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Sci Rep. 2017 May 18;7(1):2120. doi: 10.1038/s41598-017-02349-0.

Pseudomonas aeruginosa Exolysin promotes bacterial growth in lungs, alveolar damage and bacterial dissemination.

Bouillot S1,2,3,4, Munro P5,6, Gallet B1,7,8, Reboud E1,2,3,4, Cretin F1,2,3,4, Golovkine G1,2,3,4, Schoehn G1,7,8, Attrée I1,2,3,4, Lemichez E5,6, Huber P9,10,11,12.

Author information

1
Université Grenoble Alpes, F-38000, Grenoble, France.
2
CNRS, ERL5261, F-38000, Grenoble, France.
3
CEA, BIG-BCI, F-38000, Grenoble, France.
4
INSERM, U1036, F-38000, Grenoble, France.
5
INSERM, U1065, F-06204, Grenoble, France.
6
Université de Nice-Sophia-Antipolis, F-06204, Grenoble, France.
7
CEA, IBS, F-38000, Grenoble, France.
8
CNRS, UMR5075, F-38000, Grenoble, France.
9
Université Grenoble Alpes, F-38000, Grenoble, France. phuber@cea.fr.
10
CNRS, ERL5261, F-38000, Grenoble, France. phuber@cea.fr.
11
CEA, BIG-BCI, F-38000, Grenoble, France. phuber@cea.fr.
12
INSERM, U1036, F-38000, Grenoble, France. phuber@cea.fr.

Abstract

Exolysin (ExlA) is a recently-identified pore-forming toxin secreted by a subset of Pseudomonas aeruginosa strains identified worldwide and devoid of Type III secretion system (T3SS), a major virulence factor. Here, we characterized at the ultrastructural level the lesions caused by an ExlA-secreting strain, CLJ1, in mouse infected lungs. CLJ1 induced necrotic lesions in pneumocytes and endothelial cells, resulting in alveolo-vascular barrier breakdown. Ectopic expression of ExlA in an exlA-negative strain induced similar tissue injuries. In addition, ExlA conferred on bacteria the capacity to proliferate in lungs and to disseminate in secondary organs, similar to bacteria possessing a functional T3SS. CLJ1 did not promote a strong neutrophil infiltration in the alveoli, owing to the weak pro-inflammatory cytokine reaction engendered by the strain. However, CLJ1 was rapidly eliminated from the blood in a bacteremia model, suggesting that it can be promptly phagocytosed by immune cells. Together, our study ascribes to ExlA-secreting bacteria the capacity to proliferate in the lung and to damage pulmonary tissues, thereby promoting metastatic infections, in absence of substantial immune response exacerbation.

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