant-associated bacteria, e.g., Paenibacillus. This study demonstrates for the first time that plants can alter the microbiome of a built environment, which supports the significance of plants and provides insights into the complex interplay of plants, microbiomes and human beings.

Cleanroom Maintenance Significantly Reduces Abundance but Not Diversity of Indoor Microbiomes

Cleanrooms have been considered microbially-reduced environments and are used to protect human health and industrial product assembly. However, recent analyses have deciphered a rather broad diversity of microbes in cleanrooms, whose origin as well as physiological status has not been fully understood. Here, we examined the input of intact microbial cells from a surrounding built environment into a spacecraft assembly cleanroom by applying a molecular viability assay based on propidium monoazide (PMA). The controlled cleanroom (CCR) was characterized by ~6.2*10³ 16S rRNA gene copies of intact bacterial cells per m² floor surface, which only represented 1% of the total community that could be captured via molecular assays without viability marker. This was in contrast to the uncontrolled adjoining facility (UAF) that had 12 times more living bacteria. Regarding diversity measures retrieved from 16S rRNA Illumina-tag analyzes, we observed, however, only a minor drop in the cleanroom facility allowing the conclusion that the number but not the diversity of microbes is strongly affected by cleaning procedures. Network analyses allowed tracking a substantial input of living microbes to the cleanroom and a potential enrichment of survival specialists like bacterial spore formers and archaeal halophiles and mesophiles. Moreover, the cleanroom harbored a unique community including 11 exclusive genera, e.g., Haloferax and Sporosarcina, which are herein suggested as indicators of cleanroom environments. In sum, our findings provide evidence that archaea are alive in cleanrooms and that cleaning efforts and cleanroom maintenance substantially decrease the number but not the diversity of indoor microbiomes.

Chamber bioaerosol study: outdoor air and human occupants as sources of indoor airborne microbes

Human occupants are an important source of microbes in indoor environments. In this study, we used DNA sequencing of filter samples to assess the fungal and bacterial composition of air in an environmental chamber under different levels of occupancy, activity, and exposed or covered carpeting. In this office-like, mechanically ventilated environment, results showed a strong influence of outdoor-derived particles, with the indoor microbial composition tracking that of outdoor air for the 2-hour sampling periods. The number of occupants and their activity played a significant but smaller role influencing the composition of indoor bioaerosols. Human-associated taxa were observed but were not particularly abundant, except in the case of one fungus that appeared to be transported into the chamber on the clothing of a study participant. Overall, this study revealed a smaller signature of human body-associated taxa than had been expected based on recent studies of indoor microbiomes, suggesting that occupants may not exert a strong influence on bioaerosol microbial composition in a space that, like many offices, is well ventilated with air that is moderately filtered and moderately occupied.

Metagenomic insights into the bioaerosols in the indoor and outdoor environments of childcare facilities

Airborne microorganisms have significant effects on human health, and children are more vulnerable to pathogens and allergens than adults. However, little is known about the microbial communities in the air of childcare facilities. Here, we analyzed the bacterial and fungal communities in 50 air samples collected from five daycare centers and five elementary schools located in Seoul, Korea using culture-independent high-throughput pyrosequencing. The microbial communities contained a wide variety of taxa not previously identified in child daycare centers and schools. Moreover, the dominant species differed from those reported in previous studies using culture-dependent methods. The well-known fungi detected in previous culture-based studies (Alternaria, Aspergillus, Penicillium, and Cladosporium) represented less than 12% of the total sequence reads. The composition of the fungal and bacterial communities in the indoor air differed greatly with regard to the source of the microorganisms. The bacterial community in the indoor air appeared to contain diverse bacteria associated with both humans and the outside environment. In contrast, the fungal community was largely derived from the surrounding outdoor environment and not from human activity. The profile of the microorganisms in bioaerosols identified in this study provides the fundamental knowledge needed to develop public health policies regarding the monitoring and management of indoor air quality.

Indoor emissions as a primary source of airborne allergenic fungal particles in classrooms

This study quantifies the influence of ventilation and indoor emissions on concentrations and particle sizes of airborne indoor allergenic fungal taxa and further examines geographical variability, each of which may affect personal exposures to allergenic fungi. Quantitative PCR and multiplexed DNA sequencing were employed to count and identify allergenic fungal aerosol particles indoors and outdoors in seven school classrooms in four different countries. Quantitative diversity analysis was combined with building characterization and mass balance modeling to apportion source contributions of indoor allergenic airborne fungal particles. Mass balance calculations indicate that 70% of indoor fungal aerosol particles and 80% of airborne allergenic fungal taxa were associated with indoor emissions; on average, 81% of allergenic fungi from indoor sources originated from occupant-generated emissions. Principal coordinate analysis revealed geographical variations in fungal communities among sites in China, Europe, and North America (p < 0.05, analysis of similarity), demonstrating that geography may also affect personal exposures to allergenic fungi. Indoor emissions including those released with occupancy contribute more substantially to allergenic fungal exposures in classrooms sampled than do outdoor contributions from ventilation. The results suggest that design and maintenance of buildings to control indoor emissions may enable reduced indoor inhalation exposures to fungal allergens.

