The In Vitro and In Vivo Effects of Pseudomonas aeruginosa DesB on Pathogen-host Interaction

Introduction: Pseudomonas aeruginosa is an important food spoilage psychrotropic bacterium, which is widely found in environments such as soil, plants, and animal tissues. It produces many virulence factors that contribute to spoilage in foods and host defense/activation of inflammatory responses/host damage in human. Notably, this spoilage pathogen can cause harmful chronic lung damage in immunocompromised patients. Previous study showed that an aerobic desaturase (DesB) of P. aeruginosa exerted significant effect on virulence determinants.

Purpose: The objectives of this study was to analyze the in vitro and in vivo effect of DesB on host interaction and possibly to expand the comprehension of its pathogenic effect on food hosts, such as mice.

Methods: For the in vitro experiments, P. aeruginosa (WT) or a desB mutant was grown up. The bacterial cells and supernatants were collected by centrifugation and, then, diluted with F-12 supplemented with 10% FBS. The diluents were added to A549 cell monolayer for determining cell viability, invasion, and/or immune response. For the in vivo experiments, six to seven weeks old ICR mice were infected by endotracheal intubation with six to seven log CFU/ml bacterial cell for 24 h. After the mice were sacrificed, the survival rates of each strain, in the lungs, were measured. The histopathology of lung tissue was, also, observed.

Results: The desB mutant exhibited lower cytotoxicity to A549 cells than WT and stimulated secretion of a more pro-inflammatory cytokine (IL-6) and chemokines (GRO, IL-8, and MCP-1) compared to WT. In mouse model, the survival rate of the desB mutant was lower than for WT in the lungs.

Significance: The results suggested that P. aeruginosa DesB affects pathogenicity and microbe-host interactions.