Dispersal of fungal spores from three types of air handling system duct material

Exposure to airborne microorganisms in indoor environments may result in infectious disease or elicit an allergic or irritant response. Air handling system components contaminated by fungi have been implicated in the dispersal of spores into the indoor environment, thereby serving as a route of exposure to occupants. This study was conducted to provide quantitative data on the dispersal of spores from fungal colonies growing on three types of duct material. Galvanized metal, rigid fibrous glass ductboard, and fiberglass duct liner were soiled and contaminated with a known concentration of Penicillium chrysogenum spores. The duct materials were incubated in humidity chambers to provide a matrix of growing, sporulating fungal colonies at a contamination level of 109 colony forming units (CFU) per duct section, consistent for all materials. For each experiment a contaminated duct section was inserted into the air handling system of an experimental room, and the air handling system was operated for three 5-minute cycles with an air flow of 4.2 m3 min–1. The duct air velocity was approximately 2.8 m sec–1. The airborne concentration of culturable P. chrysogenum spores (CFU m–3), total P. chrysogenum spores (spores m–3), and total P. chrysogenum-sized particles (particles m–3) were measured in the room using Andersen single-stage impactor samplers, Burkard slide impactor samplers, and an aerodynamic particle sizer, respectively. The highest airborne concentrations (104 CFU m–3; 105 spores m–3; 104 particles m–3) were measured during the first operating cycle of the air handling system for all duct materials with decreasing airborne concentrations measured during the second and third cycles. There was no significant difference in spore dispersal from the three contaminated duct materials. These data demonstrate the potential exposure for building occupants to high concentrations of spores dispersed from fungal colonies on air handling system duct materials during normal operation of the system.     

Fungal fragments as indoor air biocontaminants

The aerosolization process of fungal propagules of three species (Aspergillus versicolor, Penicillium melinii, and Cladosporium cladosporioides) was studied by using a newly designed and constructed aerosolization chamber. We discovered that fungal fragments are aerosolized simultaneously with spores from contaminated agar and ceiling tile surfaces. Concentration measurements with an optical particle counter showed that the fragments are released in higher numbers (up to 320 times) than the spores. The release of fungal propagules varied depending on the fungal species, the air velocity above the contaminated surface, and the texture and vibration of the contaminated material. In contrast to spores, the release of fragments from smooth surfaces was not affected by air velocity, indicating a different release mechanism. Correlation analysis showed that the number of released fragments cannot be predicted on the basis of the number of spores. Enzyme-linked immunosorbent assays with monoclonal antibodies produced against Aspergillus and Penicillium fungal species showed that fragments and spores share common antigens, which not only confirmed the fungal origin of the fragments but also established their potential biological relevance. The considerable immunological reactivity, the high number, and the small particle size of the fungal fragments may contribute to human health effects that have been detected in buildings with mold problems but had no scientific explanation until now. This study suggests that future fungal spore investigations in buildings with mold problems should include the quantitation of fungal fragments.     

医院病房环境真菌监测分析

目的 调查医院各病区环境中真菌含量及分布特点.方法 运用分离培养及DNA测序方法对医院不同病区、不同环境中真菌进行监测分析.结果 医院不同病区真菌含量不同,呼吸科、血液科、小儿科空气中真菌含量较高,分别为400、225和200 CFU/m3,其中以烟曲霉菌( 325 CFU/m3)、黄曲霉菌( 275 CFU/m3)、枝孢霉菌( 125 CFU/m3)、根霉( 125 CFU/m3)为主;老年病科、肿瘤科和血液科空调出气口真菌含量较高,分别为0.559、0.500和0.323 CFU/cm2,以链格孢霉(0.441 CFU/cm2)、根霉(0.412 CFU/cm2)、烟曲霉菌(0.294 CFU/cm2)为主;不同环境中真菌含量不同,其中以空气和空调出气口真菌含量最高,分别为130 CFU/m3、0.173 CFU/cm2.结论 真菌广泛存在于医院环境中,且不同病区、不同环境真菌污染程度不同,因而我们必须制订健全的消毒管理制度,预防医院真菌感染.     