Indoor fungi: companions and contaminants

This review discusses the role of fungi and fungal products in indoor environments, especially as agents of human exposure. Fungi are present everywhere, and knowledge for indoor environments is extensive on their occurrence and ecology, concentrations, and determinants. Problems of dampness and mold have dominated the discussion on indoor fungi. However, the role of fungi in human health is still not well understood. In this review, we take a look back to integrate what cultivation-based research has taught us alongside more recent work with cultivation-independent techniques. We attempt to summarize what is known today and to point out where more data is needed for risk assessment associated with indoor fungal exposures. New data have demonstrated qualitative and quantitative richness of fungal material inside and outside buildings. Research on mycotoxins shows that just as microbes are everywhere in our indoor environments, so too are their metabolic products. Assessment of fungal exposures is notoriously challenging due to the numerous factors that contribute to the variation of fungal concentrations in indoor environments. We also may have to acknowledge and incorporate into our understanding the complexity of interactions between multiple biological agents in assessing their effects on human health and well-being.

Key determinants of the fungal and bacterial microbiomes in homes

BACKGROUND

The microbiome of the home is of great interest because of its possible impact on health. Our goal was to identify some of the factors that determine the richness, evenness and diversity of the home's fungal and bacterial microbiomes.

METHOD

Vacuumed settled dust from homes (n=35) in Cincinnati, OH, were analyzed by pyrosequencing to determine the fungal and bacterial relative sequence occurrence. The correlation coefficients between home environmental characteristics, including age of home, Environmental Relative Moldiness Index (ERMI) values, occupant number, relative humidity and temperature, as well as pets (dog and cat) were evaluated for their influence on fungal and bacterial communities. In addition, linear discriminant analysis (LDA) was used for identifying fungal and bacterial genera and species associated with those housing determinants found to be significant.

RESULTS

The fungal richness was found to be positively correlated with age of home (p=0.002), ERMI value (p=0.003), and relative humidity (p=0.015) in the home. However, fungal evenness and diversity were only correlated with the age of home (p=0.001). Diversity and evenness (not richness) of the bacterial microbiome in the homes were associated with dog ownership. Linear discriminant analysis showed total of 39 putative fungal genera/species with significantly higher LDA scores in high ERMI homes and 47 genera/species with significantly higher LDA scores in homes with high relative humidity. When categorized according to the age of the home, a total of 67 fungal genera/species had LDA scores above the significance threshold. Dog ownership appeared to have the most influence on the bacterial microbiome, since a total of 130 bacterial genera/species had significantly higher LDA scores in homes with dogs.

CONCLUSIONS

Some key determinants of the fungal and bacterial microbiome appear to be excess moisture, age of the home and dog ownership.

Evaluation of a high efficiency cabin air (HECA) filtration system for reducing particulate pollutants inside school buses

An increasing number of studies have reported deleterious health effects of vehicle-emitted particulate matter (PM), including PM2.5 (aerodynamic diameter≤2.5 μm), black carbon (BC), and ultrafine particles (UFPs, diameter≤100 nm). When commuting inside school buses, children are exposed to high level of these pollutants due to emissions from both school bus itself and other on-road vehicles. This study developed an on-board high efficiency cabin air (HECA) filtration system for reducing children's exposure inside school buses. Six school buses were driven on two typical routes to evaluate to what extent the system reduces particulate pollutant levels inside the buses. The testing routes included freeways and major arterial roadways in Los Angeles, CA. UFP number concentrations and size distributions as well as BC and PM2.5 concentrations were monitored concurrently inside and outside of each bus. With the HECA filtration system on, in-cabin UFP and BC levels were reduced by 88±6% and 84±5% on averages across all driving conditions, respectively. The system was less effective for PM2.5 (55±22%) but successfully kept its levels below 12 μg/m3 inside all the buses. For all three types of particulate pollutants, in-cabin reductions were higher on freeways than on arterial roadways.

