Synergistic interaction in simultaneous exposure to Streptomyces californicus and Stachybotrys chartarum.

Abstract

The microbial exposure associated with health complaints in moldy houses consists of a heterogeneous group of components, including both living and dead bacteria, fungi, and their metabolites and active compounds. However, little is known about the interactions between different microbes and their metabolites, although the cytotoxicity and inflammatory potential of certain individual microbes have been reported. In this study, we investigated the inflammatory responses of mouse RAW264.7 macrophages after exposure to six indoor air microbes (Aspergillus versicolor, Penicillium spinulosum, Stachybotrys chartarum, Bacillus cereus, Mycobacterium terrae, and Pseudomonas fluorescens) alone and together with the actinomycete Streptomyces californicus. The production of nitric oxide, levels of the proinflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6), and cytotoxicity were measured. The coexposure to Sta. chartarum and Str. californicus caused a synergistic increase in the production of IL-6 but not other cytokines. In further experiments, the metabolites from Sta. chartarum or from closely related fungi (atranones B and E, satratoxin G, trichodermin, 7-α-hydroxytrichodermol, staplabin, and SMTP-7) and the known fungal toxins sterigmatocystin, citrinin, and ochratoxin A were each tested with Str. californicus. The testing revealed a synergistic response in TNF-α and IL-6 production after coexposure to Str. californicus with both trichodermin and 7-α-hydroxytrichodermol. Finally, the synergistic inflammatory response caused by Str. californicus and trichodermin together was studied by analyzing for the presence of nuclear factor-κB (NF-κB) in nuclear extracts of the exposed cells. The exposure to Str. californicus induced the binding of NF-κB proteins to the NF-κB consensus sequence as well as to the natural NF-κB site of the IL-6 promoter. Adding trichodermin to the exposure did not increase the DNA binding.

Bacterial-Fungal Interactions: Hyphens between Agricultural, Clinical, Environmental, and Food Microbiologists

“…These mixed biofilms, which have also been evidenced with C. albicans (195,289), can be more resistant to antibiotic treatments; for example, the presence of Staphylococcus epidermidis was shown to delay the diffusion of antifungal drugs in mixed Candida-Staphylococcus biofilms (6). Bacterial-fungal associations with potentially detrimental impacts on human health may also occur in moldy houses (170). In these damp environments, actinobacteria frequently cohabit with fungal genera associated with moisture damage, such as Stachybotrys and Aspergillus.…”

“…In these damp environments, actinobacteria frequently cohabit with fungal genera associated with moisture damage, such as Stachybotrys and Aspergillus. Research evaluating the impact of such BFIs in cell lines indicates a significant potential for synergistic effects between these bacteria and fungi on cytotoxicity and mammalian inflammatory responses (170,267,304,305). While mixed bacterial-fungal communities have been shown to have detrimental effects on human health, to our knowledge, there have been no reports describing the roles of intrahyphal bacteria in fungal infections of humans.…”

Analysis of Fungal Flora in Indoor Dust by Ribosomal DNA Sequence Analysis, Quantitative PCR, and Culture

“…Several microbial indicators have been suggested to associate with moisture damage and/or health complaints (13,27,33,39,46,58), yet a consensus regarding their causative role in relation to the health effects is lacking. The potential harmfulness of microbial contamination is suggested to be dependent on the species content and concurrently occurring species combinations, as well as on the material and growth conditions in which the microbial proliferation occurred (19,31,53,59,71).…”

Targeted Inspection of Environmental Mycological Load for Mitigation of Indoor Mold toward Improved Public Health

“…The skin or gastrointestinal tract may become infested with mold and fungal substrates, and inhalation of fungal units and spore-borne toxins are important sources of exposure [7]. Nevertheless, health problems caused by inhaled mycotoxins tend to be more serious than those caused by mycotoxins absorbed via the digestive tract or skin [13][14][15][16]. Creasia et al [25] showed that mycotoxins can be 10 times more toxic through inhalation than by systemic administration in mice.…”

“…Other groups at risk, such as the elderly [9] and young children [10,11], have been noted for their susceptibility to the harmful effects of indoor air and fungi. Both direct fungal infection (mycosis) [7] and toxigenic effects of fungal mycotoxins have been reported [12][13][14][15][16].…”