Airborne fungal spores in 80 homes in the Latrobe Valley, Australia: levels, seasonality and indoor-outdoor relationship

Airborne viable and total fungal spores were sampled inside and outside 80 houses in the Latrobe Valley, Victoria, Australia as part of a larger indoor environmental study. Each residence was visited six times over a period of 1 year for sample collection, and fungal spore samples were collected from at least three indoor sites and from an outdoor site. Viable spores were sampled using an Andersen sampler, while total spores were assessed using a Burkard spore trap. Identification of fungal colonies to genera level was performed in two seasons; winter and late spring. The most common fungal genera/groups wereCladosporium, Penicillium, and yeasts, both indoors and outdoors in winter and late spring. Outdoor levels were higher than those indoors throughout the year, and a significant seasonal variation in spore levels was seen both indoors and outdoors with overall maxima in summer. Contrary to this trend, the levels ofAspergillus, yeasts,Cephalosporium andGliocladium were higher in winter. Most fungal genera were found in greater concentrations outdoors compared to indoors, butPenicillium was more common indoors. Outdoor spore levels were a significant influence on indoor levels, but seasonal differences suggest that other influences are important.     

Airborne bacteria and fungal spores in the indoor environment. A case study in Singapore

The concentration of airborne fungal spores and bacteria as related to room temperature, humidity and occupancy levels within a library building in Singapore was determined. Measurement of indoor air quality with respect to microorganisms is of particular importance in tropical environments due to the extensive use of air‐conditioning systems and the potential implications for human health. This study has revealed a number of interesting relationships between the concentrations of fungal spores and bacteria in relation to both environmental and human factors. The levels of fungal spores measured in the indoor environment were approximately fifty times lower than those measured outside, probably because of the lowered humidity caused by air‐conditioning in the indoor environment. The variation in fungal spore concentration in the outdoor environment is likely to be due to the diurnal periodicity of spore release and the response to environmental factors such as light temperature and humidity. The indoor concentration of fungal spores in air was not clearly correlated to concentrations measured in air outside of the library building and remained relatively constant, unaffected by the difference in the numbers of occupants in the library. In contrast, the indoor concentrations of bacteria in air were approximately ten times higher than those measured outdoors, indicating a signficant internal source of bacteria. The elevated levels of indoor bacteria were primarily attributed to the number of library occupants. Increased human shedding of skin cells, ejection of microorganisms and particulates from the respiratory tract, and the transport of bacteria on suspended dust particles from floor surfaces probably accounts for the strong positive correlation between occupancy levels and the concentration of bacteria in internal air.     

Viable and not viable spore concentrations in National Gallery of Umbria (Italy)

The conservation actions towards artworks holding a common patrimony for the community are of primary importance, but also those related to their "container" as museums, libraries or archives are to consider. Fungal spores and bacteria carried by air flows to the artwork surface can colonize it causing biodeterioration through physical and/or chemical alterations of the materials with the irreversible loss of their value. The quality control of the indoor air surrounding the historic building is essential, as well as for the protection and conservation of the artwork, also for the protection of the health of operators and visitors. The aim of this study was to monitor airborne fungal particles, through volumetric spore traps, for improving the knowledge about the conservation and protection of artworks in the museum environment analysing the principal relationships between indoor environmental conditions and potentially biodeteriogen fungal spore growth. The evidence of no significant relationships between spore concentrations and environmental conditions recorded inside the different expositive rooms testified the regular and correct maintenance of the air conditioning system inside the considered building (National Gallery of Umbria, central Italy). Moreover, in a specific museum room a significant spore concentration decreasing trend was recorded mainly due to a structural modification in the same building.

     

Pollen and fungal spore sampling and analysis. Statistical evaluations

Statistical evaluations of samples obtained from a Burkard seven-day recording volumetric pollen/spore trap were performed to determine the precision of the sampling and analysis procedures. The reproducibility of co-located traps was also investigated. The results showed that pollen grain transect counting was not significantly different, while fungal spore counting produced statistically different results. There was no statistical difference in the number of pollen and fungal spores counted between the co-located samplers. Reasons for the differences in the fungal spore counts are presented.     

Do indoor plants contribute to the aeromycota in city buildings?