Quo vadis? Microbial profiling revealed strong effects of cleanroom maintenance and routes of contamination in indoor environments

Space agencies maintain highly controlled cleanrooms to ensure the demands of planetary protection. To study potential effects of microbiome control, we analyzed microbial communities in two particulate-controlled cleanrooms (ISO 5 and ISO 8) and two vicinal uncontrolled areas (office, changing room) by cultivation and 16S rRNA gene amplicon analysis (cloning, pyrotagsequencing, and PhyloChip G3 analysis). Maintenance procedures affected the microbiome on total abundance and microbial community structure concerning richness, diversity and relative abundance of certain taxa. Cleanroom areas were found to be mainly predominated by potentially human-associated bacteria; archaeal signatures were detected in every area. Results indicate that microorganisms were mainly spread from the changing room (68%) into the cleanrooms, potentially carried along with human activity. The numbers of colony forming units were reduced by up to ~400 fold from the uncontrolled areas towards the ISO 5 cleanroom, accompanied with a reduction of the living portion of microorganisms from 45% (changing area) to 1% of total 16S rRNA gene signatures as revealed via propidium monoazide treatment of the samples. Our results demonstrate the strong effects of cleanroom maintenance on microbial communities in indoor environments and can be used to improve the design and operation of biologically controlled cleanrooms.

Impacts of flood damage on airborne bacteria and fungi in homes after the 2013 Colorado Front Range flood

Flood-damaged homes typically have elevated microbial loads, and their occupants have an increased incidence of allergies, asthma, and other respiratory ailments, yet the microbial communities in these homes remain under-studied. Using culture-independent approaches, we characterized bacterial and fungal communities in homes in Boulder, CO, USA 2-3 months after the historic September, 2013 flooding event. We collected passive air samples from basements in 50 homes (36 flood-damaged, 14 non-flooded), and we sequenced the bacterial 16S rRNA gene (V4-V5 region) and the fungal ITS1 region from these samples for community analyses. Quantitative PCR was used to estimate the abundances of bacteria and fungi in the passive air samples. Results indicate significant differences in bacterial and fungal community composition between flooded and non-flooded homes. Fungal abundances were estimated to be three times higher in flooded, relative to non-flooded homes, but there were no significant differences in bacterial abundances. Penicillium (fungi) and Pseudomonadaceae and Enterobacteriaceae (bacteria) were among the most abundant taxa in flooded homes. Our results suggest that bacterial and fungal communities continue to be affected by flooding, even after relative humidity has returned to baseline levels and remediation has removed any visible evidence of flood damage.

Spatial and temporal variations in indoor environmental conditions, human occupancy, and operational characteristics in a new hospital building

The dynamics of indoor environmental conditions, human occupancy, and operational characteristics of buildings influence human comfort and indoor environmental quality, including the survival and progression of microbial communities. A suite of continuous, long-term environmental and operational parameters were measured in ten patient rooms and two nurse stations in a new hospital building in Chicago, IL to characterize the indoor environment in which microbial samples were taken for the Hospital Microbiome Project. Measurements included environmental conditions (indoor dry-bulb temperature, relative humidity, humidity ratio, and illuminance) in the patient rooms and nurse stations; differential pressure between the patient rooms and hallways; surrogate measures for human occupancy and activity in the patient rooms using both indoor air CO₂ concentrations and infrared doorway beam-break counters; and outdoor air fractions in the heating, ventilating, and air-conditioning systems serving the sampled spaces. Measurements were made at 5-minute intervals over consecutive days for nearly one year, providing a total of ∼8×10⁶ data points. Indoor temperature, illuminance, and human occupancy/activity were all weakly correlated between rooms, while relative humidity, humidity ratio, and outdoor air fractions showed strong temporal (seasonal) patterns and strong spatial correlations between rooms. Differential pressure measurements confirmed that all patient rooms were operated at neutral pressure. The patient rooms averaged about 100 combined entrances and exits per day, which suggests they were relatively lightly occupied compared to higher traffic environments (e.g., retail buildings) and more similar to lower traffic office environments. There were also clear differences in several environmental parameters before and after the hospital was occupied with patients and staff. Characterizing and understanding factors that influence these building dynamics is vital for hospital environments, where they can impact patient health and the survival and spread of healthcare associated infections.

Metagenomic analysis of the airborne environment in urban spaces

The organisms in aerosol microenvironments, especially densely populated urban areas, are relevant to maintenance of public health and detection of potential epidemic or biothreat agents. To examine aerosolized microorganisms in this environment, we performed sequencing on the material from an urban aerosol surveillance program. Whole metagenome sequencing was applied to DNA extracted from air filters obtained during periods from each of the four seasons. The composition of bacteria, plants, fungi, invertebrates, and viruses demonstrated distinct temporal shifts. Bacillus thuringiensis serovar kurstaki was detected in samples known to be exposed to aerosolized spores, illustrating the potential utility of this approach for identification of intentionally introduced microbial agents. Together, these data demonstrate the temporally dependent metagenomic complexity of urban aerosols and the potential of genomic analytical techniques for biosurveillance and monitoring of threats to public health.

