Inflammatory potential of the spores of Penicillium spinulosum isolated from indoor air of a moisture-damaged building in mouse lungs

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

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

International Space Station environmental microbiome - microbial inventories of ISS filter debris

Despite an expanding array of molecular approaches for detecting microorganisms in a given sample, rapid and robust means of assessing the differential viability of the microbial cells, as a function of phylogenetic lineage, remain elusive. A propidium monoazide (PMA) treatment coupled with downstream quantitative polymerase chain reaction (qPCR) and pyrosequencing analyses was carried out to better understand the frequency, diversity, and distribution of viable microorganisms associated with debris collected from the crew quarters of the International Space Station (ISS). The cultured bacterial counts were more in the ISS samples than cultured fungal population. The rapid molecular analyses targeted to estimate viable population exhibited 5-fold increase in bacterial (qPCR-PMA assay) and 25-fold increase in microbial (adenosine triphosphate assay) burden than the cultured bacterial population. The ribosomal nucleic acid-based identification of cultivated strains revealed the presence of only four to eight bacterial species in the ISS samples, however, the viable bacterial diversity detected by the PMA-pyrosequencing method was far more diverse (12 to 23 bacterial taxa) with the majority consisting of members of actinobacterial genera (Propionibacterium, Corynebacterium) and Staphylococcus. Sample fractions not treated with PMA (inclusive of both live and dead cells) yielded a great abundance of highly diverse bacterial (94 to 118 taxa) and fungal lineages (41 taxa). Even though deep sequencing capability of the molecular analysis widened the understanding about the microbial diversity, the cultivation assay also proved to be essential since some of the spore-forming microorganisms were detected only by the culture-based method. Presented here are the findings of the first comprehensive effort to assess the viability of microbial cells associated with ISS surfaces, and correlate differential viability with phylogenetic affiliation.

Murine models of airway fungal exposure and allergic sensitization

Inhalation of common indoor filamentous fungi has been associated with the induction or exacerbation of allergic respiratory disease. The understanding of fungal inhalation and allergic sensitization has significantly advanced with the use of small animal models, especially mouse models. Numerous studies have employed different animal exposure and sensitization techniques, each with inherent advantages and disadvantages that are addressed in this review. In addition, most studies involve exposure of animals to fungal spores or spore extracts while neglecting the influence of hyphal or subcellular fragment exposures. Recent literature examining the potential for hyphae and fungal fragments to induce or exacerbate allergy is discussed. Innate immune recognition of fungal elements and their contribution to lung allergic inflammation in animal models are also reviewed. Though physical properties of fungi play an important role following exposure, host immune development is also critical in airway inflammation and allergy. We discuss the importance of environmental factors that influence early immune development and subsequent susceptibility to allergy. Murine studies that examine the role of intestinal microflora and prenatal or early life environmental factors that promote allergic sensitization are also evaluated. Future studies will require animal models that accurately reflect natural fungal exposures and identify environmental factors that influence immune development and thus promote respiratory fungal allergy and disease.

Fungal spores: a critical review of the toxicological and epidemiological evidence as a basis for occupational exposure limit setting

Fungal spores are ubiquitous in the environment. However, exposure levels in workplaces where mouldy materials are handled are much higher than in common indoor and outdoor environments. Spores of all tested species induced inflammation in experimental studies. The response to mycotoxin-producing and pathogenic species was much stronger. In animal studies, nonallergic responses dominated after a single dose. Allergic responses also occurred, especially to mycotoxin-producing and pathogenic species, and after repeated exposures. Inhalation of a single spore dose by subjects with sick building syndrome indicated no observed effect levels of 4 x 10(3) Trichoderma harzianum spores/m(3) and 8 x 10(3) Penicillium chrysogenum spores/m(3) for lung function, respiratory symptoms, and inflammatory cells in the blood. In asthmatic patients allergic to Penicillium sp. or Alternaria alternata, lowest observed effect levels (LOELs) for reduced airway conductance were 1 x 10(4) and 2 x 10(4) spores/m(3), respectively. In epidemiological studies of highly exposed working populations lung function decline, respiratory symptoms and airway inflammation began to appear at exposure levels of 10(5) spores/m(3). Thus, human challenge and epidemiological studies support fairly consistent LOELs of approximately 10(5) spores/m(3) for diverse fungal species in nonsensitised populations. Mycotoxin-producing and pathogenic species have to be detected specifically, however, because of their higher toxicity.