Many studies have focused on the sources of fungal contamination in indoor spaces. Pathogenic fungi have been detected in the potting mix of indoor plants; however, it is unclear if plants in indoor work spaces make qualitative or quantitative contributions to the aeromycota within buildings. The current work represents a field study to determine, under realistic office conditions, whether indoor plants make a contribution to the airborne aeromycota. Fifty-five offices, within two buildings in Sydney’s central business district, were studied over two seasonal periods: autumn and spring. We found that indoor plant presence made no significant difference to either indoor mould spore counts or their species composition. No seasonal differences occurred between autumn and spring samples. Indoor spore loads were significantly lower than outdoor levels, demonstrating the efficiency of the heating, ventilation and air conditioning systems in the buildings sampled. Neither the number of plants nor the species of plant used had an influence on spore loads; however, variations of those two variables offer potential for further studies. We conclude that conservative numbers of indoor plants make no substantial contribution to building occupants exposure to fungi.     

An assessment of the air quality in indoor and outdoor air with reference to fungal spores and pollen grains in four working environments in Kerala, India

Qualitative and quantitative analyses of airborne fungal spores and pollen grains in four working environments (market, saw mill, poultry and cow sheds) in Thiruvananthapuram, the capital city of Kerala, India, were carried out for 2 years using Burkard Personal Slide Sampler and Andersen Two-Stage Sampler. Total spore concentration in these sites was always higher in indoor environments than in outdoor environments. Difference in concentration was not statistically significant in any of these work places except in saw mill (t test, p < 0.05). The highest spore concentration was recorded here followed by market, poultry and cow sheds. A total of 32 fungal spore types from indoor environments and 33 spore types from outdoor environments were recorded. Of them, 16 spore types were common to all the sites. Ameropsores, Cladosporium, other basidiospores, Ganoderma and Nigrospora were the dominant spore types in both indoor and outdoor environments. A total of 27 species of viable fungi from indoor and 24 species from outdoor environments were identified. Penicillium citrinum, Aspergillus flavus and Aspergillus niger were the most dominant viable fungi isolated. In contrast, total pollen concentration was always higher in outdoor environments than in indoor environments. Twenty-nine pollen types from indoor and 32 pollen types from outdoor were captured during the sampling. Poaceae, Cocos, Artocarpus, Amaranthus/Chenopodium and Tridax were the common and dominant pollen types observed in all the sites. Peak spore and pollen incidence were recorded during the late rainy and dry seasons (October–February) in both indoor and outdoor environments. The study revealed high prevalence of predominantly allergenic fungal spores and pollen grains in all the four work places. Workers/visitors are at potential risk of susceptibility to respiratory/allergic disorders.     

Incidence and remediation of fungi in a sick building in Malaysia: a case study

Problems caused by indoor microbial, especially fungal growth, have been further exaggerated by the increased incidence of water intrusions, condensation from air-conditioning system, and other factors. While fungal contamination in a building can be one of the indicators of indoor air quality (IAQ), air quality assessment and remediation should be considered as important and should be carried out systematically. This study reports the incidence and remediation of an excessive fungal growth in a building in Universiti Sains Malaysia (USM), Pulau Pinang, Malaysia. Acting on an official report by the building owner and occupants, an immediate walk-through investigation was carried out between June and December 2009. A thorough sampling comprising swab and spore impactor techniques showed that the colony-forming unit per cubic meter of air (CFU/m³) levels were far above those in the guidelines of most developed countries. Thus, the building was declared a ‘sick building’ and closed to the publics. However, through immediate action with recommended methods to overcome the problem, the premise has been pronounced safe. This is a good example of successful teamwork that involved a continuous investigation by a team of experts along with comprehensive action taken by the occupants and other authorities responsible for the building.     

Airborne fungal spores in a sawmill environment in Palakkad District, Kerala, India

Concentration of airborne fungal spores inindoor and outdoor environments of a sawmill in Palakkad district of Kerala, India was studied with Burkard Personal Slide Sampler from January to December 1997. Total spore concentration in the indoor and outdoor showed a 3:2 ratio. Higher spore count was observed in indoor in January and in outdoor in October. Thirty three fungal spore types were identified from the indoor and twenty six from the outdoor. Aspergillus/Penicillium, Cladosporium, Nigrospora, Ganoderma, `other basidiospores' and ascospores were the dominant components of the airspora. Aspergillus/Penicillium, the most dominant spore type in the indoor contributed 51.19% and Cladosporium, the most dominant spore type in the outdoor contributed 44.75% of the total spores. The study revealed high prevalence of predominantly allergenic fungal spores in the sawmill environment.     