Chamber bioaerosol study: outdoor air and human occupants as sources of indoor airborne microbes

Human occupants are an important source of microbes in indoor environments. In this study, we used DNA sequencing of filter samples to assess the fungal and bacterial composition of air in an environmental chamber under different levels of occupancy, activity, and exposed or covered carpeting. In this office-like, mechanically ventilated environment, results showed a strong influence of outdoor-derived particles, with the indoor microbial composition tracking that of outdoor air for the 2-hour sampling periods. The number of occupants and their activity played a significant but smaller role influencing the composition of indoor bioaerosols. Human-associated taxa were observed but were not particularly abundant, except in the case of one fungus that appeared to be transported into the chamber on the clothing of a study participant. Overall, this study revealed a smaller signature of human body-associated taxa than had been expected based on recent studies of indoor microbiomes, suggesting that occupants may not exert a strong influence on bioaerosol microbial composition in a space that, like many offices, is well ventilated with air that is moderately filtered and moderately occupied.

Total Virus and Bacteria Concentrations in Indoor and Outdoor Air

Viruses play important roles in microbial ecology and some infectious diseases, but relatively little is known about concentrations, sources, transformation, and fate of viruses in the atmosphere. We have measured total airborne concentrations of virus-like and bacteria-like particles (VLPs between 0.02 μm and 0.5 μm in size and BLPs between 0.5 μm and 5 μm) in nine locations: a classroom, a daycare center, a dining facility, a health center, three houses, an office, and outdoors. Indoor concentrations of both VLPs and BLPs were ~10⁵ particles m^-3, and the virus-to-bacteria ratio was 0.9 ± 0.1 (mean ± standard deviation across different locations). There were no significant differences in concentration between different indoor environments. VLP and BLP concentrations in outdoor air were 2.6 and 1.6 times higher, respectively, than in indoor air. At the single outdoor site, the virus-to-bacteria ratio was 1.4.

Size-resolved fluorescent biological aerosol particle concentrations and occupant emissions in a university classroom

This study is among the first to apply laser-induced fluorescence to characterize bioaerosols at high time and size resolution in an occupied, common-use indoor environment. Using an ultraviolet aerodynamic particle sizer, we characterized total and fluorescent biological aerosol particle (FBAP) levels (1-15 μm diameter) in a classroom, sampling with 5-min resolution continuously during eighteen occupied and eight unoccupied days distributed throughout a one-year period. A material-balance model was applied to quantify per-person FBAP emission rates as a function of particle size. Day-to-day and seasonal changes in FBAP number concentration (NF ) values in the classroom were small compared to the variability within a day that was attributable to variable levels of occupancy, occupant activities, and the operational state of the ventilation system. Occupancy conditions characteristic of lecture classes were associated with mean NF source strengths of 2 × 10(6) particles/h/person, and 9 × 10(4) particles per metabolic g CO2 . During transitions between lectures, occupant activity was more vigorous, and estimated mean, per-person NF emissions were 0.8 × 10(6) particles per transition. The observed classroom peak in FBAP size at 3-4 μm is similar to the peak in fluorescent and biological aerosols reported from several studies outdoors.

PRACTICAL IMPLICATIONS

Coarse particles that exhibit fluorescence at characteristic wavelengths are considered to be proxies for biological particles. Recently developed instruments permit their detection and sizing in real time. In a mechanically ventilated classroom, emissions from human occupants were a strong determinant of coarse-mode fluorescent biological aerosol particle (FBAP) levels. Human FBAP emission rates were significant under quiet occupancy conditions and increased with activity level. Fluorescent particle emissions peaked at a diameter of 3–4 μm, which is the expected modal size of airborne particles with associated microbes. Human activity patterns, and associated coarse FBAP and total particle levels varied strongly on short timescales. Thus, the dynamic temporal behavior of aerosol concentrations must be considered when determining collection protocols for samples meant to be representative of average concentrations using time-integrated or ‘snapshot’ bioaerosol measurement techniques.

Microbiological quality of indoor air in university libraries

OBJECTIVE

To evaluate the concentration of bacteria and fungi in the indoor environment of Jimma University libraries, so as to estimate the health hazard and to create standards for indoor air quality control.

METHODS

The microbial quality of indoor air of eight libraries of Jimma University was determined. The settle plate method using open Petri-dishes containing different culture media was employed to collect sample twice daily. Isolates were identified according to standard methods.

