荚膜A型多杀性巴氏杆菌引起牛纤维素性化脓性肺炎:病原引起疾病因果关系的确定

Bovine fibrino suppurative broncho pneumoniais caused by Pasteurella multocida capsular type A: determination of the cause-and-effect relationship between the pathogen and the disease

2006年底本研究室在牛群中发现了病因不明的牛纤维素性化脓性肺炎疫情,该疫情已蔓延至中国的多个养牛地区,本研究室从发病牛肺脏中分离得到荚膜A型多杀性巴氏杆菌。为确定该菌与牛纤维素性化脓性肺炎的病原-疾病因果关系,本研究从病原流行病学调查、病原对实验动物的致病性与免疫保护性以及病原回归本动物致病特征3个方面,对其进行验证性研究。调查结果显示,在2008年~2014年采集的88份发病牛肺脏样品中,荚膜A型多杀性巴氏杆菌的PCR阳性率高达86.36%,而且PCR阳性样品中该菌的分离率高达90.79%。将现地分离株接种小鼠进行动物实验,结果显示,该菌具有高度致死性,而且灭活菌体接种小鼠对活菌攻击呈现良好的免疫保护性。动物回归试验结果显示,健康犊牛接种该分离菌株后出现与自然感染病例相似的纤维素性化脓性肺炎,免疫组化试验显示该菌株分布于病变肺组织、并从中重新分离出接种的病原菌。上述研究结果符合病原微生物鉴定的科赫法则,因此确定荚膜A型多杀性巴氏杆菌是引起牛纤维素性化脓性肺炎的病原。荚膜A型多杀性巴氏杆菌与牛纤维素性化脓性肺炎病原-疾病因果关系的确立,为该新发疫情防控技术的研究提供了参考依据、奠定了实验基础。

Abstract： Severe fibrino suppurative broncho pneumonia was observed in cattle herds in China in 2006 when its pathogen was unknown. Until 2008 when the disease had been spread in many cattle breeding regions of China, Pasteurella mutocida capsular type A was isolated from lungs of the diseased cattle. To determine Pasteurella multocida capsular type A as the causative agent of bovine fibrino suppurative broncho pneumonia, some studies were carried out for the bacteria, including epidemiological survey, lethality and immunoprotection in mice, and pathogenicity in cattle. The epidemiological surveys showed that the PCR positive rate and the isolation rate of Pasteurella multocida capsular type A in 88 collected samples were up to 86.36% and90.79%from 2008 to 2014, respectively. Furthermore, the mice inoculated with the isolate or its inactivated antigen exhibited high lethality or immunoprotection. More importantly, typical fibrino suppurative broncho pneumonia was reproduced in calves by artificial inoculation of the isolate, and additionally, the distribution of the inoculated bacteria was detected by immunohistochemical tests and the bacteria could also be recovered from the lung tissue with pathological damage. These experimental results followed the Koch＇s postulates, and therefore we determined that Pasteurella multocida capsular type A was the causative agent of fibrino suppurative bronchopneumonia in cattle. This study provids reference and experimental basis for studying preventive technologies against the Pasteurella multocida caosular Woe A-caused disease in cattle.