Journal of Medicaland VeterinaryMycology (1992), 30, Supplement 1,279-285
Ecology of fungi in human dwellings R. C. SUMMERBELL 1,2, F. STAIB 3, R. DALES 4,5, N. N O L A R D 6, J. KANE z,7, H. Z W A N E N B U R G 4, R. B U R N E T T 4, S. K R A J D E N 2'7, D. FUNG 8 AND
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D. LEONG 8
1Mycology, Ontario Ministry of Health, Box 9000, Terminal A, Toronto, Ontario, and 2Department of Microbiology, University of Toronto, Toronto, Canada; 3Robert Koch Institut des Bundesgesundheitsamtes, Berlin, Germany; 4Health Protection Branch, Health and Welfare Canada, Ottawa, and 5University of Ottawa, Ottawa, Canada; 6Institut d'Hygidne et d'EpidOmiologie, Ministdre de la Santo Publique et de l'environnement, Brussels, Belgium; 7St. Joseph's Health Centre, Toronto, and SOccupational Health, Ontario Ministry of Labour, Toronto, Canada Human dwellings are seldom sources of invasive mycotic disease in immunocompetent persons but may harbour molds and yeasts capable of causing opportunistic infection and allergenically mediated disease. In addition, household molds have recently been associated epidemiologically with non-specific respiratory complaints of uncertain aetiology. Investigators worldwide are now exploring the connections between domestic fungi and the symptoms of non-invasive diseases such as hypersensitivity pneumonitis, and also are conducting fundamental studies on the ecology of mycotic agents of disease and allergic distress. Presented below are four topics representative of our current state of knowledge on the domestic ecology of fungi associated with morbidity and mortality. Canadian air quality health survey: influence of home dampness and moulds on respiratory health
Canadian homes, because of the cold climate, tend to be well insulated and may consequently have reduced fresh air exchange [9]. Since North Americans spend little time outside, indoor air quality is understandably an important issue. Dampness, with resulting mould growth, has been associated with non-specific respiratory symptoms in several countries. In 1988 a large questionnaire-based study was conducted to investigate this problem in Canadian homes. Six Canadian regions spanning the east to west coast were selected for study. These were: The Maritimes, Quebec, Muskoka Ontario, Southwestern Ontario, Saskatchewan and British Columbia. Within each region five agricultural service towns were selected, none of which had local industrial sources of outdoor air pollution. Children who attended kindergarten to grade three, between March and April 1988, were eligible to receive questionnaires to be completed by the parent or guardian most familiar with the child's health. The questionnaire questions used in the present study were taken or modified from the American Thoracic Society - Division of Lung Disease Respiratory Symptom Questionnaire, used by the Harvard School of Public Health in the six city 279
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study, and the Basic Standard Environmental Inventory Questionnaire developed by Lebowitz et al. [4, 5, 10]. Home dampness/mold was defined as the reported presence of wet or damp spots on inside surfaces, leaking or flooding in the basement, and mould or mildew growing inside the home. Lower respiratory symptoms were defined as the report of any of; cough, phlegm, wheeze, or wheeze with dyspnea in adults. In children, the definition was similar except that persistent phlegm was not included. A total of 17 962 parents or guardians received a questionnaire and 14 948 (83%) were returned. A total of 12 569 children between the ages of 5 and 8 years, and 14 799 adults, at least 21 years of age, were available for analysis. Reported prevalence of home dampness/mould was 38%. Symptom prevalence among children was 19.5% versus 13.2%, among those with and without reported home dampness/mould. Corresponding values for adults were: 38% versus 27% among current smokers, 21% versus 14% for ex-smokers, and 19% versus 11% for individuals who had never smoked. The corresponding adjusted odds ratio for children was 1.50 (95% CI 1.35, 1.67), and for adults combining smoking categories was 1.62 (95% CI 1.48, 1.78). We found that home dampness and mould were associated with increased respiratory symptoms among both adults and children. The findings persisted despite adjustment for other influencing variables and were consistent with studies from other countries [1, 2, 6]. The reported prevalence of home dampness or moulds in Canadian homes, approximately 38%, indicates that it is an important public health issue. Further studies are required to elucidate the symptom pathogenesis.
