Abstract: Goose pasteurellosis， caused by the bacterium Pasteurella multocida（Pm）， was a major infectious disease of goose in China in recent years. To identify the pathogen of goose disease in a goosebreeding farm， the causes of epidemic situation were investigated. A gramnegative bacillus was isolated and purified from the livers and hearts samples of the sick geese that preliminary diagnosed as pasteurellosis based on clinical symptoms and pathological changes， and it was identified as goose Pasteurella multocida by morphological and cultured characteristics， biochemical tests， animal pathogenic tests， drug sensitivity tests， species and serotype PCRs and so on. Then its serotype associated genes for serotype PCRs were cloned and analysed. The results showed that the goose Pm isolate had typical morphology and biochemical characteristics of P. multocida subsp. multocida， and it belonged to capsular type A and serotype Ⅰ. This Pm isolate had a strong pathogenicity， and its minimus lethal dose （MLD） to mice was 5 cfu. Drug sensitivity tests showed that this isolate was only sensitive to cefatrizine， cefalotin， ceftazidime， ceftizoxime and florfenicol. A capsular biosynthesis associated gene hyaDhyaC about 4 155 bp in this isolated Pm strain was amplified and sequenced， which shared a 99% homology with the published gene sequences. The serotype Ⅰ PCR target gene fragments about 303 bp of this goose Pm strain and the reference strain C481 were purified and sequenced， the sequencing results were exactly the same. All these results indicated that the goose Pm isolate which had a strong pathogenic and belonged to capsular type A and serotype Ⅰ， was the pathogen of goose disease to be diagnosed. And the amplified hyaDhyaC gene sequences and serotype Ⅰ PCR target gene fragments of this Pm isolate both exhibited relative stability.

Key words: goose, Pasteurella multocida, serotype, PCR