The influence of Pseudomonas aeruginosa biofilm suspension and alginate on macrophage phagocytosis function in mouse

Objective To explore the influence of Pseudomonas aeruginosa(PA) biofilm and alginate on macrophage phagocytosis function in mouse.Methods The bacterial biofilm suspension of PA was used to infect macrophage-depleted mouse and control mouse to explore the influence of biofilm on macrophage.The macrophage was isolated from mouse and added with alginate inside,then the phagocytosis rate was determined.The capability of macrophage's phagocytosis was detected by neutral red method.Results The bacterial count in macrophage-depleted mouse compared to the control group was(4.16±3.36)×105 /ml to(5.15±1.92)×105 /ml,t=0.7211,P=0.483.The phagocytosis rate in PA biofilm group compared to the control group was(13.82±4.71)% to(42.73±11.00)%,Q=12.3231,P0.01.This suggested that the PA biofilm group can be more resistant to macrophage phagocytosis compared to the control group.The phagocytosis rate in alginate group compared to the control group was(22.91±6.20)% to(42.73±11.00)%,Q=8.4465,P0.05.This showed that the alginate group can also be more resistant to macrophage phagocytosis compared to the control group.When the concentration of alginate were 0,25,50,75,100,125 and 150 μg/ml the absorbance A(540 nm)which represents the capability of macrophage phagocytosing neutral red,were(0.271±0.044),(0.456±0.062),(0.445±0.061),(0.551±0.065),(0.210±0.053),(0.186±0.026)and(0.195±0.025)respectively.When the alginate's concentration ≤75 μg/ml,the capability of macrophage phagocytosing neutral red strengthened(P0.05),compared to the 0 μg/ml group;When the alginate's concentration 75 μg/ml,the capability of macrophage phagocytosing neutral red decreased(P0.05),compared to the 0 μg/ml group.Conclusion Macrophage can prevent the invasion of PA.PA biofilm can inhibit macrophage phagocytosis.Alginate can promote macrophage phagocytosis at doses of ≤75 μg/ml while larger doses of alginate inhibit macrophage phagocytosis.