Isolation and Identification of Actinobacillus pleuropneumoniae Serotype 1 from a Swine Farm in Fujian Province
[Objective]The aim of this experiment was to isolate and identify Actinobacillus pleuropneumoniae(APP)from the lungs of dead pigs suspected to have contracted contagious pleuropneumoniae from a pig farm in Fujian province,and to determine the serotype and biological characteristics of APP strain.In order to provide scientific basis for clinical rational drug use and epidemic prevention strategy in pig farms.[Method]In this study,the lung tissue of a suspected to have died from APP infection was isolated,cultured,stained and biochemical identified.PCR amplification of 16S rRNA and Apx Ⅳ toxin genes and serotype analysis were performed.Drug susceptibility test and animal pathogenicity test were used to investigate the drug resistance and virulence.[Result]A strain from diseased pig lung was successfully isolated.The isolate was round colonies with smooth,orderly,greyish-white translucent,Gram staining was negative with short bacilli with polymorphic,which had the culture characteristics of APP.Biochemical identification results showed that the isolate could use xylose,glucose and mannitol,urease,nitrate reduction and methyl red tests were positive,which was consistent with the biochemical characteristics of APP.The sequencing results of 16S rRNA and Apx Ⅳ genes showed that the similarity between the amplified sequence and the APP sequence in GenBank was more than 98％,which further confirmed that the isolate was APP and named it APP FJ2022.Serotype identification showed that the isolate was growth-dependent serotype 1 strain.The results of drug sensitivity test showed that the isolate was sensitive to cefotaxime,cefuroxime and cefmetazole,amoxicillin,and resistant to tetracycline,ampicillin,ciprofloxacin and flufenicol.The results of animal pathogenicity test showed that the isolate was pathogenic to mice,and its median lethal dose(LD50)was 7.71×108 CFU.[Conclusion]In this study,a serotype 1 APP strain was isolated from dead pig suspected to be infected with pleuropneumonia in a large-scale pig farm in Fujian province.The isolate was resistant to many common antibiotics and showed strong pathogenicity.The experimental results were helpful to understand the serotype of APP in Fujian province,and provide reference for the prevention and control of APP infection in pig farms.
万方数据
维普