Fungi causing allergy: their ecology and significance within dwellings Since the first world oil crisis in the 1970s, Belgium has seen a continuing increase in complaints of an allergic nature correlated with habitat. Indeed, in order to reduce energy costs due to the heating of homes, under pressure from the public authorities, people have begun to renovate their houses with the aim of best insulating every part, from the cellar to the attic. This has been done so relentlessly that, in Belgium, the public authorities have created grants 'for renovation' which are accorded only in relation to the degree of energy saving attained by the transformations. In addition, the effectiveness of the insulation has since become one of the major selling points in the choice of a new house. However, excessive insulation has the effect of exposing allergic individuals to numerous irritants, favouring as it does, through lack of ventilation and renewal of air, the development of numerous moulds. Amongst these are numerous species whose allergenicity had not been tested previously. Our laboratory at the Institute of Hygiene in Brussels has developed a scheme for 'environmental control in the home' which is based on the survey of about 120 homes belonging to allergic patients. This environmental control includes the sampiing itself (air, surface and dust control), the isolation, purification and the placing in the collection of strains destined for immunological testing (more than 2000 strains are either conserved lyophilised or under liquid nitrogen in the IHEM, Brussels collection), the creation of a serum bank containing sera from people living in the environment studied, the standardisation of a mini-method for preparing fungal extracts and, finally, the immunological analysis of sera from allergic patients, from
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subjects exposed to the same environment but not symptomatic and from a pool of test sera. Results indicate that most of the indoor allergenic fungi are not catered for by commercially available extracts and that one must not underestimate the importance of fungi in the home as the cause of type III allergies. The results of these studies have revealed that the sites more often contaminated in the home are: kitchens and bath rooms (Cladosporium cladosporioides, Cladospor-
ium sphaerospermum, Ulocladium botrytis, Chaetomium globosum, Aspergillus fumigatus); wallpaper (C. sphaerospermum, Chaetomium species, Doratomyces species, Fusarium species, Stachybotrys atra, Trichoderma species, Scopulariopsis species); mattresses, carpets (PeniciUium species, Aspergillus versicolor, Aureobasidium pullulans, Aspergillus repens, Wallemia sebi, Chaetomium species); window-frames (A. pullulans, C. sphaerospermum, Ulocladium species); cellars and crawl spaces (A. versicolor, A. fumigatus, Fusarium species); the soil of ornamental plants (A. fumigatus, Aspergillus niger and Aspergillus flavus); insulation material (A. versicolor, A. fumigatus, Fusarium species). Pathogenic fungi in human dwellings There is a difference between dwellings in the zones of temperate and tropical climates. In an area of temperate climate like Germany, the subject of pathogenic fungi in human dwellings has nothing to do with infections of the immunocompetent host, but rather with infections connected to immunosuppressive therapy or defined immunodeficiencies. Of prime interest are airborne invasive infections of such highrisk patients by fungi occupying habitats within dwellings such as private houses or hospitals. The most important agents of mycotic infection in immunodeficient persons are some Aspergillus species, some species of Mucoraceae, and Cryptococcus neoforroans. Together with other micro-organisms, these fungi are normally vigorous decomposers of various types of detritus. The indoor habitats of Aspergillus species and Mucoraceae include the soil of potted indoor plants. Our observations on the high frequency of Aspergillus species in the soil of indoor plants and on their possible epidemiological role in hospitals were confirmed by the thorough investigations of Summerbell et al. [8]. Mucoraceae such as Rhizopus, Rhizomucor, Absidia and Mucor species could also be isolated by us from the soil of potted plants. Additionally, we have found that the growth of polyene-producing streptomycetes in the rhizosphere of a potted plant may influence the presence or absence of particular fungal agents, a result which is of strong ecological and epidemiological interest. Neutropenic patients exposed to soil of potted plants in the hospital may become infected by A. furnigatus, A. niger, A. flavus, Absidia corymbifera and Rhizopus species. Proving the source of such an infection will always be difficult. In fatal cases where identical combinations of two or three fungi (e.g.A. fumigatus, A. flavus and A. corymbifera) have been isolated from autopsy material and from the soil of the plant next to the patient, a probable association has been inferred. Air sampling has been of great help in such studies. Other probable sources of fatal Aspergillus infections of hospitalized neutropenic patients included other patients with aspergillosis in the hospital, food products like nuts, uncooked dry vegetarian food, and spices such as pepper, neglected hydro-
