Geogenic particles induce bronchial susceptibility to non-typeable Haemophilus influenzae

Lewis J Williams; Stephen G Tristram; Graeme R Zosky

doi:10.1016/j.envres.2023.116868

Geogenic particles induce bronchial susceptibility to non-typeable Haemophilus influenzae

Environ Res. 2023 Nov 1;236(Pt 2):116868. doi: 10.1016/j.envres.2023.116868. Epub 2023 Aug 9.

Authors

Lewis J Williams¹, Stephen G Tristram², Graeme R Zosky³

Affiliations

¹ Tasmanian School of Medicine, University of Tasmania, Hobart, 7000, Australia.
² School of Health Sciences, University of Tasmania, Launceston, 7250, Australia.
³ Tasmanian School of Medicine, University of Tasmania, Hobart, 7000, Australia; Menzies Institute for Medical Research, University of Tasmania, Hobart, 7000, Australia. Electronic address: graeme.zosky@utas.edu.au.

PMID: 37567381
DOI: 10.1016/j.envres.2023.116868

Abstract

Exposure to geogenic (earth-derived) particulate matter (PM) is linked to an increased prevalence of bronchiectasis and other respiratory infections in Australian Indigenous communities. Experimental studies have shown that the concentration of iron in geogenic PM is associated with the magnitude of respiratory health effects, however, the mechanism is unclear. We investigated the effect of geogenic PM and iron oxide on the invasiveness of non-typeable Haemophilus influenzae (NTHi). Peripheral blood mononuclear cell-derived macrophages or epithelial cell lines (A549 & BEAS-2B) were exposed to whole geogenic PM, their primary constituents (haematite, magnetite or silica) or diesel exhaust particles (DEP). The uptake of bacteria was quantified by flow cytometry and whole genome sequencing (WGS) was performed on NTHi strains. Geogenic PM increased the invasiveness of NTHi in bronchial epithelial cells. Of the primary constituents, haematite also increased NTHi invasion with magnetite and silica having significantly less impact. Furthermore, we observed varying levels of invasiveness amongst NTHi isolates. WGS analysis suggested isolates with more genes associated with heme acquisition were more virulent in BEAS-2B cells. The present study suggests that geogenic particles can increase the susceptibility of bronchial epithelial cells to select bacterial pathogens in vitro, a response primarily driven by haematite content in the dust. This demonstrates a potential mechanism linking exposure to iron-laden geogenic PM and high rates of chronic respiratory infections in remote communities in arid environments.

Keywords: Bronchiectasis; Geogenic PM; Iron oxide; Non-typeable Haemophilus influenzae (NTHi); Particulate matter.