Characterization of an airborne microbial community: A case study in the archive of the University of Coimbra,Portugal

Understanding the structure of indoor airborne microbial communities could be useful in optimizing conservation and disinfection procedures in archive repositories, preventing the biodeterioration of stored collections. In this study we characterized the microbial air community inside the Archive of the University of Coimbra, by identifying different fungal and bacterial organisms retrieved from air samples. The microbial contamination was determined using conventional culture methods, and the isolates were typified using morphological techniques. Results indicated a low microbial air contamination (107 ± 12 CFU/m³), particularly regarding fungal propagules (6 ± 1 CFU/m³). Fungal isolates were identified using ITS-DNA sequencing. Among fungal isolates, Penicillium was the most frequent genus, and Penicillium griseofulvum was the predominant species. Simpson diversity index (1-D) was applied to phenotypic and genotypic results. Total phenotypic diversity varied from 0.4 to 0.8 and regarding fungal species, the diversity was higher than 0.5. These results were compared with previous analyses of the Archive's air, suggesting that short-term changes in atmospheric conditions may influence the indoor air microbial community structure.     

Abundance of airborne Penicillium CFU in relation to urbanization in Mexico City.

Air was sampled simultaneously at three localities in Mexico City differing in urbanization index and air pollution level on 22 days during a period covering both dry and rainy seasons. An Andersen two-stage microbial sampler was used for 15 min at 28 liters min-1 to isolate culturable fungi on malt extract agar. After exposure, plates were incubated at 25 degrees C for 48 to 72 h before colonies were counted and identified to give concentrations of total fungal spores and of Penicillium spp., expressed as CFU per cubic meter of air. Total fungi numbered 91 to 602 CFU m-3 in Tlalpan Borough (southern area), 40 to 264 CFU m-3 in Cuauhtémoc Borough (downtown), and 26 to 495 CFU m-3 in Gustavo A. Madero Borough (northern area). Although Penicillium spp. were the second most frequently isolated fungal genus, concentrations were small, with a maximum of only 133 CFU m-3. Twice as many colonies were isolated in the southern area, with an urbanization index of 0.25 (arithmetic mean, 41 CFU m-3), as at other sampling stations with greater urbanization indices (arithmetic means, 19 and 20 CFU m-3). In the downtown area, with an urbanization index of 1.0, Penicillium spp. were more numerous than any other genus and formed 25% of the total fungal count compared with 14 and 17% in the other areas. Concentrations of airborne Penicillium spp. did not differ significantly between rainy and dry seasons.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fungal Fragments as Indoor Air Biocontaminants

The aerosolization process of fungal propagules of three species (Aspergillus versicolor, Penicillium melinii, and Cladosporium cladosporioides) was studied by using a newly designed and constructed aerosolization chamber. We discovered that fungal fragments are aerosolized simultaneously with spores from contaminated agar and ceiling tile surfaces. Concentration measurements with an optical particle counter showed that the fragments are released in higher numbers (up to 320 times) than the spores. The release of fungal propagules varied depending on the fungal species, the air velocity above the contaminated surface, and the texture and vibration of the contaminated material. In contrast to spores, the release of fragments from smooth surfaces was not affected by air velocity, indicating a different release mechanism. Correlation analysis showed that the number of released fragments cannot be predicted on the basis of the number of spores. Enzyme-linked immunosorbent assays with monoclonal antibodies produced against Aspergillus and Penicillium fungal species showed that fragments and spores share common antigens, which not only confirmed the fungal origin of the fragments but also established their potential biological relevance. The considerable immunological reactivity, the high number, and the small particle size of the fungal fragments may contribute to human health effects that have been detected in buildings with mold problems but had no scientific explanation until now. This study suggests that future fungal spore investigations in buildings with mold problems should include the quantitation of fungal fragments.     

