This study investigated the association of Pasteurella multocida isolation and the molecular characteristics of the isolates with the presence of pneumonic lesions in lambs at slaughter to assess its importance as a causative agent of pneumonic pasteurellosis compared with Mannheimia haemolytica. P. multocida was isolated from the 13.9% and 2.7%, and M. haemolytica from the 36.4% and 26.8%, of lungs with and without lesions, respectively (P < 0.05). Both microorganisms were frequently coisolated (23.2% and 12.5% from lungs with and without lesions, respectively). Isolation of P. multocida alone exhibited greater strength of association with pneumonic lesions (OR 11.4; 95% CI 3.2–40.6) than that exhibited by M. haemolytica alone (OR 3.0; 95% CI 1.6–5.4). Cluster analysis grouped the lungs into four clusters characterized by the isolation of M. haemolytica or P. multocida alone (clusters 1 and 4), coisolation of both microorganisms (cluster 3), and isolation of neither (cluster 2). Cluster 4 lungs exhibited higher frequencies of pneumonic lesions (87.5%) and severe (20.8%) and moderate (25.0%) lesions. Lungs coinfected with both pathogens (cluster 3) did not exhibit a higher frequency of severe and moderate consolidation lesions (6.1% and 14.3%, respectively), suggesting that P. multocida and M. haemolytica do not act synergically to cause more severe pneumonic infections. The greater strength of association of P. multocida isolation with pneumonic lesions together with the higher severity of the lesions caused could indicate a greater role played by this pathogen in the aetiopathogenesis of pneumonic pasteurellosis in sheep than is commonly assumed.

本研究调查了多杀性巴氏杆菌分离物的关联和分离物的分子特征与屠宰羔羊肺炎病变的关系，以评估其与溶血曼氏杆菌相比作为肺炎巴氏病的病因的重要性。在有和没有病变的肺中，分别从13.9％和2.7％分离出多杀疟原虫，从36.4％和26.8％分离出溶血支原体（P <0.05）。经常将两种微生物共分离（分别从有病变和无病变的肺中分离出23.2％和12.5％）。的分离多杀性巴氏杆菌单独表现出与肺病变关联更大的强度（OR 11.4; 95％CI 3.2-40.6）高于表现出通过仅溶血支原体（OR 3.0； 95％CI 1.6–5.4）。聚类分析将肺分为四个聚类，其特征是单独分离溶血支原体或多杀性巴氏杆菌（聚类1和4），两种微生物共分离（聚类3）和两者都不分离（聚类2）。集群4肺表现出较高的肺部病变频率（87.5％）和严重（20.8％）和中度（25.0％）病变。两种病原体同时感染的肺（重度和中度合并病变）的发生率较高（分别为6.1％和14.3％），表明多杀性疟原虫和溶血支原体不能协同作用导致更严重的肺炎感染。更大的结社力量带有肺炎性病变的多杀毕赤酵母分离以及所引起的较高病变严重程度可能表明，这种病原体在绵羊肺炎性巴氏杆菌病的发病机理中的作用比通常认为的要大。