Open Biology (Jan 2016)

The distinct fate of smooth and rough Mycobacterium abscessus variants inside macrophages

  • Anne-Laure Roux,
  • Albertus Viljoen,
  • Aïcha Bah,
  • Roxane Simeone,
  • Audrey Bernut,
  • Laura Laencina,
  • Therese Deramaudt,
  • Martin Rottman,
  • Jean-Louis Gaillard,
  • Laleh Majlessi,
  • Roland Brosch,
  • Fabienne Girard-Misguich,
  • Isabelle Vergne,
  • Chantal de Chastellier,
  • Laurent Kremer,
  • Jean-Louis Herrmann

DOI
https://doi.org/10.1098/rsob.160185
Journal volume & issue
Vol. 6, no. 11

Abstract

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Mycobacterium abscessus is a pathogenic, rapidly growing mycobacterium responsible for pulmonary and cutaneous infections in immunocompetent patients and in patients with Mendelian disorders, such as cystic fibrosis (CF). Mycobacterium abscessus is known to transition from a smooth (S) morphotype with cell surface-associated glycopeptidolipids (GPL) to a rough (R) morphotype lacking GPL. Herein, we show that M. abscessus S and R variants are able to grow inside macrophages and are present in morphologically distinct phagosomes. The S forms are found mostly as single bacteria within phagosomes characterized by a tightly apposed phagosomal membrane and the presence of an electron translucent zone (ETZ) surrounding the bacilli. By contrast, infection with the R form leads to phagosomes often containing more than two bacilli, surrounded by a loose phagosomal membrane and lacking the ETZ. In contrast to the R variant, the S variant is capable of restricting intraphagosomal acidification and induces less apoptosis and autophagy. Importantly, the membrane of phagosomes enclosing the S forms showed signs of alteration, such as breaks or partial degradation. Although not frequently encountered, these events suggest that the S form is capable of provoking phagosome–cytosol communication. In conclusion, M. abscessus S exhibits traits inside macrophages that are reminiscent of slow-growing mycobacterial species.

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