Effects of co-culture of amoebae with indoor microbes on their cytotoxic and proinflammatory potential

Free-living amoebae are ubiquitous environmental protozoa found in both natural and man-made environments, including moisture-damaged buildings. Furthermore, the interaction between amoebae and bacteria has been shown to enhance the virulence and pathogenicity of some bacteria. While the inhabitants of moisture damaged buildings are known to be at risk of suffering adverse health effects, the exact causative agents and mechanisms are still obscure. To examine the possible role of amoebae in the health effects associated with moisture damages, the effects of amoebae on the cytotoxicity and proinflammatory potential of nonpathogenic microbes common in moisture-damaged buildings were investigated. First, two bacterial and three fungal strains were cultured both individually and in coculture with Acanthamoeba polyphaga. Then, mouse RAW264.7 macrophages were exposed to the cocultures as well as the individually grown bacteria, fungi, and amoebae. Finally, cell viability and production of proinflammatory mediators, i.e., nitric oxide (NO), tumor necrosis factor alpha (TNF-alpha), and interleukin 6 (IL-6), were measured in macrophages after the exposure. The results revealed that cocultivation with amoebae increased the cytotoxicity of the bacterium Streptomyces californicus and the fungus Penicillium spinulosum. Moreover, the macrophages produced up to 10 times higher concentrations of NO after the exposure to these cocultures than after the exposure to individually grown microbes. Finally, the production of the cytokines was up to two orders of magnitude higher (IL-6) and up to four times higher (TNF-alpha) after exposure to the cocultures when compared to individually grown microbes. We conclude that amoebae are able to potentiate the cytotoxicity and proinflammatory properties of certain microbes associated with moisture damages.

Comparison of inflammatory responses in mouse lungs exposed to atranones A and C from Stachybotrys chartarum

Stachybotrys chartarum isolates can be separated into two distinct chemotypes based on the toxins they produce. One chemotype produces macrocyclic trichothecenes; the other produces atranones (and sometimes simple trichothecenes, e.g., trichodermol and trichodermin). Studies using in vivo models of lung disease revealed that exposure to spores of the atranone producing S. chartarum isolates led to a variety of immunotoxic, inflammatory, and other pathological changes. However, it is unclear from these studies what role the pure atranone toxins sequestered in spores of these isolates exert on lung disease onset. This study examined dose-response (0.2, 1.0, 2.0, 5.0, or 20 microg atranone/animal) and time-course (3, 6, 24, and 48 h postinstillation [PI]) relationships associated with inflammatory cell and proinflammatory chemokine/cytokine responses in mouse lungs intratracheally instilled with two pure atranones (either A or C) isolated from S. chartarum. High doses (2.0 to 20 microg toxin/animal) of atranone A and C induced significant inflammatory responses manifested as differentially elevated macrophage, neutrophil, macrophage inflammatory protein (MIP)-2, tumor necrosis factor (TNF) and interleukin (IL)-6 concentrations in the bronchioalveolar lavage fluid (BALF) of intratracheally exposed mice. Compared to controls, BALF macrophage and neutrophil numbers were increased to significant levels from 6 to 48 h (PI). Except for macrophage numbers in atranone A treatment animals, cells exhibited significant dose dependent-like responses. The chemokine/cytokine marker responses were significantly and dose-dependently increased from 3 to 24 h PI and declined to nonsignificant levels at 48 h PI. The results suggest not only that atranones are inflammatory but also that they exhibit different inflammatory potency with different toxicokinetics. Data also suggest that exposure to these toxins in spores of S. chartarum in contaminated building environments could contribute to inflammatory lung disease onset in susceptible individuals.

Comparison of immunomodulator mRNA and protein expression in the lungs of Stachybotrys chartarum spore-exposed mice

Stachybotrys chartarum is an important toxigenic fungus that has been associated with respiratory disease onset in animals and humans. It can be separated into macrocyclic trichothecene-producing and nonproducing chemotypes based on secondary metabolite production. However, effects of spores of the two chemotypes on lung inflammatory responses are poorly understood. In this study, real-time reverse-transcription polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assay (ELISA) were used to investigate time-course (1, 3, 6, 24, and 48 h post-instillation [PI]) relationships in mice intratracheally exposed to 300 spores/g body weight of a macrocyclic trichothecene-producing (JS 58-17) and a nonproducing (JS 58-06) S. chartarum isolate and of Cladosporium cladosporioides. There were marked differences in the magnitude and temporal patterns of mouse lung immune responses to intratracheal exposure to spores of these species at this spore dose. Both macrophage inflammatory protein 2 (MIP-2) and surfactant protein-D (SP-D) mRNA expression were significantly upregulated in lungs of JS 58-17-treated animals compared to that of all other treatment animals at 6 and 24 h PI. Heightened mRNA expression of these immunomodulators combined with comparatively depressed MIP-2 and tumor necrosis factor (TNF)-a protein expression suggests that the action of macrocyclic trichothecenes sequestered in 58-17 spores is involved. Interestingly, TNF-a protein expression in all spore treatment animal groups was also significantly increased over that in saline controls. Similarities in expression among all spore treatment animals suggest that chemicals other than toxic secondary metabolites, and possibly spore-sequestered 1,3-beta-D-glucan, may contribute to lung pathogenesis.