RESULTS

The concentrations of bacteria and fungi aerosols in the indoor environment of the university libraries ranged between 367-2595 CFU/m(3). According to the sanitary standards classification of European Commission, almost all the libraries indoor air of Jimma University was heavily contaminated with bacteria and fungi. In spite of their major source difference, the average fungi density found in the indoor air of libraries did appear to follow the same trend with bacterial density (P=0.001). The bacteria isolates included Micrococcus sp., Staphylococcus aureus, Streptococcus pyogenes, Bacillus sp. and Neisseria sp. while Cladosporium sp., Alternaria sp., Penicillium sp. and Aspergillus sp. were the most isolated fungi.

CONCLUSIONS

The indoor air of all libraries were in the range above highly contaminated according to European Commission classification and the most isolates are considered as potential candidates involved in the establishment of sick building syndromes and often associated with clinical manifestations like allergy, rhinitis, asthma and conjunctivitis. Thus, attention must be given to control those environmental factors which favor the growth and multiplication of microbes in indoor environment of libraries to safeguard the health of users and workers.

Indoor-air microbiome in an urban subway network: diversity and dynamics

Subway systems are indispensable for urban societies, but microbiological characteristics of subway aerosols are relatively unknown. Previous studies investigating microbial compositions in subways employed methodologies that underestimated the diversity of microbial exposure for commuters, with little focus on factors governing subway air microbiology, which may have public health implications. Here, a culture-independent approach unraveling the bacterial diversity within the urban subway network in Hong Kong is presented. Aerosol samples from multiple subway lines and outdoor locations were collected. Targeting the 16S rRNA gene V4 region, extensive taxonomic diversity was found, with the most common bacterial genera in the subway environment among those associated with skin. Overall, subway lines harbored different phylogenetic communities based on α- and β-diversity comparisons, and closer inspection suggests that each community within a line is dependent on architectural characteristics, nearby outdoor microbiomes, and connectedness with other lines. Microbial diversities and assemblages also varied depending on the day sampled, as well as the time of day, and changes in microbial communities between peak and nonpeak commuting hours were attributed largely to increases in skin-associated genera in peak samples. Microbial diversities within the subway were influenced by temperature and relative humidity, while carbon dioxide levels showed a positive correlation with abundances of commuter-associated genera. This Hong Kong data set and communities from previous studies conducted in the United States formed distinct community clusters, indicating that additional work is required to unravel the mechanisms that shape subway microbiomes around the globe.

Indoor air quality in Brazilian universities

This study evaluated the indoor air quality in Brazilian universities by comparing thirty air-conditioned (AC) (n = 15) and naturally ventilated (NV) (n = 15) classrooms. The parameters of interest were indoor carbon dioxide (CO₂), temperature, relative humidity (RH), wind speed, viable mold, and airborne dust levels. The NV rooms had larger concentration of mold than the AC rooms (1001.30 ± 125.16 and 367.00 ± 88.13 cfu/m³, respectively). The average indoor airborne dust concentration exceeded the Brazilian standards (<80 μg/m³) in both NV and AC classrooms. The levels of CO₂ in the AC rooms were significantly different from the NV rooms (1433.62 ± 252.80 and 520.12 ± 37.25 ppm, respectively). The indoor air quality in Brazilian university classrooms affects the health of students. Therefore, indoor air pollution needs to be considered as an important public health problem.

'Core species' in three sources of indoor air belonging to the human micro-environment to the exclusion of outdoor air

Although we spend the majority of our lives indoors, the airborne microbial content of enclosed spaces still remains inadequately described. The objective of this study was to characterize the bacterial diversity of indoor air in three different enclosed spaces with three levels of occupancy, and, in particular, to highlight the 'core' species, the opportunistic pathogens and their origins. Our findings provide an overall description of bacterial diversity in these indoor environments. Data gathered from the three enclosed spaces revealed the presence of a common indoor signature (60% of total sequences in common). This work will provide a clearer understanding of the dominant groups of bacteria encountered in enclosed spaces: Actinobacteria, Proteobacteria, Firmicutes and Bacteroidetes. Thus, certain evidence revealed a connection between 'core' species and the human micro-environment (20% of phylotypes and 12% of sequences of human origin). Overall PCA analysis showed that the indoor environment is influenced mainly by the microbial diversity from nose and skin. Among the 'core species' found during this study, a large number (72% of all pathogen-related sequences were concentrated in 'core species') of genera and species are known to be responsible for opportunistic or nosocomial diseases or to include human commensal bacteria such as Mycobacterium sp., Acinetobacter baumanii, Aerococcus viridians, Thermoactinomyces vulgaris or Clostridium perfringens.