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culture plants, ventilation systems and construction dust. In one diabetic patient, the probable source of rhinocerebral infection by Rhizopus oryzae was 'cat grass' heavily colonized by this fungus in the patient's living room. Our investigations of the 'biological waste container' newly introduced in Germany have shown that in the very first stage of composting during the collection of waste in the household (about 1 week), A. fumigatus and Mucoraceae grow and may become a focus of air contamination and a source of infection for immunocompromised persons. C. neoformans vat. neoformans in nature is specialized to degrade concentrated, relatively bacteria-free bird urine, therefore, habitats of this yeast are not as widespread as those of aspergilli and Mucoraceae in our environment. This may also be the reason why C. neoformans infections do not occur with a frequency that could be expected in view of the number of persons with an immunopathological predisposition for cryptococcosis (e.g. only 3-5% of AIDS patients are positive). In Berlin, approximately 1-6% of bird cages have been found to be positive for C. neoformans var. neoformans and the droppings of feral pigeons in 7% of sheltered places such as church spires. C. neoformans var. gattii was never isolated from bird droppings. In Berlin, C. neoformans is not found outdoors. Since 1983 all strains from the droppings of caged birds examined produced a weak creatinine auxanogram and proved to be serotype A, while those of pigeons which produced intense creatinine auxanograms proved to be of either serotype A or D (serotyping was performed by Dr J. Kwon-Chung). Surprisingly, there have been no reports of nosocomial infections by C. neoformans, although this fungus may be excreted in the urine of AIDS patients in high quantities (due to the symptom-free involvement of the prostate as an ecological niche for C. neoformans). There is a question as to whether the basidiospore of the perfect state of C. neoformans, namely FilobasidieUa neoformans, is the only infective particle of C. neoformans. Our experiments using bird manure filtrate agar with two compatible strains of C. neoformans showed that constituents of bird urine may support the formation of the perfect state with basidiospore development within 48 h. We have made epidemiological--ecological and diagnostic observations on Aspergillus species, Mucoraceae and C. neoformans var. neoformans in indoor air with the aid of the Reuter centrifugal air sampler in combination with Staib agar + penicillin + streptomycin as a differential medium (syn. Guizotia abyssinica creatinine agar, bird seed agar). In volaries of caged birds in the Berlin zoo, approximately 100 colony forming units (c.f.u.) of Aspergillus species, approximately 40 c.f.u, of Mucoraceae and five c.f.u, of C. neoformans could be isolated from 40 1 of aspirated air. C. neoformans could only be detected when the growth of aspergilli and Mucoraceae was inhibited by addition of biphenyl to Staib agar. Similar proportions of the total c.f.u, counts were found to represent these three different groups of fungi at a number of similar sites. This result shows that a fungus of special epidemiological interest like C. neoformans may be accompanied in air samples by a characteristic assemblage of micro-organisms, all possibly growing within the same habitat and reflecting the stage of decomposition of material in the focus of origin. From the standpoint of pathogenesis, in the case of a person in the primary stage of AIDS inhaling this air, only C. neoformans will start an airborne infection but not the propagules of aspergilli or Mucoraceae. These fungi only cause confusion when the bronchial lavage of persons with AIDS is cultured. In addition, these
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moulds can overgrow the rare colonies of C. neoformans unless the laboratory is using Staib agar or its modifications supplemented with biphenyl. As we know, AIDS patients now survive longer due to new therapies. In the final stages, invasive growth of aspergilli and Mucoraceae can start on biologically inactive material, especially lung tissue. These observations show that increasingly, the medical mycologist is obliged to assess every cultural result of materials from the inner organs in relation to the immune status of the host. Indoor air mycology deals with the clarification of ecological and epidemiological circumstances characterizing the habitats of fungi in the immediate environment of humans and animals. It also relates to the host's immunopathological status which finally allows invasiveness and growth of the fungus in a similar way to the process of composting. It is a special task for medical mycology to find the borderline between benefit and damage where opportunistic fungi are concerned, that is, between useful composting and a large-scale and costly exclusion of airborne invasive fungal infections in places where treatment methods like organ transplantation are carried out. This complex field requires a close cooperation between medical mycology, hospital pathology, immunology, allergology, soil microbiology, botany, architecture, indoor design and hygiene. Fungi in indoor soils compared to the spora of ambient air