Comparison of methods for estimating the biomass of three food-borne fungi with different growth patterns.

To evaluate the effectiveness of steps taken to reduce the growth of molds in food and feed, methods that can accurately quantify the degree of fungal contamination of solid substrates are needed. In this study, the ergosterol assay has been evaluated by comparing the results of this assay with spore counts and hyphal length measurements made with a microscope and with CFU counts. Three fungi with different growth patterns during cultivation on a synthetic agar substrate were used in these experiments. For the nonsporulating Fusarium culmorum, there was good agreement between changes in hyphal length, CFU, and ergosterol content. Penicillium rugulosum and Rhizopus stolonifer produced many spores, and the production of spores coincided with large increases in CFU but not with increases in hyphal length or ergosterol content. Spores constituted between 3 and 5% of the total fungal mass. Changes in ergosterol level were closely related to changes in hyphal length. It was concluded that ergosterol level is a suitable marker for use in quantitatively monitoring fungal growth in solid substrates.     

Growth of moulds inoculated into commercial mineral water

The growth of mould spores of Penicillium sp. and Cladosporium sp. inoculated in a commercial mineral water product was studied. The strains had been isolated as fungal foreign bodies in commercial mineral waters. In product A, which was not originally sterilized and was contaminated with psychrophilic bacteria, the inoculated mould spores of the strains did not grow; no increases in viable colony counts or beta-glucans concentration in the samples were observed during storage. In a sterilized product A, inoculated spores of the strains grew into visible foreign bodies. The viable colony counts and the beta-glucans concentration in the samples increased during storage. These results showed that in a sterilized mineral water product, mould spores could grow into visible foreign bodies.     

Mold challenge study in bottled natural mineral waters and spring waters

Microbiological challenge study was carried out to verify the microbial stability of bottled waters against four different mold species isolated from bottled water (Fusarium sp.; Cladosporium sp.; Penicillium chrysogenum and Aspergillus fumigatus) and to follow the growth of the molds in bottled water. Twelve types of bottled water with different mineralization and CO2 level in PET and glass packages were collected from 4 European countries. Three different inoculation levels of spore suspensions were used to contaminate bottled water samples. The surviving colony forming unit (CFU) numbers and visual growth were monitored during the investigation period (26 weeks). The results of surviving CFU showed that the fungal growth is mostly determined by the carbonation level and the type of the mold strain. Neither the inoculation level nor the mineral content had any significant effect on the survival of the different mold strains. Results showed decreased CFU numbers in carbonated waters, while slow decreasing, stagnation or even some growth in still waters. A. fumigatus was the most resistant test species. None of the other tested mold strains survived the first 12-week test period in carbonated water. Visual growth was not detected in carbonated water samples, in contrast to all of the non-carbonated samples.     

Biocontrol of mold growth in high-moisture wheat stored under airtight conditions by Pichia anomala, Pichia guilliermondii, and Saccharomyces cerevisiae.

Pichia anomala inhibits the growth of Penicillium roqueforti and Aspergillus candidus on agar. In this investigation, antagonistic activity on agar against 17 mold species was determined. The abilities of Pichia anomala, Pichia guilliermondii, and Saccharomyces cerevisiae to inhibit the growth of the mold Penicillium roqueforti in nonsterile high-moisture wheat were compared by adding 10(3) Penicillium roqueforti spores and different amounts of yeast cells per gram of wheat. Inoculated grain was packed in glass tubes, incubated at 25 degrees C with a restricted air supply, and the numbers of yeast and mold CFU were determined on selective media after 7 and 14 days. Pichia anomala reduced growth on agar plates for all of the mold species tested in a dose-dependent manner. Aspergillus fumigatus and Eurotium amstelodami were the most sensitive, while Penicillium italicum and Penicillium digitatum were the most resistant. Pichia anomala had the strongest antagonistic activity in wheat, with 10(5) and 10(6) CFU/g completely inhibiting the growth of Penicillium roqueforti. Inhibition was least pronounced at the optimum temperature (21 degrees C) and water activity (0.95) for the growth of Penicillium roqueforti. Pichia guilliermondii slightly reduced the growth of Penicillium roqueforti in wheat inoculated with 10(5) and 10(6) yeast CFU/g. S. cerevisiae inhibited mold growth only weakly at the highest inoculum level. Pichia anomala grew from 10(3) to 10(7) CFU/g of wheat in 1 week. To reach the same level, Pichia guilliermondii had to be inoculated at 10(4) CFU while S. cerevisiae required an inoculum of 10(5) CFU to reach 10(7) CFU/g of wheat.     