Challenges of studying viral aerosol metagenomics and communities in comparison with bacterial and fungal aerosols

Despite the obvious importance of viral transmission and ecology to medicine, epidemiology, ecology, agriculture, and microbiology, the study of viral bioaerosols and community structure has remained a vastly underexplored area, due to both unresolved technical challenges and unrecognized importance. High-throughput, culture-independent techniques such as viral metagenomics are beginning to revolutionize the study of viral ecology. With recent developments in viral metagenomics, characterization of viral bioaerosol communities provides an opportunity for high-impact future research. However, there remain significant challenges for the study of viral bioaerosols compared with viruses in other matrices, such as water, the human gut, and soil. Collecting enough biomass is essential for successful metagenomic analysis, but this is a challenge with viral bioaerosols. Herein, we provide a perspective on the importance of studying viral bioaerosols, the challenges of studying viral community structure, and the potential opportunities for improvements in methods to study viruses in indoor and outdoor air.

Hand bacterial communities vary across two different human populations

This study utilized pyrosequencing-based phylogenetic library results to assess bacterial communities on the hands of women in Tanzania and compared these communities with bacteria assemblages on the hands of US women. Bacterial population profiles and phylogenetically based ordinate analysis demonstrated that the bacterial communities on hands were more similar for selected populations within a country than between the two countries considered. Organisms that have commonly been identified in prior human skin microbiome studies, including members of the Propionibacteriaceae, Staphylococcaceae and Streptococceacea families, were highly abundant on US hands and drove the clustering of US hand microbial communities into a distinct group. The most abundant bacterial taxa on Tanzanian hands were the soil-associated Rhodobacteraceae and Nocardioidaceae. These results help to expand human microbiome results beyond US and European populations, and the identification and abundance of soil-associated bacteria on Tanzanian hands demonstrated the important role of the environment in shaping the microbial communities on human hands.

Bacterial communities on classroom surfaces vary with human contact

BACKGROUND

Humans can spend the majority of their time indoors, but little is known about the interactions between the human and built-environment microbiomes or the forces that drive microbial community assembly in the built environment. We sampled 16S rRNA genes from four different surface types throughout a university classroom to determine whether bacterial assemblages on each surface were best predicted by routine human interactions or by proximity to other surfaces within the classroom. We then analyzed our data with publicly-available datasets representing potential source environments.

RESULTS

Bacterial assemblages from the four surface types, as well as individual taxa, were indicative of different source pools related to the type of human contact each surface routinely encounters. Spatial proximity to other surfaces in the classroom did not predict community composition.

CONCLUSIONS

Our results indicate that human-associated microbial communities can be transferred to indoor surfaces following contact, and that such transmission is possible even when contact is indirect, but that proximity to other surfaces in the classroom does not influence community composition.

An evaluation of the infection control potential of a UV clinical podiatry unit

BACKGROUND

Infection control is a key issue in podiatry as it is in all forms of clinical practice. Airborne contamination may be particularly important in podiatry due to the generation of particulates during treatment. Consequently, technologies that prevent contamination in podiatry settings may have a useful role. The aims of this investigation were twofold, firstly to determine the ability of a UV cabinet to protect instruments from airborne contamination and secondly to determine its ability to remove microbes from contaminated surfaces and instruments.

METHOD

A UV instrument cabinet was installed in a University podiatry suite. Impact samplers and standard microbiological techniques were used to determine the nature and extent of microbial airborne contamination. Sterile filters were used to determine the ability of the UV cabinet to protect exposed surfaces. Artificially contaminated instruments were used to determine the ability of the cabinet to remove microbial contamination.

RESULTS

Airborne bacterial contamination was dominated by Gram positive cocci including Staphylococcus aureus. Airborne fungal levels were much lower than those observed for bacteria. The UV cabinet significantly reduced (p < 0.05) the observed levels of airborne contamination. When challenged with contaminated instruments the cabinet was able to reduce microbial levels by between 60% to 100% with more complex instruments e.g. clippers, remaining contaminated.

CONCLUSIONS

Bacterial airborne contamination is a potential infection risk in podiatry settings due to the presence of S. aureus. The use of a UV instrument cabinet can reduce the risk of contamination by airborne microbes. The UV cabinet tested was unable to decontaminate instruments and as such could pose an infection risk if misused.

Indoor airborne bacterial communities are influenced by ventilation, occupancy, and outdoor air source

Architects and engineers are beginning to consider a new dimension of indoor air: the structure and composition of airborne microbial communities. A first step in this emerging field is to understand the forces that shape the diversity of bioaerosols across space and time within the built environment. In an effort to elucidate the relative influences of three likely drivers of indoor bioaerosol diversity - variation in outdoor bioaerosols, ventilation strategy, and occupancy load - we conducted an intensive temporal study of indoor airborne bacterial communities in a high-traffic university building with a hybrid HVAC (mechanically and naturally ventilated) system. Indoor air communities closely tracked outdoor air communities, but human-associated bacterial genera were more than twice as abundant in indoor air compared with outdoor air. Ventilation had a demonstrated effect on indoor airborne bacterial community composition; changes in outdoor air communities were detected inside following a time lag associated with differing ventilation strategies relevant to modern building design. Our results indicate that both occupancy patterns and ventilation strategies are important for understanding airborne microbial community dynamics in the built environment.