Aerobiological monitoring of Aspergillus/Penicillium spores during the potato storage

Aerobiological studies are widely used to determine the fungal spectrum in the air. These studies have revealed that Aspergillus/Penicillium spores are the most abundant spores in both outdoor and indoor environments. In this study, we have presented the variations in the concentration of these spores in an indoor environment (a potato store). Aerobiological sampling was conducted during five storage period (from 2002 to 2008 year) using a Hirst-type spore trap. The maximum spore concentrations were counted during the second fortnight of January and in the months of February and March, with values higher than 6,000 spores/m³ per day. A correlation analysis between the Aspergillus/Penicillium spores and the main environmental parameters was performed; significant coefficients were obtained for spores present in the store previous days and mean temperature of the same day and previous days (P < 0.001). Moreover, a regression model was established and predicted 53% variability of the data included in the analysis. The best obtained model took into account the Aspergillus/Penicillium spore type levels of 1 previous day and the mean temperature in the preceding 2 days.     

Study of airborne fungal spores in Madrid, Spain

The concentration of fungal spores in the atmosphere of Madrid was recorded and analyzed for the year 2003. Airborne spores were sampled continuously with a Hirst-type spore trap located on the roof of a building of the School of Pharmacy, at about 8 m above ground level. Correlation between the mean daily spore concentrations and meteorological variables were explored by means of Spearman’s correlation analyses. Seventy spore types were identified, of which the most numerous were Cladosporium, Aspergillaceae (conidia), Coprinus, Agaricales (basidiospores), Ustilago (teliospores) and Pleospora (ascospores). These six types of spores represented more than 70% of the total. Cladosporium represented 41% of the total fungal spores, while Ustilago spores, the concentrations of which in May and June exceeded 47% of the monthly total spore count, constituted the second most important group. Spores reached their highest concentrations in the spring months, and in the autumn, mainly in October. A␣positive significant correlation was found between airborne spore counts and temperature and relative humidity. The results provide a picture of the spectrum of airborne fungal spores present in the atmosphere of Madrid and of the `peak' periods of their presence. Future studies will provide more detailed information on the seasonal dynamics of the spores most frequently found in the air as well as on the extent to which atmospheric conditions influence their release, dispersion and sedimentation processes.     

The incidence of fungal spores in the ambient air and inside homes: Evidence from London

Little research has been carried out in London concerning fungal spore prevalence yet this information may help to elucidate geographical patterns of asthma and hay fever. Although many types of spore reach peak concentrations outdoors in late-summer, the incidences in the indoor environment may be more important through the winter because of heating and poor ventilation. Daily average concentrations of fungal spores in the ambient atmosphere were monitored with a Burkard volumetric spore trap on an exposed roof in North London from autumn 1991 until the summer of 1992. Indoor spore measurements were taken in 19 homes in the vicinity through the winter months, both by direct air sampling using a portable Burkard sampler and by dust culture. Trends in the occurrence and concentrations of fungal spores indoors and outdoors were examined. Relationships between the abundance of selected allergenic fungi and features of the houses were analysed including age of dwelling, dampness, cleanliness and presence of pets.Aspergillus andPenicillium were the most frequently occurring spore types in the homes. Overall, high spore incidence was associated with dampness and dust accumulation. The outdoor spore samples revealed generally low concentrations through the winter until March when concentrations of many types includingCladosporium, Epicoccum andAlternaria increased in abundance in response to the warmer weather. Even during the late-spring and early-summer, concentrations of most fungal spores were notably below those reported for rural sites.     

Long-term use of high-efficiency vacuum cleaners and residential airborne fungal-spore exposure

Exposure to fungal allergens is an important contributor to allergic respiratory disease, but information on the efficacy of residential fungal allergen-avoidance in allergic-disease management is lacking. Using vacuum cleaners with high-efficiency exhaust filtration is one method recommended for reducing residential allergen exposure levels, but their use to reduce fungal-spore exposure levels has not been evaluated. To evaluate the effectiveness of high-efficiency vacuuming to control airborne fungal-spore levels, fungal bioaerosols were repeatedly assessed over the course of 10 months in homes randomly assigned to groups using either conventionally filtered (control) or high-efficiency-filtered vacuum cleaners for routine vacuum cleaning. Air samples were analyzed for three fungal-spore categories representing taxa with predominantly outdoor sources and one representing taxa that commonly have indoor sources. In a two-way analysis of variance, sampling period had a significant effect on mean levels of all fungal-spore categories. Vacuum cleaner type had a marginally significant effect on the indoor spore category, with one high-efficiency vacuum group mean (of three) significantly lower than one control mean. No effect was observed of vacuum cleaner type on outdoor spore categories. Including home-environment variables in analysis of covariance models strengthened the effect of the vacuum-type treatment on the indoor spore category, with no effect on the three outdoor spore categories. Decreased indoor spore levels vs. controls were only observed in high-efficiency vacuum groups during the last sampling period, at the end of the heating season. The results suggest that using a vacuum with high-efficiency filtered exhaust could have some modest effectiveness in controlling airborne fungal-spore exposure in homes when infiltration of outdoor air is very limited.     

