Study On Different Genotype Of Acinetobacter Baumannii And The Pathogenicity

Objectives:1. To establish the pneumonia model caused by acinetobacter baumannii in mice.2. To study the pathogenic differences of3different genotypes of acinetobacter baumannii strains.Methods:1046-week-old male BALB/C mice were randomly selected and randomly divided into4groups. The mice rendered transiently neutropenic by intraperitoneal injection with150mg of cyclophosphamide per kg of body weight on the1and2days. three groups were respectively given intratracheal instillation of different bacteria suspension50μl (1McFarland concentration) to induce acinetobacter baumannii pneumonia,; corresponding to a concentration of3×108colony forming units (CFU)/ml, physiological saline was used instead of acinetobacter baumannii suspension in control group.10mice in each group were raised until the end of the experiment. Fatality and weight changes were observed every day for clinical scoring. Alternating in each group3mice take blood line of white blood cell detection.Among the rest15mice in each group,3mouse in each group was executed at1h after vaccination. Their lung homogenates were given bacterial culture and counts. After that,3mice in each group were took blood specimens for detection of inflammatory factors (IL-1β、IL-6、 TNF-a)and PCT;3mice in each group were executed daily and their lung homogenates were also given bacterial culture and counts, and the pathological sections of the lung tissues were given histological grading.Results:l.Mice of the three groups given different acinetobacter baumannii suspensions all had different levels of depression, decreased activity, poor diet, raised fur, conjunctival congestion, and weight loss.Mortality is not the same in each group. Four days after the symptoms disappeared, the mice were returned to normal diet. Mortality of the three groups of pneumonia changed from20%to90%. In the control group, the mice had good spirit, appetite, normal fur and good response, and no obvious signs of illness or mortality.2.Difference of clinical scores among groups was statistically significant (P<0.05). Three groups of bacterial pneumonia, ST191clinical score the highest, STN2center, ST381is the lowest. But there is no significant white blood cell count, body weight loss difference between groups (P>0.05)3.Inoculation of different strains, the bacterial colony count was obviously different in lung homogenate culture in the first day (P<0.05). the STN2group bacteria number is largest.Pathology scores between the groups had statistically significant difference (P<0.05). Three groups of bacterial pneumonia lung pathology score was significantly higher than the control group, three groups of bacterial pneumonia ST191pathological score highest, STN2center, ST381minimum.Inflammation factors (IL-1β、IL-6、TNF-α)、PCT and histological scores were different in mice with different strains (P<0.05). ST191group of pro inflammatory cytokines and PCT levels higher than the other three groups.4. survival was closely correlated with clinical scores,Score of lung tissue pathology, TNF-a and PCT (respectively (rs=-0.866,rs=-0.826, rs=-0.629,rs=-0.685)), but fatality had nothing to do with the bacterial count of lung tissue homogenate.Conclusions:1. Pneumonia model in mice is successfully established with cyclophosphamide to suppress the immunoreaction, and with endotracheal instillation of acinetobacter baumannii suspension.2. Statistical analysis on differences of survival, Inflammation cytokines, clinical scores and histopathological scores of different genotypes of acinetobacter baumannii pneumonia model in mice shows that there are differences of the pathogenicity between different strains. Epidemic strain ST191has the highest fatality, In the region of bacterial pneumonia in hospital infection control and the world hydrocarbon mildew-resistant Acinetobacter baumannii ene virulence studies provide useful information.3. Correlation analysis finds that in the proliferation of the bacteria is not the main pathogenic factor for acinetobacter baumannii pneumonia. And clinical scores, inflammatory factors, Pathology scores and PCT are closely related to the mortality.