Stability of airborne microbes in the Louvre Museum over time

The microbial content of air has as yet been little described, despite its public health implications, and there remains a lack of environmental microbial data on airborne microflora in enclosed spaces. In this context, the aim of this study was to characterize the diversity and dynamics of airborne microorganisms in the Louvre Museum using high-throughput molecular tools and to underline the microbial signature of indoor air in this human-occupied environment. This microbial community was monitored for 6 month during occupied time. The quantitative results revealed variations in the concentrations of less than one logarithm, with average values of 10(3) and 10(4) Escherichia coli/Aspergillus fumigatus genome equivalent per m(3) for bacteria and fungi, respectively. Our observations highlight the stability of the indoor airborne bacterial diversity over time, while the corresponding eukaryote community was less stable. Bacterial diversity characterized by pyrosequencing 454 showed high diversity dominated by the Proteobacteria which represented 51.1%, 46.9%, and 38.4% of sequences, for each of the three air samples sequenced. A common bacterial diversity was underlined, corresponding to 58.4% of the sequences. The core species were belonging mostly to the Proteobacteria and Actinobacteria, and to the genus Paracoccus spp., Acinetobacter sp., Pseudomonas sp., Enhydrobacter sp., Sphingomonas sp., Staphylococcus sp., and Streptococcus sp.

Architectural design drives the biogeography of indoor bacterial communities

BACKGROUND

Architectural design has the potential to influence the microbiology of the built environment, with implications for human health and well-being, but the impact of design on the microbial biogeography of buildings remains poorly understood. In this study we combined microbiological data with information on the function, form, and organization of spaces from a classroom and office building to understand how design choices influence the biogeography of the built environment microbiome.

RESULTS

Sequencing of the bacterial 16S gene from dust samples revealed that indoor bacterial communities were extremely diverse, containing more than 32,750 OTUs (operational taxonomic units, 97% sequence similarity cutoff), but most communities were dominated by Proteobacteria, Firmicutes, and Deinococci. Architectural design characteristics related to space type, building arrangement, human use and movement, and ventilation source had a large influence on the structure of bacterial communities. Restrooms contained bacterial communities that were highly distinct from all other rooms, and spaces with high human occupant diversity and a high degree of connectedness to other spaces via ventilation or human movement contained a distinct set of bacterial taxa when compared to spaces with low occupant diversity and low connectedness. Within offices, the source of ventilation air had the greatest effect on bacterial community structure.

CONCLUSIONS

Our study indicates that humans have a guiding impact on the microbial biodiversity in buildings, both indirectly through the effects of architectural design on microbial community structure, and more directly through the effects of human occupancy and use patterns on the microbes found in different spaces and space types. The impact of design decisions in structuring the indoor microbiome offers the possibility to use ecological knowledge to shape our buildings in a way that will select for an indoor microbiome that promotes our health and well-being.

Size-selective assessment of agricultural workers' personal exposure to airborne fungi and fungal fragments

Fungi are ubiquitous agents that cause human respiratory diseases. Very few studies have size-selectively assessed farmers' exposure to fungi and fungal fragments in agricultural settings. In this study, a two-stage bio-aerosol cyclone personal sampler was employed to collect airborne fungi and fungal fragments size-selectively at corn, swine, poultry, and mushroom farms. The collected air samples were analyzed for culturable fungi, fungal spores, viable fungi and (1 → 3)-β-D-glucan. The results show that the median concentrations ranged from 3.2 × 10(5) to 1.3 × 10(8)spores/m(3) for total fungal spores, from 1.3 × 10(5) to 5.1 × 10(7)spores/m(3) for total viable fungi, from 1.9 × 10(3) to 1.5 × 10(7)CFU/m(3) for total culturable fungi, and from 4.3 × 10(3) to 2.4 × 10(6)pg/m(3) for total (1 → 3)-β-D-glucan. The aerodynamic sizes of most of the collected fungal contaminants were larger than 1.8 μm. Total (1 → 3)-β-D-glucan significantly correlated with total fungal spores (r = 0.65, p < 0.001), total viable fungi (r = 0.68, p < 0.001) and total culturable fungi (r = 0.72, p < 0.001). Total (1 → 3)-β-D-glucan significantly correlated with Aspergillus/Penicillium, Alternaria, and Cladosporium. Alternaria and Botrytis were also found to highly correlate with (1 → 3)-β-D-glucan at the size <1 μm, which was less than the expected spore sizes (the mean measured aerodynamic sizes were 18.5 μm for Alternaria and 6.1 μm for Botrytis); therefore, Alternaria and Botrytis might release small fragments that could enter the deep lung and cause respiratory diseases.