Inflammatory and Cytotoxic Responses in Mouse Lungs Exposed to Purified Toxins from Building Isolated Penicillium brevicompactum Dierckx and P. chrysogenum Thom

In vitro and in vivo studies have shown that building-associated Penicillium spores and spore extracts can induce significant inflammatory responses in lung cells and animal models of lung disease. However, because spores and spore extracts comprise mixtures of bioactive constituents often including toxins, it is impossible to resolve which constituent mediates inflammatory responses. This study examined dose-response (0.5 nM, 2.5 nM, 5.0 nM, 12.5 nM/g body weight (BW) animal) and time-course (3, 6, 24 and 48 h post instillation (PI)) relationships associated with inflammatory and cytotoxic responses in mouse lungs intratracheally instilled with pure brevianamide A, mycophenolic acid, and roquefortine C. High doses (5.0 nM and/or 12.5 nM/g BW animal) of brevianamide A and mycophenolic acid, the dominant metabolites of P. brevicompactum, and roquefortine C, the dominant metabolite of P. chrysogenum, induced significant inflammatory responses within 6 h PI, expressed as differentially elevated macrophage, neutrophil, MIP-2, TNF, and IL-6 concentrations in the bronchioalveolar lavage fluid (BALF) of intratracheally exposed mice. Macrophage and neutrophil numbers were maximal at 24 h PI; responses of the other inflammatory markers were maximal at 6 h PI. Except for macrophage numbers in mycophenolic acid-treatment animals, cells exhibited significant dose-dependent-like responses; for the chemo-/cytokine markers, dose dependency was lacking except for MIP-2 concentration in brevianamide A-treatment animals. It was also found that brevianamide A induced cytotoxicity expressed as significantly increased LDH concentration in mouse BALF, at concentrations of 12.5 nM/g BW animal and at 6 and 24 h PI. Albumin concentrations, measured as a nonspecific marker of vascular leakage, were significantly elevated in the BALF of mice treated with 12.5 nM/g nM brevianamide A/animal from 6 to 24 h PI and in > or =5.0 nM/g mycophenolic acid-treated animals at 6 to 24 h PI. These results suggest that these three toxins from Penicillium species common on damp materials in residential housing provoke compound-specific toxic responses with different toxicokinetics. Moreover, that these toxins can stimulate significant inflammatory responses in vivo might help explain some of the indoor effects associated with Penicillium spore exposures in indoor environments.

The proportions of Streptomyces californicus and Stachybotrys chartarum in simultaneous exposure affect inflammatory responses in mouse RAW264.7 macrophages

Adverse health outcomes associated with moisture-damaged buildings originate from an exposure consisting of complex interactions between various microbial species and other indoor pollutants. The concentrations and proportions of microbial components in such environments can vary greatly with the growth conditions. In this study, we aimed to evaluate the effects of simultaneous exposure with modified proportions of actinobacteria Streptomyces californicus and fungi Stachybotrys chartarum on inflammatory responses (cytokines macrophage inflammatory protein 2 [MIP2], interleukin 6 [IL-6] and tumor necrosis factor a [TNFa]; nitric oxide) and cytotoxicity (MTT-test and DNA content analysis) in mouse RAW264.7 macrophage cell line. Five different proportions of microbial spores were studied (Str. californicus: S. chartarum 10:1; 5:1; 1:1; 1:5; 1:10). RAW264.7 cells were coexposed to the total dose of 3x10(5) spores/ml for 24 h and also both of these microbial spores on their own at the respective doses. At least the 1.5-fold synergistic increase in cytokine production of RAW264.7 macrophages was detected when coexposure contained an equal amount or more fungal spores (S. chartarum) than bacterial spores (Str. californicus) compared to the sum response caused by these microbial spores separately. On the contrary, NO production after coexposure was nearly 40% less than the sum response induced by the microbial spores separately, when coexposure contains 5 times more bacterial than fungal spores. In addition, coexposure slightly changed the cytotoxic potency of the spores. The present results revealed that mutual proportions of fungal and bacterial spores in simultaneous exposure affect the nature of their interactions leading to increased or suppressed production of inflammatory mediators in RAW264.7 macrophages.