Objective: In the pathogenesis of Pseudomonas aeruginosa infections, cell to cell signal transmission system known as Quorum Sensing (QS), has an important role. Three interrelated QS systems are defined in P. aeruginosa namely las, rhl and quinolone. Experimental animal models are widely used in examining the effects of QS system. In this study, the effects of P. aeruginosa QS system on lung histopathology were assessed by two different rat infection model.

Materials and Methods: P. aeruginosa PAO1 (QS wild type) and PAO JP2 (QS mutant; ΔlasI/ΔrhlI ) reference laboratory strains were administered to Wistar albino rats, weighing 230-280 gr, by intranasal (n=21) and intraperitoneal (n=21) routes. Rats were executed after 24 hours and lung tissue samples of rats were investigated for capillary congestion, hemorrhage, infiltration of polymorphonuclear cells and alveolar septum thickening, in terms of damage scoring.

Results: Macroscopic and microscopic damages were observed 24 hours after the administration of bacteria. Lung damage observed in the PAO1 group was significantly higher than the control and PAO JP2 groups for both of the administration routes. PAO JP2 was determined to cause more pulmonary damage in the infection model induced by intranasal administration compared to the intraperitoneal administration.

Conclusion: Experimental lung infection model, induced by intranasal and intraperitoneal administration of bacteria, is a very simple method to apply. It would be useful in examining the effects of various virulence factors, as well as QS system. Although QS system has a significant role in the pathogenesis of the lung damage induced by the two application methods, damage caused by QS mutant strains suggests that different mechanisms that funtion in pathogenesis should be further addressed.