Lipopolysaccharide preconditioning prevents incision infection induced by drug-resistant bacteria in mice / 中华临床感染病杂志

ABSTRACT

Objective To investigate the effect of low dose lipopolysaccharide ( LPS ) preconditioning on prevention of incision infection by drug-resistant bacteria.Methods Methicillin-resistant Staphylococcus aureus ( MRSA) suspension with concentration of 1.8 ×109 CFU/mL was prepared.Sixty BALB/c mice were randomly divided into five groups (12 in each group, half male and half female).A medical longitudinal incision of the right thigh was made in mice in group 1-4, and 1, 0.5, 0.25 and 0 mL bacteria suspension was dropped on the surface of the incision and the incision was observed 4d after the model established.Group 5 was the blank control.Then 112 BALB/c mice were randomly divided into 7 groups ( each group had sixteen mice, half male and half female ) group A ( preconditioned with LPS 0.25 mg· kg-1· time-1), group B ( preconditioned with LPS 0.5 mg · kg-1 · time-1 ), group C (preconditioned with LPS 1 mg· kg-1 · time-1 ), group D (preconditioned with LPS 1.5 mg· kg-1 · time-1 ) , group E ( preconditioned with sterile normal saline) , group F ( incision infected) , and group G ( blank control) .LPS was given by intraperitoneal injection 48 h and 24 h before the establishing of the infection model.Body temperature was monitored every day after the model established, blood routine examination was performed on d3 and d7, and serum cytokines was detected on d7.All the mice were sacrificed on d7, and soft tissues around the incision were taken for hematoxylin-eosin staining.Repeated measures ANOVA and univariate ANOVA were performed for data analysis. Results Redness and suppuration were observed in 6 mice infected with 0.5 mL bacteria suspension, respectively, then 0.5 mL bacteria suspension was used for LPS preconditioning experiments.With LPS preconditioning, the body temperatures of mice in group B were with relatively minor changes, and the rises of white blood cells and lymphocytes on d3 and d7 were relatively modest.Granulocytes in group B returned to the normal level on d7.Besides, the rises of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-αin group B were also less, while IL-10 was increased greatly.Suppuration was observed in 4 mice in group B ( 4/16, 25.00%), and the rate was lower than group D, E and F (χ2 =7.988, 19.940 and 19.940,P<0.01). Conclusion LPS (0.5 mg· kg-1 · time-1 ) preconditioning can reduce the severity of incision infection caused by MRSA in mice.