Isolation, Identification And Immunoprophylaxis Of Actinobacillus Pleuropneumoniae

A Gram-negative coccobailli bacterium was isolated from seious hemorrhagic lungs, liver, spleen and effusion in thoracic cavity of the dead piglets. The cells were 0.7~1.6x0.2~0.5um, arranged singly, in pairs, in short chains or in lamps. The isolated didn't grow on common nutrition agar, common broth or macconkey nutrition agar. Colonies on sheep blood agar growing 18 to 24h, were opaque, coesius, moist, smooth, raised and completely hemolytic. Hemorrhagic band around staphylococcus aureus became wide obviously in CAMP test. Acid but no gas was produced from carbohydrates, lactose, xylose or glocitol was unutilized, also the isolasted growing needed NAD.It was positive for urease and changing nitrates into nitrites, and negative for catalase, oxidase, VP and MR. No indole or H2S was produced. Culture of the isolate were liable to death at 4℃. Heavy suspensions of cultures may be preserved for a longer time by lyophilization in skim milk at -40℃. The isolated was a high virulence strain. The broth culture of the isolated (3xl08~4xl09) could lead the mice to death.It was also pathogenic to guinea pigs. The broth culture could lead piglets to death or pathogeny at different degree by different inoculation path. Piglets by intrathoracis inoculation was the most fast to pathogenesis, and the symptom was more typical.Attacked piglets caught, sneezed and anhelted difficultly, which became serious attacked by other bacterium, and some of them staggered. There was large effusion in thoracic cavity. Pericardium became thick adhering to lung or pleura. Lungatrophiaed with canous or vinous necroticlession or petechia on surface, and spumose fluid flowed from bronchi insection. Liver and kidney bossed with necrotic lesion on surface and tumica turgored. Mucous layer swelled on endotrachea. No lession appeared in systema digestorium. Not too much slurry was found in alveolar. Iterstitium necrosised and pulmonary vein dilald and hypermiaed.Infecting bacteria was isolated from Lession tissue of dead piglets. From the studies of the bio-characteristics and zoopery, It was concluded that the isolated bacterium in shaanxi \vas Actinobacillus pleuropnumoicae.The isolated was not sensitive to a wide range of commonly-used antimicrobial angents. Swines and piglets immuned with inactivated vaccine were protected at different degree. Antibody was up to over 27. Unimmuned not immuned piglets attacked in infectious test.