Long-term use of high-efficiency vacuum cleaners and residential airborne fungal-spore exposure

Exposure to fungal allergens is an important contributor to allergic respiratory disease, but information on the efficacy of residential fungal allergen-avoidance in allergic-disease management is lacking. Using vacuum cleaners with high-efficiency exhaust filtration is one method recommended for reducing residential allergen exposure levels, but their use to reduce fungal-spore exposure levels has not been evaluated. To evaluate the effectiveness of high-efficiency vacuuming to control airborne fungal-spore levels, fungal bioaerosols were repeatedly assessed over the course of 10 months in homes randomly assigned to groups using either conventionally filtered (control) or high-efficiency-filtered vacuum cleaners for routine vacuum cleaning. Air samples were analyzed for three fungal-spore categories representing taxa with predominantly outdoor sources and one representing taxa that commonly have indoor sources. In a two-way analysis of variance, sampling period had a significant effect on mean levels of all fungal-spore categories. Vacuum cleaner type had a marginally significant effect on the indoor spore category, with one high-efficiency vacuum group mean (of three) significantly lower than one control mean. No effect was observed of vacuum cleaner type on outdoor spore categories. Including home-environment variables in analysis of covariance models strengthened the effect of the vacuum-type treatment on the indoor spore category, with no effect on the three outdoor spore categories. Decreased indoor spore levels vs. controls were only observed in high-efficiency vacuum groups during the last sampling period, at the end of the heating season. The results suggest that using a vacuum with high-efficiency filtered exhaust could have some modest effectiveness in controlling airborne fungal-spore exposure in homes when infiltration of outdoor air is very limited.     

Glomus intraradices dominates arbuscular mycorrhizal communities in a heavy textured agricultural soil

Arbuscular mycorrhizal fungal (AMF) spore communities were surveyed in a long-term field fertilization experiment in Switzerland, where different amounts of phosphorus (P) were applied to soil. Plots receiving no P as well as plots systematically fertilized in excess to plant needs for 31 years were used to test the hypothesis that application of P fertilizer changes the composition and diversity of AMF communities. AMF spores were isolated from the field soil, identified, and counted so as to quantify the effect of P fertilization on AMF spore density, composition, and diversity. Trap cultures were established from field soil with four host plants (sunflower, leek, maize, and Crotalaria grahamiana), and the spore communities were then analyzed in substrate samples from the pots. Altogether, nine AMF species were detected in the soil. No evidence has been acquired for effect of P fertilization on spore density, composition, and diversity of AMF in both the field soil and in trap cultures. On the other hand, we observed strong effect of crop plant species on spore densities in the soil, the values being lowest under rapeseed and highest under Phacelia tanacetifolia covercrop. The identity of plant species in trap pots also significantly affected composition and diversity of associated AMF communities, probably due to preferential establishment of symbiosis between certain plant and AMF species. AMF spore communities under mycorrhizal host plants (wheat and Phacelia in the fields and four host plant species in trap pots) were dominated by a single AMF species, Glomus intraradices. This resulted in exceptionally low AMF spore diversity that seems to be linked to high clay content of the soil.Electronic supplementary material Supplementary material is available for this article at and accessible for authorised users.     

Determining Fungi rRNA Copy Number by PCR

The goal of this project is to improve the quantification of indoor fungal pollutants via the specific application of quantitative PCR (qPCR). Improvement will be made in the controls used in current qPCR applications. This work focuses on the use of two separate controls within a standard qPCR reaction. The first control developed was the internal standard control gene, benA. This gene encodes for β-tubulin and was selected based on its single-copy nature. The second control developed was the standard control plasmid, which contained a fragment of the ribosomal RNA (rRNA) gene and produced a specific PCR product. The results confirm the multicopy nature of the rRNA region in several filamentous fungi and show that we can quantify fungi of unknown genome size over a range of spore extractions by inclusion of these two standard controls. Advances in qPCR have led to extremely sensitive and quantitative methods for single-copy genes; however, it has not been well established that the rRNA can be used to quantitate fungal contamination. We report on the use of qPCR, combined with two controls, to identify and quantify indoor fungal contaminants with a greater degree of confidence than has been achieved previously. Advances in indoor environmental health have demonstrated that contamination of the built environment by the filamentous fungi has adverse impacts on the health of building occupants. This study meets the need for more accurate and reliable methods for fungal identification and quantitation in the indoor environment.     