Although the association of fungal opportunistic pathogens with potted plant soils has been shown in several studies [7, 8], no investigation has been undertaken to determine if the fungal propagules detected are indigenous to the soils themselves. Since the surfaces of potted plant soils are continuously exposed to spore fall from ambient indoor air, a possibility exists that many isolates from plant-associated surface soils simply reflect this continual sedimentation. If that were the case, a potted plant would be of no more epidemiological concern than any other dusty surface. On the other hand, if potted plants served as specialized incubators of opportunistic pathogens, they should be regarded as particularly hazardous. We therefore compared the fungal propagule assemblages of potted plant soils in a hospital with the propagule assemblages of ambient hospital air. Air sampling was conducted in areas away from the plants, thus preventing an influence of propagules derived from the plant soils on air sampling results. Air samples were taken with a two-stage Anderson sampler under both normal and disturbed (hospital renovation) conditions at all times of the year. Fungi were also isolated by dilution plating from the surface soils of the five indoor plants. Air samples and soil suspensions were cultured using Littman's oxgall medium incubated at 22.5°C and 37°C. Soil samples were also incubated on several additional media. Assemblages of isolates from plant surface soils showed remarkably little resemblance to isolates obtained from air samples. The numerically predominant species of fungal propagules in plant soils included those of the opportunistic pathogens A. fumigatus and Pseudallescheria boydii (Scedosporium apiospermum), as well as those of the nonpathogens Acremonium furcatum, Myrothecium verrucaria, Gliocladium roseum, Penicillium brevicompactum and Penicillium citreonigrum. The most common species isolated from air overall included Aspergillus ustus, Cladosporium herbamm, Acrodontium salmoneum and Penicillium oxalicum. Species regularly isolated at 37°C from air included Aspergillus ustus, A. furnigatus, Aspergillus sydowii
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and Penicillium oxalicum. Constant propagule types associated with indoor air samples during renovation-related disturbances included Penicillium chrysogenum and other members of Penicillium subgenus Penicillium. Among the human opportunistic pathogens isolated from hospital air, the most common, A. fumigatus, was proportionally more common in plant soils. It made up only 2.2% of fungi from air samples but made up 5.5% of isolates from plant soils overall, with some individual plant soil samples as high as 9.1%. A fumigatus was much more frequent in plant soils than were other common species likely to sediment out from the air onto plant soil surfaces. For example A. ustus, which was abundant throughout the hospital (20.8% of total air isolates) was never isolated from plant soils, while the ubiquitous P. chrysogenum (6.2% of air isolates) was isolated on only one occasion from a plant soil (0.1% of total plant isolates). P. boydii, the second-most-common opportunistic pathogen from plant soils (4.8% of isolates) was not isolated from air samples. Other opportunists found in plant soils but not in the air spora were Fusarium solani and Scedosporium inflatum. Analysis of conidial and spore dispersal mechanisms of species in air and plant soil samples revealed that the vast majority (99.3%) of isolates from air were of species primarily reproducing by means of dry conidia or spores. Only a minority (39.1%) of the propagules associated with plant soils belonged to these dry dispersal forms. Glioid, wet conidial types predominated in the plant soils (60.9% of total isolates) but were rare in air samples. Many of the opportunistic pathogens isolated primarily or exclusively from the plant soils (P. boydii, Fusarium oxysporum, F. solani, S. inflatum) fell into this category. The propagules present in plant soils apparently represent indigenous fungal populations, not species sedimenting out from the air. It is clear that indoor plant soils possess 'adapted and interactive communities of soil fungi' [3] in which 'spores of alien species are likely to germinate and die or be consumed long before gaining entry.' Thus, any pathogenic flora found in significant numbers in indoor plant soils can normally be considered endemic to the soils themselves. ACKNOWLEDGEMENTS Dr R. Dales thanks S. Bartlett, C. Franklin, A. P. Gilman, E. McGowan, J. D. Miller, M. Raizenne, and R. S. Tobin, while Dr R. Summerbell thanks J. Clent, P. Dyback and S. Hopyan.
CONTRIBUTORS The contributors to this symposium were: R. Dales, I-I. Zwanenburg & R. Burnett, Canadian air quality health survey: influence of home dampness and molds on respiratory health; N. Nolard, Fungi causing allergy: their ecology and significance within dwellings; F. Staib, Pathogenic fungi in human dwellings; R. C. Summerbell, S. Krajden, J. Kane, D. Fung & D. Leong, Fungi in indoor soils compared to the spora of ambient air. The co-convenors were R. Summerbell and J. Kane.