Differences in the microflora of scarified and unscarified seeds ofKarwinskia humboldtiana (Rhamnaceae)

Seeds ofKarwinskia humboldtiana obtained from a 1997 collection in the locality of Villa de García Nuevo (León, Mexico) were contaminated with spores of filamentous fungi, bacteria and yeasts. The concentration of microorganisms in unscarified seeds ranged from 3.0×10³ to 7.5×10³ CFU/g. Predominant were bacterial isolates of the generaAeromonas sp.,Bacillus, andPseudomonas; from filamentous fungi were identifiedAlternaria, Aspergillus niger, Cladosporium sp.,Fusarium sp.,Mucor sp.,Penicillium commune, Trichothecium sp.; from yeastsRhodotorula sp. andSaccharomyces cerevisiae. Seed scarification significantly reduced the microbial contamination. Of the original fungal isolates, only two were identified on scarified seeds,viz. Cladosporium sp. andSaccharomyces cerevisiae; although a relatively high incidence of a unidentifiable ofPenicillium sp. was found, the bacterial spectrum was not altered. Treatment of scarified seeds with Vitavax 200 WP and Pomarsol Forte 80 WP (3 mg/g seeds) augmented germination by 10–19% compared to treated unscarified seeds, and by 16–31% compared to untreated unscarified seeds.     

Aerometric study of viable fungus spores in an animal care facility.

Studies of airborn fungi were undertaken to evaluate exposure risks for laboratory animals and human handlers which might lead to allergic or invasive disease. Although sporadically high fungus levels were encountered, counts of viable fungus particles were in general low. Recoveries on malt extract agar significantly exceeded those on Sabouraud dextrose agar. The taxa most frequently and abundantly recovered were Penicillium species. Data analyses suggest that 'clean' bedding material may be the principal source of these spores, that cleaning temporarily increases spore levels, and that outdoor airborne fungi contributed little to the indoor air spora identified. Aspergillus fumigatus was infrequently encounted in our samples, and dermatophytes were not recovered.     

FsFKS1, the 1,3-beta-glucan synthase from the caspofungin-resistant fungus Fusarium solani

The cell wall, a mesh of carbohydrates and proteins, shapes and protects the fungal cell. The enzyme responsible for the synthesis of one of the main components of the fungal wall, 1,3-beta-glucan synthase, is targeted by the antifungal caspofungin acetate (CFA). Clinical isolates of Candida albicans and Aspergillus fumigatus are much more sensitive to CFA than clinical isolates of Fusarium species. To better understand CFA resistance in Fusarium species, we cloned and sequenced FsFKS1, which encodes the Fusarium solani f. sp. pisi beta(1,3)-D-glucan synthase, used RNA interference to reduce its expression and complemented deletion of the essential fks gene of the CFA-sensitive fungus A. fumigatus with FsFKS1. Reduction of the FsFKS1 message in F. solani f. sp. pisi reduced spore viability and caused lysis of spores and hyphae, consistent with cell wall defects. Compensating for the loss of A. fumigatus fks1 with FsFKS1 caused only a modest increase in the tolerance of A. fumigatus for CFA. Our results suggest that FsFKS1 is required for the proper construction of F. solani cell walls and that the resistance of F. solani to CFA is at best only partially due to resistance of the FsFKS1 enzyme to this antifungal agent.     

