| The infections disease caused by bacterial is a serious threat to human health,since the application of antibiotics, the disease greatly improved. However, with the widespread use of antibiotics, resistance-bacterial is increasing. In the region, infectious diseases are more vulnerable to happen; the rates of lower respiratory tract infections and mortality are very high. According to U.S. research, the death of the last 50 years did not decreas,even increase slightly because pulmonary infection,. The reasons of public Health Medicine for future infectious disease may go deep into find their potential biological knowledge. Animal infection model and In vitro are two important means to study the mechanism human pulmonary. Animal infection model is considered to be an the basic tools of the study with human disease, development and evaluation of drug efficacy. Animal models are widely used to study pharmacodynamics. Current the main way of pulmonary infection animals are:1) Directly exposuring to infected:Spread of pathogens exhaled by the animal susceptible to infection or physical contact of gas means to make the infection of uninfected animals to achieve the purpose of vaccination.2) Atomization:by exposing the nose or body in a close spray place, inhaling amount of aerosol particles of microbial to infect.3) Intubation by the way of bronchial or oral to make the inoculation into the lower respiratory tract::By the way of oral intubation or tracheal instillation to make the inoculum directly into the lower respiratory tract animals.4). Nasal:the capacity of Inoculum about 5-50ul,less would result in suspension of sediment in the upper respiratory tract.For the past few years, to control the nosocomial infection caused by multidrug resistant gram-negative bacteria is always an important issue in the field of medicine. Although many new antibiotics had come out and been used extensively,which effectively decreased the rate of nosocomial Enterobacteriaceae, but the increasing of number of non-fermentative bacteria such as Pseudomonas aeruginosa, Acinetobacter baumannii isolated in clinical practice actually.Acinetobacter baumannii is an opportunistis pathogen, it is found in many health care environments, soil and water.the isolation rate of Acinetobacter baumannii is increasing year by year and the second highest just lower than that Pseudomonas aeruginosa in the non-fermentative bacteria Acinetobacter baumannii.has become an important opportunistis pathogen of nosocomial infections.The genus Acinetobacter consist of at least 32 described genomic species, seven of which have been named:①Acinetobacter baumannii (A.banmannii, gene species 2);②calcium acetate Acinetobacter (A. calcoacelicus, gene species 1);③hemolytic Acinetobacter (A.haemolyticus, gene species 4);④Johnson Acinetobacter (Ajohnonii, gene species 7);⑤Lafite Acinetobacter (A.lwoffii, gene species 4);⑥Joan baumannii (A.junii, gene species 5);⑦Radiation-resistant Acinetobacter (A.radioresistens, gene species 12). Of Acinetobacter genus Acinetobacter calcoaceticus, A. baumannii, Acinetobacter genomic species 3 and Acinetobacter genomic species 13sensuTjemberg And Ursing Means that they are indistinguishable in most routine clinical diagnostic laboratories, where they are grouped together as the A. calcoaceticus-A. baumannii(Ac-Ab)complex. In recent years, Acinetobacter baumannii is emerging as a cause of numerous global outbreak, displaying ever-increasing rates of resistance year by year. There are reported multi-resistant drug or pan-resistant Acinetobacter baumannii outbreak around the world such as Europe, North America, China, China Taiwan, etc. The mechanisms underlying resistance to drug in A. baumannii are still poorly understood, but they would be expected to be similar to those described in other Gram-negative bacteria:1), resulting in inactivation of enzymes and passive activity (includingβ-lactamase and aminoglycoside modifying enzymes); 2) alterations in cell outer membrane and Penicillin-binding protein (PBPs); 3)decreased outer membrane permeability caused by the loss or reduced;4)expression of porins? overexpression of multidrug effiux pumps, reducing intracellular antibiotic concentration in the bacteria.The treatment of Acinetobacter baumannii is difficulty in clinical actually, Animal models of A. baumannii pneumonia is lack currently, especially animal models of pneumonia caused by multi-drug resistant Acinetobacter baumannii has rarely been reported, The consequence In vitro susceptibility testing and results with the clinical use of drugs are not totally consistent, and even contradictory.Therefore, In this study, using cyclophosphamide and glucocorticoid make rats model of immunosuppression with neutropenia,and then and then innculated Acinetobacter baumannii (intratracheal) to establish pneumonia model. A. baumannii pneumonia model has been successfully established in rats with leucopenia, for clinical treatment of Acinetobacter baumannii provide the basis tools. All statistical analysis was carried out by SPSS 13.0 and origin.The first section of this research:Comparison