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REFERENCES 1. ANDRAE,S., AXELSON, S., BJORKSTEN,B., FREDRIKSSON,M. & KJELLMAN,N.-I. M. 1988. Symptoms of bronchial hyperreactivity and asthma in relation to environmental factors. Archives of Disease in Childhood, 63, 473-478. 2. BRUNEKREEF,B., DOCKERY,D. W., SPEIZER, F. E., WARE, J. H., SPENGLER,J. D. ~ FERRIS, B. G. 1989. Home dampness and respiratory morbidity in children. American Review of Respiratory Disease, 140, 1363-1367. 3. CHRISTENSEN,M. 1989. A view of fungal ecology. Mycologia, 81, 1-19. 4. FERRIS, B. G. 1978. Epidemiology standardization project. American Review of Respiratory Disease, 118 (Suppl.), 36-47. 5. LEBOWITZ,M. D., QUACKENBOSS,J. J., SOCZEK,M. L., COLOME,S. D. ¢~ LIOY, P. J. 1989. Workshop: Development of questionnaires and survey instruments. In: N. L. NAGDA & J. P. HARPER, (Eds) Design and protocol for monitoring indoor air quality, ASTM STP Vol. 1002, pp. 203-216. American Society for Testing and Materials, Philadelphia. 6. MARTIN,C. J., PLAIT, S. D. & HUNT, S. M. 1987. Housing conditions and ill health. British Medical Journal, 294, 1125-1127. 7. STAIB, F., TOMPAK, B., THIEL, D. & ABEL, Th. 1978. Aspergillus fumigatus in der Topferde von Zimmerpflanzen. Ein Beitrag zur Epidemiologie der Aspergillose des Menschen. Bundesgesundheits-
blatt, 21,209-213. 8. SUMMERBELL,R. C., KRAJDEN, S. & KANE, J. 1989. Potted plants in hospitals as reservoirs of pathogenic fungi. Mycopathologia, 106, 13-22. 9. TomN, R. S., BARANOWSKI,E., GILMAN, A. P., KUIPER-GOODMAN,T., MILLER, J. D. & GIDOINGS, M. 1987. Significance of fungi in indoor air: report of a working group. Canadian Journal of Public Health, 78 (Suppl.), S1-S14. 10. WARE, J. H., DOCKERY,D. W., SPIRO, A., SPEIZER, F. E. & FERRIS, B. G. 1984. Passive smoking, gas cooking and respiratory health of children living in six cities. American Review of Respiratory Disease, 129, 366--374.
Ecology of fungi in human dwellings R. C. SUMMERBELL 1,2, F. STAIB 3, R. DALES 4,5, N. N O L A R D 6, J. KANE z,7, H. Z W A N E N B U R G 4, R. B U R N E T T 4, S. K R A J D E N 2'7, D. FUNG 8 AND
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D. LEONG 8
1Mycology, Ontario Ministry of Health, Box 9000, Terminal A, Toronto, Ontario, and 2Department of Microbiology, University of Toronto, Toronto, Canada; 3Robert Koch Institut des Bundesgesundheitsamtes, Berlin, Germany; 4Health Protection Branch, Health and Welfare Canada, Ottawa, and 5University of Ottawa, Ottawa, Canada; 6Institut d'Hygidne et d'EpidOmiologie, Ministdre de la Santo Publique et de l'environnement, Brussels, Belgium; 7St. Joseph's Health Centre, Toronto, and SOccupational Health, Ontario Ministry of Labour, Toronto, Canada Human dwellings are seldom sources of invasive mycotic disease in immunocompetent persons but may harbour molds and yeasts capable of causing opportunistic infection and allergenically mediated disease. In addition, household molds have recently been associated epidemiologically with non-specific respiratory complaints of uncertain aetiology. Investigators worldwide are now exploring the connections between domestic fungi and the symptoms of non-invasive diseases such as hypersensitivity pneumonitis, and also are conducting fundamental studies on the ecology of mycotic agents of disease and allergic distress. Presented below are four topics representative of our current state of knowledge on the domestic ecology of fungi associated with morbidity and mortality. Canadian air quality health survey: influence of home dampness and moulds on respiratory health
Canadian homes, because of the cold climate, tend to be well insulated and may consequently have reduced fresh air exchange [9]. Since North Americans spend little time outside, indoor air quality is understandably an important issue. Dampness, with resulting mould growth, has been associated with non-specific respiratory symptoms in several countries. In 1988 a large questionnaire-based study was conducted to investigate this problem in Canadian homes. Six Canadian regions spanning the east to west coast were selected for study. These were: The Maritimes, Quebec, Muskoka Ontario, Southwestern Ontario, Saskatchewan and British Columbia. Within each region five agricultural service towns were selected, none of which had local industrial sources of outdoor air pollution. Children who attended kindergarten to grade three, between March and April 1988, were eligible to receive questionnaires to be completed by the parent or guardian most familiar with the child's health. The questionnaire questions used in the present study were taken or modified from the American Thoracic Society - Division of Lung Disease Respiratory Symptom Questionnaire, used by the Harvard School of Public Health in the six city 279
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study, and the Basic Standard Environmental Inventory Questionnaire developed by Lebowitz et al. [4, 5, 10]. Home dampness/mold was defined as the reported presence of wet or damp spots on inside surfaces, leaking or flooding in the basement, and mould or mildew growing inside the home. Lower respiratory symptoms were defined as the report of any of; cough, phlegm, wheeze, or wheeze with dyspnea in adults. In children, the definition was similar except that persistent phlegm was not included. A total of 17 962 parents or guardians received a questionnaire and 14 948 (83%) were returned. A total of 12 569 children between the ages of 5 and 8 years, and 14 799 adults, at least 21 years of age, were available for analysis. Reported prevalence of home dampness/mould was 38%. Symptom prevalence among children was 19.5% versus 13.2%, among those with and without reported home dampness/mould. Corresponding values for adults were: 38% versus 27% among current smokers, 21% versus 14% for ex-smokers, and 19% versus 11% for individuals who had never smoked. The corresponding adjusted odds ratio for children was 1.50 (95% CI 1.35, 1.67), and for adults combining smoking categories was 1.62 (95% CI 1.48, 1.78). We found that home dampness and mould were associated with increased respiratory symptoms among both adults and children. The findings persisted despite adjustment for other influencing variables and were consistent with studies from other countries [1, 2, 6]. The reported prevalence of home dampness or moulds in Canadian homes, approximately 38%, indicates that it is an important public health issue. Further studies are required to elucidate the symptom pathogenesis.
