Bacillus licheniformis in geogenic dust induces inflammation in respiratory epithelium.

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  • Additional Information
    • Source:
      Publisher: Elsevier Country of Publication: Netherlands NLM ID: 0147621 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1096-0953 (Electronic) Linking ISSN: 00139351 NLM ISO Abbreviation: Environ Res Subsets: MEDLINE
    • Publication Information:
      Publication: <2000- > : Amsterdam : Elsevier
      Original Publication: New York, Academic Press.
    • Subject Terms:
      Bacillus licheniformis* ; Dust* ; Inflammation* ; Respiratory Mucosa*/microbiology; Animals ; Australia ; Humans ; Mice
    • Abstract:
      Exposure to environmental geogenic (or earth-derived) dust can lead to more frequent and severe infections in the human airway. Particulate matter < 10 µm (PM 10 ) is the component of air pollution that is commonly associated with the exacerbation of respiratory diseases. We have previously demonstrated that mice exposed to geogenic dust PM 10 experienced an exacerbation of inflammatory responses to influenza A virus. Whether geogenic dust PM 10 also exacerbates respiratory bacterial infection is not yet known, nor are the components of the dust that drive these responses. We treated airway bronchial epithelial cells (NuLi-1) with UV-irradiated geogenic dust PM 10 from six remote Western Australian towns. High levels of IL-6 and IL-8 production were observed, as well as persistent microbial growth. 16 S rRNA sequencing of the growth identified the microbe as Bacillus licheniformis, a spore-forming, environmentally abundant bacterium. We next investigated the interaction of B. licheniformis with respiratory epithelium in vitro to determine whether this exacerbated infection with a bacterial respiratory pathogen (non-typeable Haemophilus influenzae, NTHi). Heat treatment (100 °C) of all PM 10 samples eliminated B. licheniformis contamination and reduced epithelial inflammatory responses, suggesting that heat-labile and/or microbial factors were involved in the host response to geogenic dust PM 10 . We then exposed NuLi-1 epithelium to increasing doses of the isolated Bacillus licheniformis (multiplicity of infection of 10:1, 1:1 or 0.1:1 bacteria: cells) for 1, 3, and 24 h. B. licheniformis and NTHi infection (association and invasion) was assessed using a standard gentamicin survival assay, and epithelial release of IL-6 and IL-8 was measured using a bead based immunoassay. B. licheniformis was cytotoxic to NuLi-1 cells at 24 h. At 3 h post-challenge, B. licheniformis elicited high IL-6 and IL-8 inflammatory responses from NuLi-1 cells compared with cells treated with heat-treated geogenic dust PM 10 (p < 0.0001). Whilst treatment of cells with B. licheniformis increased inflammation, this did not make the cells more susceptible to NTHi infection. This study highlights that geogenic dust PM 10 can harbour viable bacterial spores that induce inflammation in respiratory epithelium. The impact on respiratory health from inhalation of bacterial spores in PM 10 in arid environments may be underestimated. Further investigation into the contribution of B. licheniformis and the wider dust microbiome to respiratory infection is warranted.
      (Copyright © 2018 Elsevier Inc. All rights reserved.)
    • Contributed Indexing:
      Keywords: Bacillus licheniformis; Geogenic dust PM(10); Infection; Non-typeable Haemophilus influenzae; Respiratory
    • Accession Number:
      0 (Dust)
    • Publication Date:
      Date Created: 20180310 Date Completed: 20190827 Latest Revision: 20190827
    • Publication Date:
      20221213
    • Accession Number:
      10.1016/j.envres.2018.02.025
    • Accession Number:
      29522999