Abstract
Pseudomonas aeruginosa is a common gram-negative bacterium that usually causes nosocomial infection. The main pathogenicity of P. aeruginosa is caused by its virulence factors. PA2146 is reported to be a potential virulence-regulating gene and is highly expressed in the biofilms of P. aeruginosa. However, the effect of PA2146 mutant (PAO1ΔPA2146) on the macrophage immune response and murine models has not been reported. In the present study, PA2146 knockout was performed by homologous recombination. We found that PAO1ΔPA2146 stimulation significantly increased pyocyanin production but inhibited interleukin-6 secretion by neutrophils compared to PAO1 stimulation. In addition, PAO1ΔPA2146 treatment significantly inhibited cytokine production in macrophages independent of cell killing. In an acute pneumonia murine infection model, treatment with P. aeruginosa infected with PAO1ΔPA2146 inhibited cytokine secretion in the lungs but increased the infiltration of inflammatory cells compared to the wild-type group. The paradoxical results indicate that PA2146 deletion may also increase the production of virulence factors other than pyocyanin, which may not only increase inflammatory cell infiltration in the lungs but also lead to immune cells "shock." Overall, our findings suggest that PA2146 could serve as a P. aeruginosa virulence-regulating gene that regulates its macrophage and host immune response.