Fungi causing allergy: their ecology and significance within dwellings Since the first world oil crisis in the 1970s, Belgium has seen a continuing increase in complaints of an allergic nature correlated with habitat. Indeed, in order to reduce energy costs due to the heating of homes, under pressure from the public authorities, people have begun to renovate their houses with the aim of best insulating every part, from the cellar to the attic. This has been done so relentlessly that, in Belgium, the public authorities have created grants 'for renovation' which are accorded only in relation to the degree of energy saving attained by the transformations. In addition, the effectiveness of the insulation has since become one of the major selling points in the choice of a new house. However, excessive insulation has the effect of exposing allergic individuals to numerous irritants, favouring as it does, through lack of ventilation and renewal of air, the development of numerous moulds. Amongst these are numerous species whose allergenicity had not been tested previously. Our laboratory at the Institute of Hygiene in Brussels has developed a scheme for 'environmental control in the home' which is based on the survey of about 120 homes belonging to allergic patients. This environmental control includes the sampiing itself (air, surface and dust control), the isolation, purification and the placing in the collection of strains destined for immunological testing (more than 2000 strains are either conserved lyophilised or under liquid nitrogen in the IHEM, Brussels collection), the creation of a serum bank containing sera from people living in the environment studied, the standardisation of a mini-method for preparing fungal extracts and, finally, the immunological analysis of sera from allergic patients, from
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subjects exposed to the same environment but not symptomatic and from a pool of test sera. Results indicate that most of the indoor allergenic fungi are not catered for by commercially available extracts and that one must not underestimate the importance of fungi in the home as the cause of type III allergies. The results of these studies have revealed that the sites more often contaminated in the home are: kitchens and bath rooms (Cladosporium cladosporioides, Cladospor-
ium sphaerospermum, Ulocladium botrytis, Chaetomium globosum, Aspergillus fumigatus); wallpaper (C. sphaerospermum, Chaetomium species, Doratomyces species, Fusarium species, Stachybotrys atra, Trichoderma species, Scopulariopsis species); mattresses, carpets (PeniciUium species, Aspergillus versicolor, Aureobasidium pullulans, Aspergillus repens, Wallemia sebi, Chaetomium species); window-frames (A. pullulans, C. sphaerospermum, Ulocladium species); cellars and crawl spaces (A. versicolor, A. fumigatus, Fusarium species); the soil of ornamental plants (A. fumigatus, Aspergillus niger and Aspergillus flavus); insulation material (A. versicolor, A. fumigatus, Fusarium species). Pathogenic fungi in human dwellings There is a difference between dwellings in the zones of temperate and tropical climates. In an area of temperate climate like Germany, the subject of pathogenic fungi in human dwellings has nothing to do with infections of the immunocompetent host, but rather with infections connected to immunosuppressive therapy or defined immunodeficiencies. Of prime interest are airborne invasive infections of such highrisk patients by fungi occupying habitats within dwellings such as private houses or hospitals. The most important agents of mycotic infection in immunodeficient persons are some Aspergillus species, some species of Mucoraceae, and Cryptococcus neoforroans. Together with other micro-organisms, these fungi are normally vigorous decomposers of various types of detritus. The indoor habitats of Aspergillus species and Mucoraceae include the soil of potted indoor plants. Our observations on the high frequency of Aspergillus species in the soil of indoor plants and on their possible epidemiological role in hospitals were confirmed by the thorough investigations of Summerbell et al. [8]. Mucoraceae such as Rhizopus, Rhizomucor, Absidia and Mucor species could also be isolated by us from the soil of potted plants. Additionally, we have found that the growth of polyene-producing streptomycetes in the rhizosphere of a potted plant may influence the presence or absence of particular fungal agents, a result which is of strong ecological and epidemiological interest. Neutropenic patients exposed to soil of potted plants in the hospital may become infected by A. furnigatus, A. niger, A. flavus, Absidia corymbifera and Rhizopus species. Proving the source of such an infection will always be difficult. In fatal cases where identical combinations of two or three fungi (e.g.A. fumigatus, A. flavus and A. corymbifera) have been isolated from autopsy material and from the soil of the plant next to the patient, a probable association has been inferred. Air sampling has been of great help in such studies. Other probable sources of fatal Aspergillus infections of hospitalized neutropenic patients included other patients with aspergillosis in the hospital, food products like nuts, uncooked dry vegetarian food, and spices such as pepper, neglected hydro-
