Analysis of the virulence of Pseudomonas aeruginosa

5 de May de 2020

P. aeruginosa is a bacterium that produces several life-threatening infections, especially in immunosuppressed patients, with cancer, burns, and cystic fibrosis, and is also one of the main causes of nosocomial infections. Coupled with the intrinsic resistance of this bacterium that makes it one of the most feared human pathogens, is its metabolic versatility and that it harbors multiple virulence factors that allow this pathogen to infect essentially any mammalian tissue. A central element of the infectious process is the pathogen's ability to adapt to changing environments and this bacterium produces many global regulators and signal transduction systems that facilitate its adaptation, as is the case of the sigma factor σVreI that promotes the transcription of potential determinants of virulence, including toxin secretion systems.

In a study published in the journal Scientific Reports entitled “The extracytoplasmic function sigma factor σVreI is active during infection and contributes to phosphate starvation-induced virulence of Pseudomonas aeruginosa”, in which Dr. Alain Ocampo from the Epidemiology and Mechanisms group has participated Pathogenic and Molecular Diseases of Infectious Diseases and Clinical Microbiology of IDIVAL, together with researchers from the Zaidín Experimental Station belonging to the Higher Council for Scientific Research of Granada and the Department of Medical Microbiology and Infection Control of the University of Amsterdam in the Netherlands, studied the role of the sigma factor σVreI during P. aeruginosa infection in phosphate-limiting media, a condition often encountered by pathogens in the host environment and known to induce a virulent phenotype in this bacterium. 

Until now it has not been studied whether σVreI was active in vivo during infection and whether it contributed to virulence induced by the lack of phosphate. Zebrafish embryo models and a human respiratory epithelial cell line were used as hosts for P. aeruginosa for this study. Through transcriptomic analysis, we show that VreR modulates gene expression, not only dependent on σVreI but also independently of σVreI. The importance of this work lies in the fact that it has been shown for the first time that σVreI is activated during infection and that the lack of σVreI / VreR signaling proteins decrease the virulence of P. aeruginosa induced by phosphate deficiency in the medium. This study has revealed new clues about the pathogenicity of P. aeruginosa in conditions similar to those that could occur in possible infections during major surgical operations and also in patients with severe burns, where the reabsorption of phosphate by the kidneys is reduced and losses exudatives are higher than normal, leading to hypophosphatemia or during respiratory alkalosis caused by sepsis or mechanical respiration, where a phosphate redistribution occurs in the cells, reducing their content and extracellular.

Ref. The extracytoplasmic function sigma factor σVreI is active during infection and contributes to phosphate starvation-induced virulence of Pseudomonas aeruginosa. Otero-Asman JR, Quesada JM, Jim KK, Ocampo-Sosa A, Civantos C, Bitter W, Llamas MA. Sci Rep. 2020 Feb 21;10(1):3139. doi: 10.1038/s41598-020-60197-x.