Molecular Biological Identification And Pathogenicity Of Acinetobacter From Pigs

In order to study the species and pathogenicity of 30 strains of Acinetobacter spp.isolated and identified from pig lung tissue in 2019,molecular biological identification method was used to identify 30 strains of Acinetobacter spp.,and different species of Acinetobacter spp.were selected for the pathogenicity test in mice,so as to provide basis for the strain identification and pathogenicity research of Acinetobacter spp.from pigs.Firstly,the bla OXA-51-like genes were amplified to identify Acinetobacter baumannii,and then the rpo B Zone1,rpo B zone2 and gyr B genes were amplified respectively for sequencing analysis to identify non Acinetobacter baumannii strains.The final identification result was that the results of two or three identification methods were consistent.The results showed that,among the 30 strains of Acinetobacter spp.,2(6.67%)were identified as Acinetobacter baumannii and 28(93.3%)as non-Acinetobacter baumannii.Among the non-Acinetobacter baumannii strains,6(21.4%)were identified as A.lwofii,12(42.9%)as A.townseri,5(17.9%)as A.junii,and 3(10.7%)as A.ursingii.Two strains were identified by only one method,but no strains were identified.Only 28(93.3%)of the 30 Acinetobacter spp.strains were identified.Two strains of Acinetobacter baumannii and four strains of A.lwofii,A.townseri,A.junii and A.ursingii were injected intraperitoneally into mice(0.3 m L/mouse).The bacterial concentration of each strain in experimental groups were 1.0×105,1.0×106,1.0×107,1.0×108,1.0×109 CFU/m L,and a group of normal saline control group.The median lethal dose(LD50)was determined.The clinical manifestations and histopathological examination were observed.The results showed that,the LD50 of two Acinetobacter baumannii strains were 1.20×107 CFU/m L and 1.26×107 CFU/m L respectively,the dead mice were found to have congestion and swelling of the lung.The mice in the high concentration group of non-Acinetobacter baumannii had only clinical manifestations,but did not die.The mice were killed and dissected,and their lungs were occasionally found to have bleeding points and swelling.There were no obvious abnormality in liver,spleen and kidney of Acinetobacter baumannii and non-Acinetobacter baumannii experimental groups.Histopathological observation showed that there were inflammatory cell infiltration and hyperemia in the lung and liver of mice killed by Acinetobacter baumannii,and a small amount of inflammatory cell infiltration in the lung and liver of mice with non Acinetobacter baumannii disease.Pathological observation of spleen and kidney of Acinetobacter baumannii test group and non-Acinetobacter baumannii test group was not abnormal.Conclusion: two strains of Acinetobacter baumannii and 28 strains of non Acinetobacter baumannii were identified,among which 6 strains were A.lwofii,12 strains were A.townseri,5 strains were A.junii and 3 strains were A.ursingii.High concentration of Acinetobacter baumannii can kill mice,while high concentration of non Acinetobacter baumannii can only infect mice but not lethal.