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culture plants, ventilation systems and construction dust. In one diabetic patient, the probable source of rhinocerebral infection by Rhizopus oryzae was 'cat grass' heavily colonized by this fungus in the patient's living room. Our investigations of the 'biological waste container' newly introduced in Germany have shown that in the very first stage of composting during the collection of waste in the household (about 1 week), A. fumigatus and Mucoraceae grow and may become a focus of air contamination and a source of infection for immunocompromised persons. C. neoformans vat. neoformans in nature is specialized to degrade concentrated, relatively bacteria-free bird urine, therefore, habitats of this yeast are not as widespread as those of aspergilli and Mucoraceae in our environment. This may also be the reason why C. neoformans infections do not occur with a frequency that could be expected in view of the number of persons with an immunopathological predisposition for cryptococcosis (e.g. only 3-5% of AIDS patients are positive). In Berlin, approximately 1-6% of bird cages have been found to be positive for C. neoformans var. neoformans and the droppings of feral pigeons in 7% of sheltered places such as church spires. C. neoformans var. gattii was never isolated from bird droppings. In Berlin, C. neoformans is not found outdoors. Since 1983 all strains from the droppings of caged birds examined produced a weak creatinine auxanogram and proved to be serotype A, while those of pigeons which produced intense creatinine auxanograms proved to be of either serotype A or D (serotyping was performed by Dr J. Kwon-Chung). Surprisingly, there have been no reports of nosocomial infections by C. neoformans, although this fungus may be excreted in the urine of AIDS patients in high quantities (due to the symptom-free involvement of the prostate as an ecological niche for C. neoformans). There is a question as to whether the basidiospore of the perfect state of C. neoformans, namely FilobasidieUa neoformans, is the only infective particle of C. neoformans. Our experiments using bird manure filtrate agar with two compatible strains of C. neoformans showed that constituents of bird urine may support the formation of the perfect state with basidiospore development within 48 h. We have made epidemiological--ecological and diagnostic observations on Aspergillus species, Mucoraceae and C. neoformans var. neoformans in indoor air with the aid of the Reuter centrifugal air sampler in combination with Staib agar + penicillin + streptomycin as a differential medium (syn. Guizotia abyssinica creatinine agar, bird seed agar). In volaries of caged birds in the Berlin zoo, approximately 100 colony forming units (c.f.u.) of Aspergillus species, approximately 40 c.f.u, of Mucoraceae and five c.f.u, of C. neoformans could be isolated from 40 1 of aspirated air. C. neoformans could only be detected when the growth of aspergilli and Mucoraceae was inhibited by addition of biphenyl to Staib agar. Similar proportions of the total c.f.u, counts were found to represent these three different groups of fungi at a number of similar sites. This result shows that a fungus of special epidemiological interest like C. neoformans may be accompanied in air samples by a characteristic assemblage of micro-organisms, all possibly growing within the same habitat and reflecting the stage of decomposition of material in the focus of origin. From the standpoint of pathogenesis, in the case of a person in the primary stage of AIDS inhaling this air, only C. neoformans will start an airborne infection but not the propagules of aspergilli or Mucoraceae. These fungi only cause confusion when the bronchial lavage of persons with AIDS is cultured. In addition, these
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moulds can overgrow the rare colonies of C. neoformans unless the laboratory is using Staib agar or its modifications supplemented with biphenyl. As we know, AIDS patients now survive longer due to new therapies. In the final stages, invasive growth of aspergilli and Mucoraceae can start on biologically inactive material, especially lung tissue. These observations show that increasingly, the medical mycologist is obliged to assess every cultural result of materials from the inner organs in relation to the immune status of the host. Indoor air mycology deals with the clarification of ecological and epidemiological circumstances characterizing the habitats of fungi in the immediate environment of humans and animals. It also relates to the host's immunopathological status which finally allows invasiveness and growth of the fungus in a similar way to the process of composting. It is a special task for medical mycology to find the borderline between benefit and damage where opportunistic fungi are concerned, that is, between useful composting and a large-scale and costly exclusion of airborne invasive fungal infections in places where treatment methods like organ transplantation are carried out. This complex field requires a close cooperation between medical mycology, hospital pathology, immunology, allergology, soil microbiology, botany, architecture, indoor design and hygiene. Fungi in indoor soils compared to the spora of ambient air
