| Objective The lung infection model of Acinetobacter baumannii in immunosuppressive mice was established,and the changes of inflammatory indexes and lung histopathology in different infection stages of the model mice were analyzed.The expression characteristics of outer membrane protein W(OmpW)of Acinetobacter baumannii in lung tissues of infected mice were further detected.To explore the possible role of OmpW in mouse pneumonia caused by Acinetobacter baumannii and to provide experimental basis for further clarifying the infection mechanism of Acinetobacter baumannii and research and development of new anti-infective drugs.Methods Balb/c mice were randomly divided into experimental group(high concentration group and low concentration group)and control group with 15 mice in each group.All mice were immunosuppressed by intraperitoneal injection of cyclophosphamide(3mg/d for 2days).The experimental group was inoculated with different concentrations of Acinetobacter baumannii solution by aerosol inhalation,while the control group was not inoculated with solution.The inoculation concentration of high concentration group was 1× 10? CFU/m L,and that of low concentration group was 1×10? CFU/m L.At 0h,24 h,48h,72 h and 96 h after inoculation,3 mice in each group were taken to dynamically observe the status,body weight,the characteristics of inflammatory changes in lung tissue,blood cell level,bacterial colony count in BAL Fluid,and the changes of IL-6 and TNF-? level in peripheral blood.At the same time,quantitative real-time PCR was used to detect the changes of OmpW m RNA expression in the lung tissue of mice in the experimental group with the process of infection.Results 1.Model mouse state: After infected with Acinetobacter baumannii,the state of mice in the experimental group became worse and their body weight lost.The state of mice and the body weight in the high concentration group was worse,and one mouse in the high concentration group died in 24 h.2.Morphological changes and histopathological characteristics of lung tissue in model mice: The histopathological results showed that the pulmonary inflammation in the experimental group was more apparent than that in the control group.The exudation of inflammatory cells and pulmonary interstitial congestion could be seen in the experimental group.It can be seen that the pulmonary inflammation in the high concentration group was more serious than that in the low concentration group.3.Inflammation index of model mice: the peripheral blood leukocyte and neutrophil count of mice in the experimental group began to increase at 24 h after infection,and increased progressively with the process of infection,and the high concentration group was significantly higher than the low concentration group.At different time points,the leukocyte and neutrophil counts in the high and low concentration groups were significantly higher than those in the control group.4.Bacteriological characteristics of model mice: the colony count of BAL Fluid and lung tissue of mice in the experimental group reached the peak at 0h and 24 h respectively,and then decreased gradually.At 0h after infection,the colony count of Acinetobacter baumannii in high and low concentration groups was >1×10? CFU/m L,which was significantly higher than that in the control group.At 24 h after infection,only the colony count of Acinetobacter baumannii in the high concentration group was more than 1×10? CFU/m L,which was statistically significant compared with the control group in the same period(0h:F=128.625,P=0.000;24h:F=55.5,P=0.000).5.Changes in the level of cytokines: compared with the control group,the level of serum IL-6 in the experimental group increased at 24 h after infection and remained at a certain level.TNF-? increased from 24 h to 48 h after infection.After that,the level of TNF-? in high concentration group continued to increase,while that in low concentration group decreased at 72 h.In the range of monitoring time,the levels of IL-6 and TNF-? in low concentration group were higher than those in high concentration group.6.Expression characteristics of OmpW m RNA in lung tissue of model mice: OmpW m RNA expression could be detected in lung tissue of mice in experimental group at different time of infection.At 24 h after infection,the expression level of OmpW m RNA in lung tissue of low concentration group was significantly higher than that of high concentration group(2.09/1.11,F=1105.719,P=0.000;2.37/1.15,F=515.548,P=0.000).With the extension of time,the expression of OmpW m RNA decreased in the low concentration group and increased in the high concentration group.Conclusion 1.The mice model of pulmonary infection induced by different concentrations of Acinetobacter baumannii can be established by ultrasonic atomization.Inflammatory changes can be seen in the appearance and pathology of lung tissue in model mice.2.The inflammation degree of peripheral blood and lung tissue of model mice was positively correlated with the initial inoculation concentration of Acinetobacter baumannii.The higher the concentration of Acinetobacter baumannii,the more obvious the inflammatory changes of lung tissue,accompanied by the increase of peripheral blood leukocytes and neutrophils.3.The concentrations of IL-6 and TNF-? in the peripheral blood of mice in the experimental group increased with the progress of infection,but the concentrations of IL-6 and TNF-? in the peripheral blood of mice in the low concentration group were higher than those in the high concentration group at the same time.4.OmpW m RNA was expressed in the lung tissue of all concentration groups,and its change trend was consistent with the concentration of cytokine IL-6 or TNF-? in peripheral blood.The level of OmpW expression may be used as a new index to judge the process of pulmonary infection and the level of immune response of Acinetobacter baumannii,and may be used as a new drug target for the treatment of multi-drug-resistant or pan-drug-resistant Acinetobacter baumannii infection. |
PDF Full Text Request