Environmental and ventilation assessment in Child Day Care Centers in Porto: the ENVIRH Project

Children attending day care centers (CDCC) have been reported to be more prone to infectious diseases when compared with those cared for at home, and are exposed to conditions that may increase the risk of allergies and asthma. Several studies revealed that consequences of poor ventilation conditions include high levels of carbon dioxide (CO2) and many other indoor pollutants commonly detected in schools. Nine child day care centers were selected randomly to participate in this study. Fifty-two classrooms were assessed for chemical, biological, physical, and allergen parameters in spring and winter seasons in these nine CDCC located in Porto, Portugal. Outdoor measurements were also conducted for comparison. Our results indicated that (i) particulate matter (PM10) median levels were above the national reference levels, both by classroom type and by season; (ii) TVOC kindergarten peak values may raise some concern; (iii) CO2 was present at high median and maximum levels during spring and winter assessment in both nurseries and kindergartens classrooms; (iv) total bacteria concentrations were 57- and 52-fold higher in the nursery and kindergarten than outdoors, respectively, for the spring season; (v) winter and spring median predicted mean vote (PMV) indices were between "neutral" (0) and "slightly cool" (≤ -1) in the thermal sensation scale for comfort situations (-2 to 2) for both types of classrooms; (vi) there were significant differences for both PMV and predicted percentage of dissatisfied (PPD) indices by season; and (vii) CO2, total bacteria, and gram-negative bacteria were associated with low airflow rates. These data will help to evaluate the effectiveness of current building operation practices in child day care centers regarding indoor air quality and respiratory health.

Indoor aerosols: from personal exposure to risk assessment

Motivated by growing considerations of the scale, severity, and risks associated with human exposure to indoor particulate matter, this work reviewed existing literature to: (i) identify state-of-the-art experimental techniques used for personal exposure assessment; (ii) compare exposure levels reported for domestic/school settings in different countries (excluding exposure to environmental tobacco smoke and particulate matter from biomass cooking in developing countries); (iii) assess the contribution of outdoor background vs indoor sources to personal exposure; and (iv) examine scientific understanding of the risks posed by personal exposure to indoor aerosols. Limited studies assessing integrated daily residential exposure to just one particle size fraction, ultrafine particles, show that the contribution of indoor sources ranged from 19% to 76%. This indicates a strong dependence on resident activities, source events and site specificity, and highlights the importance of indoor sources for total personal exposure. Further, it was assessed that 10-30% of the total burden of disease from particulate matter exposure was due to indoor-generated particles, signifying that indoor environments are likely to be a dominant environmental factor affecting human health. However, due to challenges associated with conducting epidemiological assessments, the role of indoor-generated particles has not been fully acknowledged, and improved exposure/risk assessment methods are still needed, together with a serious focus on exposure control.

Characterization of the monthly variation in (1 → 3)-β-D-glucan concentrations in university laboratories

We characterize the monthly variation in (1 → 3)-β-D-glucan concentration measured over the course of 1 year, and we evaluate the characteristics of size selection using a two-stage cyclone sampler. The (1 → 3)-β-D-glucan concentrations were measured in four bio-related laboratories. A total of 156 samples were collected using a new two-stage cyclone sampler. Analysis of (1 → 3)-β-D-glucan was performed using the kinetic Limulus amebocyte lysate assay. The study showed that airborne (1 → 3)-β-D-glucan concentrations were significantly higher in laboratory D (mean ± SD 1,105 ± 1,893 pg/m(3)) and in the spring (5,458 pg/m(3)). The highest concentration of (1 → 3)-β-D-glucan occurred in the spring, particularly in May.

The ignored diversity: complex bacterial communities in intensive care units revealed by 16S pyrosequencing

Indoor microbial communities play an important role in everyday human health, especially in the intensive care units (ICUs) of hospitals. We used amplicon pyrosequencing to study the ICU microbiome and were able to detect diverse sequences, in comparison to the currently used standard cultivation technique that only detected 2.5% of the total bacterial diversity. The phylogenetic spectrum combined species associated with the outside environment, taxa closely related to potential human pathogens, and beneficials as well as included 7 phyla and 76 genera. In addition, Propionibacterium spp., Pseudomonas spp., and Burkholderia spp. were identified as important sources of infections. Despite significantly different bacterial area profiles for floors, medical devices, and workplaces, similarities by network analyses and strains with identical molecular fingerprints were detected. This information will allow for new assessment of public health risks in ICUs, help create new sanitation protocols, and further our understanding of the development of hospital-acquired infections.