Mannheimia 属菌の野外実態と同定法の確立

Mannheimia spp. strains were identified by their 16S rRNA gene sequences. Among 133 isolates 76.7% (102 isolates) were M．haemolytica . On the other hand，96.0% serologically typeable strains were identified as M．haemolytica by their 16S rRNA gene sequences． The nucleotide sequences of the amplified gyrB DNA were determined directly from the amplified fragments． The base substitution frequency of gyrB between the strains of Mannheimia spp．was much higher than that of the 16S rRNA gene． With a specific set of PCR primers，it was possible to amplify gyrB fragments selectively from M．glucosida ，M．haemolytica or M．varigena ． These observations emphasize that biochemical，serological and genetic characterization is necessary for the proper identification of these organisms．Mannheimia 属菌の野外分離状況を16S rRNA 遺伝子の塩基配列解析により調査した. 生化学性状によりM．haemolytica と同定された133 株中31 株は, M．haemolytica以外の菌種であった. 一方, 血清型別試験で血清型が決定された菌株の96.0％がM．haemolytica であった. 他のMannheimia 属菌の菌種分類についても, gyrB は16S rRNA に比較して有用な遺伝子と考えられた. 本遺伝子を対象にしたMultiplex PCR 法による菌種同定法を検討し, 良好な結果が得られた. Mannheimia 属菌を正確に同定するには, 生化学性状試験と血清型別試験に加え, 遺伝子配列の比較を行う必要性があると考えられる