Burkholderia pseudomallei invades the olfactory nerve and bulb after epithelial injury in mice and causes the formation of multinucleated giant glial cells in vitro

PLoS Negl Trop Dis. 2020 Jan 24;14(1):e0008017. doi: 10.1371/journal.pntd.0008017. eCollection 2020 Jan.

Abstract

The infectious disease melioidosis is caused by the bacterium Burkholderia pseudomallei. Melioidosis is characterised by high mortality and morbidity and can involve the central nervous system (CNS). We have previously discovered that B. pseudomallei can infect the CNS via the olfactory and trigeminal nerves in mice. We have shown that the nerve path is dependent on mouse strain, with outbred mice showing resistance to olfactory nerve infection. Damage to the nasal epithelium by environmental factors is common, and we hypothesised that injury to the olfactory epithelium may increase the vulnerability of the olfactory nerve to microbial insult. We therefore investigated this, using outbred mice that were intranasally inoculated with B. pseudomallei, with or without methimazole-induced injury to the olfactory neuroepithelium. Methimazole-mediated injury resulted in increased B. pseudomallei invasion of the olfactory epithelium, and only in pre-injured animals were bacteria found in the olfactory nerve and bulb. In vitro assays demonstrated that B. pseudomallei readily infected glial cells isolated from the olfactory and trigeminal nerves (olfactory ensheathing cells and trigeminal Schwann cells, respectively). Bacteria were degraded by some cells but persisted in other cells, which led to the formation of multinucleated giant cells (MNGCs), with olfactory ensheathing cells less likely to form MNGCs than Schwann cells. Double Cap mutant bacteria, lacking the protein BimA, did not form MNGCs. These data suggest that injuries to the olfactory epithelium expose the primary olfactory nervous system to bacterial invasion, which can then result in CNS infection with potential pathogenic consequences for the glial cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antithyroid Agents / administration & dosage
  • Antithyroid Agents / pharmacology
  • Burkholderia pseudomallei*
  • Genes, Reporter
  • Giant Cells
  • Humans
  • Melioidosis / microbiology*
  • Melioidosis / pathology
  • Methimazole / administration & dosage
  • Methimazole / pharmacology
  • Mice
  • Mice, Transgenic
  • Olfactory Bulb / microbiology*
  • Olfactory Nerve / microbiology*
  • Respiratory Mucosa / injuries
  • Respiratory Mucosa / microbiology
  • S100 Calcium Binding Protein beta Subunit / genetics
  • S100 Calcium Binding Protein beta Subunit / metabolism*

Substances

  • Antithyroid Agents
  • S100 Calcium Binding Protein beta Subunit
  • S100B protein, human
  • Methimazole

Grants and funding

This study was supported by an Australian Research Council Discovery grant (DP150104495) to JE, KB and JSJ (https://www.arc.gov.au/grants/discovery-program/discovery-projects), a Clem Jones Foundation grant to JE and JS (https://experts.griffith.edu.au/project/ndf0b8caf8de786e2416acec7fc2c92b7), a Menzies Health Institute Queensland Capacity Grant to JE, AC and KB (https://www.griffith.edu.au/menzies-health-institute-queensland), a Goda Foundation grant to JE and JSJ, an Australian Government Research Training Program Scholarship to HW (https://www.education.gov.au/research-training-program), and a Griffith University International Postgraduate Research Scholarship to AD (https://www.griffith.edu.au/research-study/scholarships/guiprs). The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.