Fungal Air Spora at Ibadan, Nigeria

The fungal air spora at Ibadan, Nigeria, was investigated by using Casella Slit Samplers. Three sites, incorporating three locations at each site, were selected for the exposure of replicate plates during sampling. To provide data on a wide range of saprophytic and pathogenic fungal spores, isolations were made on Sabouraud dextrose agar and malt agar plates incubated at 26 and 37 C. Altogether over 60,000 fungal colonies were isolated and counted during the 12-month sampling period. The prevalent fungal genera recorded were: Cladosporum, Curvularia, Fusarium, Aspergillus, Penicillium, Pithomyces, Aureobasidium, Geotrichum, Phoma, Nigrospora, Epicoccum, and Neurospora. The wet and dry seasons (indicated by the temperature, relative humidity, and rainfall data) caused seasonal periodicity in colony numbers. The influence of culture media on the isolated colonies was not significant when the total number of isolated colonies were considered on a monthly basis, but in reviewing a few of the fungal genera there were marked differences between the two media, especially with Pithomyces. Attempts were made to identify some of the isolated colonies by species, e.g., Aspergillus carneus, Aspergillus flavus, Aspergillus fumigatus, Curvularia geniculata, Fusarium oxysporum, Penicillium herquei, Pithomyces chartaum, Rhizopus arrhizus, and Syncephalastrum racemosum. Such identifications provide a basis for further studies on the role of these fungal species in the frontier problem of contamination and biodegradation of drugs and pharmaceuticals, allergies and other problems in the local environment.     

Allergic potential of someAspergilli on saw mill workers in Lucknow,India

Fifty fungal types were isolated from the indoor atmosphere of saw mills by exposing Petri plates containing Czapek-dox Agar, Potato-dextrose Agar and Sabouraud Agar media for 5 min. The fungal flora of the outdoor surroundings was also studied for comparison. Species ofAspergilli dominated in the saw mills, being represented by 16 species including one ascosporic form. Other fungi were species ofCladosporium, Alternaria, Curvularia, Penicillium, Fusarium, etc. Variations in the fungal population in different months were also observed. Fungal spores recovered using the Rotorod Sampler wereAlternaria, Curvalaria lunata, Curvularia tetramera, Cladosporium, Dreschslera sp.,Epicoccum sp.,Pithomyes sp.,Nigrospora, Stemphylium sp. andTorula sp. Mycelial fragments and unidentifiable spores were also seen in abundance. Varying allergic responses of patients were also recorded by testing intradermally, the antigens of nineAspergilli, vizAspergillus flavus, A. fumigatus, A. japonicus, A. melleus, A. nidulans, A. niger, A. niveus, A. tammarii and A. terreus.     

Allergic potential of someAspergilli on saw mill workers in Lucknow,India

Fifty fungal types were isolated from the indoor atmosphere of saw mills by exposing Petri plates containing Czapek-dox Agar, Potato-dextrose Agar and Sabouraud Agar media for 5 min. The fungal flora of the outdoor surroundings was also studied for comparison. Species ofAspergilli dominated in the saw mills, being represented by 16 species including one ascosporic form. Other fungi were species ofCladosporium, Alternaria, Curvularia, Penicillium, Fusarium, etc. Variations in the fungal population in different months were also observed. Fungal spores recovered using the Rotorod Sampler wereAlternaria, Curvalaria lunata, Curvularia tetramera, Cladosporium, Dreschslera sp.,Epicoccum sp.,Pithomyes sp.,Nigrospora, Stemphylium sp. andTorula sp. Mycelial fragments and unidentifiable spores were also seen in abundance. Varying allergic responses of patients were also recorded by testing intradermally, the antigens of nineAspergilli, vizAspergillus flavus, A. fumigatus, A. japonicus, A. melleus, A. nidulans, A. niger, A. niveus, A. tammarii and A. terreus.     