Sources of Variability in the Measurement of Fungal Spore Yields

Variability in the production of fungal spores and in the measurement of spore yields was investigated in four species of fungi: Colletotrichum gloeosporioides, Colletotrichum coccodes, Colletotrichum phomoides, and Acremonium strictum. When the fungi were grown on solid medium in microplates and spore yields were measured by counting the subsamples with a hemacytometer, the variability among hemacytometer squares was always the largest source of variation, accounting for 51 to 91% of the total variation. Variability among replicate cultures and results of repeat experiments were generally also significant. The effect of square-to-square variability on the precision of spore yield measurement was minimized by counting a moderate number (ca. 30) of squares per culture. Culture-to-culture variability limited the practical precision of spore production measurements to a 95% confidence interval of approximately the mean ± 25%. We provide guidelines for determining the number of replicate cultures required to attain this or other degrees of precision. Particle counter-derived spore counts and counts based on spore weights were much less variable than were hemacytometer counts, but they did not improve spore production estimates very much because of culture-to-culture variability. Results obtained by both of these methods differed from those obtained with a hemacytometer; particle counter measurements required a correction for spore pairs, while the relationship between spore weights and spore counts changed as the cultures aged.     

Fungal and Bacterial Communities in Indoor Dust Follow Different Environmental Determinants

People spend most of their time inside buildings and the indoor microbiome is a major part of our everyday environment. It affects humans’ wellbeing and therefore its composition is important for use in inferring human health impacts. It is still not well understood how environmental conditions affect indoor microbial communities. Existing studies have mostly focussed on the local (e.g., building units) or continental scale and rarely on the regional scale, e.g. a specific metropolitan area. Therefore, we wanted to identify key environmental determinants for the house dust microbiome from an existing collection of spatially (area of Munich, Germany) and temporally (301 days) distributed samples and to determine changes in the community as a function of time. To that end, dust samples that had been collected once from the living room floors of 286 individual households, were profiled for fungal and bacterial community variation and diversity using microbial fingerprinting techniques. The profiles were tested for their association with occupant behaviour, building characteristics, outdoor pollution, vegetation, and urbanization. Our results showed that more environmental and particularly outdoor factors (vegetation, urbanization, airborne particulate matter) affected the community composition of indoor fungi than of bacteria. The passage of time affected fungi and, surprisingly, also strongly affected bacteria. We inferred that fungal communities in indoor dust changed semi-annually, whereas bacterial communities paralleled outdoor plant phenological periods. These differences in temporal dynamics cannot be fully explained and should be further investigated in future studies on indoor microbiomes.     

First volumetric records of airborne Cladosporium and Alternaria spores in the atmosphere of Al Khor (northern Qatar): a preliminary survey

Aerobiologia - Daily monitoring of airborne fungal spores was carried out for the first time in Al Khor city, Qatar, using a Hirst type 7-day recording volumetric spore trap, from May 2017 to May...     

Characterizing and handling different kinds of AM fungal spores in the rhizosphere

Spores are important propagules as well as the most reliable species-distinguishing traits of arbuscular mycorrhizal (AM) fungi. During surveys of AM fungal communities, spore enumeration and spore identification are frequently conducted, but generally little attention is given to the age and viability of the spores. In this study, AM fungal spores in the rhizosphere were characterized as live or dead by vital staining and by performing a germination assay. A considerable proportion of the spores in the rhizosphere were dead despite their intact appearance. Furthermore, morphological and molecular analyses of spores to determine species identity revealed that both viable spores and dead spores with contents were identified. The accurate identification of spores at different developmental stages on the basis of morphology requires considerable experience. Our findings suggest that surveys of AM fungal communities based on spore enumeration and morphological and molecular identification are likely to be inaccurate, primarily because of the large proportion of dead spores in the rhizosphere. A viability check is recommended prior to spore molecular identification, and the use of trap cultures would give more reliable morphological identification results. We show that the abundance and activity of AM fungi in the rhizosphere can be determined by calculating the density of viable spores and the density of spores that could germinate. The adoption of these methods should provide a more reliable basis for further AM fungal community analysis.     

Development of a fungal spore aerosol generator: test with Cladosporium cladosporioides and Penicillium citrinum

As the first step to develop efficient means to control fungal spore bioaerosols, we designed, manufactured, and evaluated a fungal spore aerosol generator. We studied the physical and biological properties of the fungal spore bioaerosols on two common fungal species. The results demonstrated that the fungal spore bioaerosol generator effectively produces fungal spore bioaerosols.