of immunosuppression induced by different doses of cyclophosphamide in normal rats BackgroundRecent years,With the development of medical technology,increasing rates of caner,,autoimmune and other immune-related diseases to improve diagnosis and organ transplantation, the trouble is also facing a growing number of immunosuppressive patients with Leukopenia treatment in clinical with the plight of infected individuals. Animal infection model is considered to be an the basic tools of the study with human disease, development and evaluation of drug efficacy. Animal models are widely used to study pharmacodynamics. Research animals at home and abroad are mostly applied in mice, rare use of rats. This study aims to provide a basis for clinical research.ObjectiveIn order to Simulationthe clinical immunocompromised patients, we evaluate the combination of cyclophosphamide and dexamethasone in rats on immune function of Sprague Dawleg. Explore different doses of cyclophosphamide and dexamethasone on rat immune suppression and to find the best concentration.Methods50 SPF Sprague Dawleg rats were randomly divided into five groups,Intermittent intraperitoneal injection to Sprague Dawleg rats were injected with different doses of cyclophosphamide and intramuscular injection of dexamethasone (group A were each cyclophosphamide 30mg/kg, dexamethasone 60mg/kg, a total of two, the same below. B group cyclophosphamide 45mg/kg, dexamethasone 90mg/kg, C group cyclophosphamide 60mg/kg, dexamethasone 120mg/kg, D group cyclophosphamide 75mg/kg,150mg/kg dexamethasone), observed time of peripheral blood white blood cell count, activity, and mortality were observed.ResultsDose changes in white blood cells are reduced over time, after all the medication for at least forty-five days after the cells, maintained at a low level, white blood cells after the gradual recovery of body weight showed a decreasing trend, peripheral white blood cells:Group A of immune effect of lighter, faster recovery and sustained time is short, C, D cells decreased rapidly, but the mortality rate higher, Group B cells decreased and mortality were better in the normal control group in weight, white blood cell count, activity around the area did not change significantly.ConclusionBy the way of cyclophosphamide combined effect of dexamethasone,B (cyclophosphamide 90mg/kg dexamethasone 180mg/kg) dose, mortality rate in rats at least, the immune best for the establishment of this dose immune suppression model.The second section of this research:Establishment of Acinetobacter baumannii pneumonia Model in Rats with LeukopeniaObjectiveIn the immunocompromised state,we establish Acinetobacter baumannii pneumonia model in rats with leucopenia. establish Acinetobacter baumannii pneumonia model in rats with leucopenia.Methods45 Sprague-Dawleg rats were randomized into 3 groups:control group, immunosuppressive group and the model group (n=15). The cyclophosphamide (45 mg/kg, intraperitoneal) and dexamethasone (90 mg/kg, intramuscular) were used 4d and 1d before Acinetobacter baumannii inoculation in order to reduce the WBC counts in blood, and then innculated MDR Acinetobacter baumannii (1.2×109CFU/ml, intratracheal) to establish pneumonia model. Immunosuppression group and control group were similar to the dose of intratracheal instillation of sterile saline.The activity, drinking and eating of the animals were observed dynamically. And the wet to dry ratio of weight of lung tissue. bacteriology and lung pathological change were monitored and compared among groups. Reference Chen TL, Acinetobacter baumannii primer:primerl:ITSF (5(?)-CATTATCAC GGTAATTAGTG), ITSB (5(?)-AG AGCACTGTGCACTTAAG), amplified genes in the interval region of 16sRNA, fragment about 208 bp; primer2:rAl (5(?)-CCTGAATCTTCTGGTAAA AC), rA2 (5(?)-GTTTCTGGGCTGCCAAACATTAC), amplified the highly conserved sequence, fragment about425 bp. The primers were synthesized by Shanghai invitrogen company. Statistical data were expressed as mean±standard deviation (x±s), count comparative analysis of repeated measures data.ResultsThe activity, drinking and eating of the animals were increased 6h after infusion of A. baumannii. Comparison to the control group, Leukopenia group and model group than in the wet to dry after inoculation. (P＜0.05), Leukopenia group 7d after inoculation of bacteria than the wet to dry to normal, but the model group were significantly higher than normal, there was significant difference between the groups (P<0.05). Bacteriological examination:bacteria culture are grown in model of lung tissue after injection of bacteria in each time,and identified Acinetobacter baumannii by PCR. The pneumonia pathological change, such as neutrophil infiltration, alveolar hemorrhage appeared 6h after A. baumannii inoculation and it stared to recover after 36h in the model group while light pneumonia change occurred and recovered soon after that in the other groups.ConclusionA. baumannii pneumonia model has been successfully established in rats with leucopenia by Intratracheal instillation method.. |
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