Although the association of fungal opportunistic pathogens with potted plant soils has been shown in several studies [7, 8], no investigation has been undertaken to determine if the fungal propagules detected are indigenous to the soils themselves. Since the surfaces of potted plant soils are continuously exposed to spore fall from ambient indoor air, a possibility exists that many isolates from plant-associated surface soils simply reflect this continual sedimentation. If that were the case, a potted plant would be of no more epidemiological concern than any other dusty surface. On the other hand, if potted plants served as specialized incubators of opportunistic pathogens, they should be regarded as particularly hazardous. We therefore compared the fungal propagule assemblages of potted plant soils in a hospital with the propagule assemblages of ambient hospital air. Air sampling was conducted in areas away from the plants, thus preventing an influence of propagules derived from the plant soils on air sampling results. Air samples were taken with a two-stage Anderson sampler under both normal and disturbed (hospital renovation) conditions at all times of the year. Fungi were also isolated by dilution plating from the surface soils of the five indoor plants. Air samples and soil suspensions were cultured using Littman's oxgall medium incubated at 22.5°C and 37°C. Soil samples were also incubated on several additional media. Assemblages of isolates from plant surface soils showed remarkably little resemblance to isolates obtained from air samples. The numerically predominant species of fungal propagules in plant soils included those of the opportunistic pathogens A. fumigatus and Pseudallescheria boydii (Scedosporium apiospermum), as well as those of the nonpathogens Acremonium furcatum, Myrothecium verrucaria, Gliocladium roseum, Penicillium brevicompactum and Penicillium citreonigrum. The most common species isolated from air overall included Aspergillus ustus, Cladosporium herbamm, Acrodontium salmoneum and Penicillium oxalicum. Species regularly isolated at 37°C from air included Aspergillus ustus, A. furnigatus, Aspergillus sydowii
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and Penicillium oxalicum. Constant propagule types associated with indoor air samples during renovation-related disturbances included Penicillium chrysogenum and other members of Penicillium subgenus Penicillium. Among the human opportunistic pathogens isolated from hospital air, the most common, A. fumigatus, was proportionally more common in plant soils. It made up only 2.2% of fungi from air samples but made up 5.5% of isolates from plant soils overall, with some individual plant soil samples as high as 9.1%. A fumigatus was much more frequent in plant soils than were other common species likely to sediment out from the air onto plant soil surfaces. For example A. ustus, which was abundant throughout the hospital (20.8% of total air isolates) was never isolated from plant soils, while the ubiquitous P. chrysogenum (6.2% of air isolates) was isolated on only one occasion from a plant soil (0.1% of total plant isolates). P. boydii, the second-most-common opportunistic pathogen from plant soils (4.8% of isolates) was not isolated from air samples. Other opportunists found in plant soils but not in the air spora were Fusarium solani and Scedosporium inflatum. Analysis of conidial and spore dispersal mechanisms of species in air and plant soil samples revealed that the vast majority (99.3%) of isolates from air were of species primarily reproducing by means of dry conidia or spores. Only a minority (39.1%) of the propagules associated with plant soils belonged to these dry dispersal forms. Glioid, wet conidial types predominated in the plant soils (60.9% of total isolates) but were rare in air samples. Many of the opportunistic pathogens isolated primarily or exclusively from the plant soils (P. boydii, Fusarium oxysporum, F. solani, S. inflatum) fell into this category. The propagules present in plant soils apparently represent indigenous fungal populations, not species sedimenting out from the air. It is clear that indoor plant soils possess 'adapted and interactive communities of soil fungi' [3] in which 'spores of alien species are likely to germinate and die or be consumed long before gaining entry.' Thus, any pathogenic flora found in significant numbers in indoor plant soils can normally be considered endemic to the soils themselves. ACKNOWLEDGEMENTS Dr R. Dales thanks S. Bartlett, C. Franklin, A. P. Gilman, E. McGowan, J. D. Miller, M. Raizenne, and R. S. Tobin, while Dr R. Summerbell thanks J. Clent, P. Dyback and S. Hopyan.
CONTRIBUTORS The contributors to this symposium were: R. Dales, I-I. Zwanenburg & R. Burnett, Canadian air quality health survey: influence of home dampness and molds on respiratory health; N. Nolard, Fungi causing allergy: their ecology and significance within dwellings; F. Staib, Pathogenic fungi in human dwellings; R. C. Summerbell, S. Krajden, J. Kane, D. Fung & D. Leong, Fungi in indoor soils compared to the spora of ambient air. The co-convenors were R. Summerbell and J. Kane.
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