Study on four circulating inflammatory parameters in animal model of systemic infection

Abstract

Objective To explore the possibility of using four circulating inflammatory parameters for the differential diagnosis of systemic gram-negative and gram-positive bacterial infections in mouse models.Methods Escherichia coli and Staphylococcus aureus were respectively inoculated into mice through tail vein to establish the animal models of systemic infection by representative gram-negative and gram-positive bacteria.Four parameters including the levels of white blood cell counts (WBC),C-reactive protein (CRP),procalcitonin (PCT) and interleukin 6 (IL-6) in blood samples were detected at 1,3,6,10,12 hours,as well as 2 and 5 days after bacteria inoculation.Results Levels of WBC in mice inoculated with Escherichia coli and Staphylococcus aureus were increased significantly at 10 hours after inoculation,which were (1.9 ± 0.52)×l09/L and (2.1±0.70) ×l09/L respectively.Levels of CRP [(258.1±13.4) ng/ml and (233.5±59.9) ng/ml] and PCT [(1824.6±331.4) pg/ml and (594.4±93) pg/ml] were all significantly up-regulated at 3 hours after inoculation.Levels of IL-6 were transiently increased in mice inoculated with Escherichia coli at the time point of 1 hours [(226±34.2) pg/ml],but were below detectable limit at any other time points as compared with those in control group and Staphylococcus aureus infected group.The ROC curves of four parameters indicated that only the areas under the curve (AUC) of IL-6 showed significant differences between two infections.Conclusion Levels of IL-6,CRP and PCT were significantly increased in early stage of bacterial infection.IL-6 level showed significant difference between Escherichia coli and Staphylococcus aureus infections. Key words: Infection ; White blood cell count ; C-reactive protein; Procalcitonin; Interleukin-6