[Objective] The paper was to explore the cause of disease with symptoms of swelling joint, blanc-loose stool and few deaths, so as to provide suggestions and effective measures for diagnosis and control of the disease in chicken farm. [Method] The diseased chick samples were collected for bacteriological examination. Through bacterial isolation culture, PCR identification, biochemical test and animal test, 5 strains of S. pullorum were identified. [Result] When the isolates were inoculated into SPF chicks, the same disease cases with natural infection could be reproduced. [Conclusion] S. pullorum is the major cause of the disease in chicken farm.
[Objective] The study aimed to obtain attenuated strain of Haemophilus parasuis.[Method] Tn5 transposon technology was used to construct a library of mutants.Positive mutants were screened by kanamycin resistance.False positive was identified by PCR and then removed.Mice were infected to detect the virulence of mutants.The bionomics of attenuated strains were detected,too.[Result] The attenuated mutants showed similar reproductive activity to that of wild strain.The virulence of mutants was still stable after 30 passages.[Conclusion] This study provided foundation for exploring the virulence factors and pathogenic mechanism of HPS.