An imidazole derivative (Econazole) as an antifungal agent in cell culture systems

Econazole, an imidazole derivative, was tested as an antifungal agent in different cell culture systems. In comparison with Fungizone, Econazole has the following advantageous properties: higher stability, higher solubility, better antifungal activity against contaminants of cell cultures and a wider range between minimal inhibitory to cytotoxic concentration with Aspergillus fumigatus, Candida albicans and Penicillium sp., activity against gram-positive bacteria and lower price. Econazole exerts no antiviral effect and can therefore be used for virus isolation from heavily contaminated material. The antagonistic effect of serum on the antifungal effect of Econazole and Fungizone was comparable as was the inhibitory effect of both antimycotics on Mycoplasma growth. In view of the above mentioned properties Econazole lactic acid can be recommended as an antifungal agent for cell culture systems at a concentration of 1 microgram per ml.     

Prevalence and airborne spore levels of Stachybotrys spp. in 200 houses with water incursions in Houston, Texas

Two hundred homes with a history of water incursion were sampled for fungi to determine the prevalence and airborne spore levels of Stachybotrys spp. Sampling methods included room air, surface, and wall cavity air sampling. Stachybotrys spp. were detected with at least one of the methods in 58.5% of the houses tested, but only 9.6% of the room air samples contained Stachybotrys spores. Aerosolization of Stachybotrys spores was correlated with both wall cavity and surface contamination. However, after adjustment for the surface effect, Stachybotrys spores detected in wall cavities were not a significant factor contributing to spores detected in room air samples. We conclude that Stachybotrys spp. are commonly found on water-damaged building materials. In addition, the observations made in this study suggest that the impact on the living space air is low if the fungal spores are contained within a wall cavity.     

FR207944, an antifungal antibiotic from Chaetomium sp. no. 217 I. Taxonomy, fermentation, and biological properties

An antifungal antibiotic, FR207944, was isolated from the culture broth of a fungal strain Chaetomium sp. no. 217. FR207944 is a triterpene glucoside with antifungal activity against Aspergillus fumigatus and Candida albicans. Specifically, FR207944 exhibits in vitro and in vivo antifungal activity against A. fumigatus. The effects of FR207944 on the morphology of A. fumigatus were shown to be similar to those of FR901379, a known 1,3-beta-glucan synthase inhibitor. The MECs of FR207944 against A. fumigatus FP1305 and C. albicans FP633 in micro-broth dilution test were 0.039 and 1.6 mug/ml respectively. FR207944 showed good potency by subcutaneous injection and oral administration against A. fumigatus in a murine systemic infection model, with ED(50)s of 5.7 and 17 mg/kg respectively.     

Monitoring airborne fungal spores in an experimental indoor environment to evaluate sampling methods and the effects of human activity on air sampling.

Aerobiological monitoring was conducted in an experimental room to aid in the development of standardized sampling protocols for airborne microorganisms in the indoor environment. The objectives of this research were to evaluate the relative efficiencies of selected sampling methods for the retrieval of airborne fungal spores and to determine the effect of human activity on air sampling. Dry aerosols containing known concentrations of Penicillium chrysogenum spores were generated, and air samples were taken by using Andersen six-stage, Surface Air System, Burkard, and depositional samplers. The Andersen and Burkard samplers retrieved the highest numbers of spores compared with the measurement standard, an aerodynamic particle sizer located inside the room. Data from paired samplers demonstrated that the Andersen sampler had the highest levels of sensitivity and repeatability. With a carpet as the source of P. chrysogenum spores, the effects of human activity (walking or vacuuming near the sampling site) on air sampling were also examined. Air samples were taken under undisturbed conditions and after human activity in the room. Human activity resulted in retrieval of significantly higher concentrations of airborne spores. Surface sampling of the carpet revealed moderate to heavy contamination despite relatively low airborne counts. Therefore, in certain situations, air sampling without concomitant surface sampling may not adequately reflect the level of microbial contamination in indoor environments.