牛源皮特不动杆菌对小鼠的致病性分析

为探究来源于牛呼吸道疾病综合征发病牛的皮特不动杆菌对小鼠的致病性,对其进行相关毒力基因的检测和小鼠致病性试验,试验内容主要包括临床症状观察、病理剖检、组织病理学观察,以及半数致死量(LD₅₀)和各器官载菌量的测定。结果显示,牛源皮特不动杆菌ZZCNC1807-6和ZZCSF1807-9菌株对小鼠均具有较强的致死性,对小鼠的LD₅₀分别为4.487×10⁷ CFU·mL^-1和3.177×10⁸ CFU·mL^-1。剖检死亡小鼠可见,牛源皮特不动杆菌主要造成小鼠皮下充血、肺淤血肿胀、肠道积气积液等症状,可引起心、肝、脾、肺、肾、脑等多种器官感染。组织病理学观察显示,小鼠各器官病变均较轻微,主要表现在肝、肺中有少量炎性细胞浸润,脾中白髓细胞坏死和纤维增生,其中ZZCNC1807-6攻菌组的病变较ZZCSF1807-9攻菌组相对严重。载菌量分析结果显示,2株菌对小鼠肝、心、脾、肺和肾的侵袭力差异不大,但ZZCNC1807-6对脑的侵袭力强于ZZCSF1807-9。综上,ZZCNC1807-6菌株的毒力强于ZZCSF1807-9。

Pathogenicity of Acinetobacter pittii from beef cattle in mice

In order to explore the pathogenicity of two strains of Acinetobacter pittii from bovine respiratory disease complex (BRDC) infected beef cattle to mice, the related virulence genes were detected and the pathogenicity test of mice was carried out, which mainly included clinical symptom observation, pathological examination, histopathological observation, and determination of median lethal dosage (LD₅₀) and bacterial load in various organs. The results showed that ZZCNC1807-6 and ZZCSF1807-9 stains were highly lethal to mice, and their LD₅₀ reached 4.487×10⁷ CFU·mL^-1 and 3.177×10⁸ CFU·mL^-1, respectively. After pathology autopsy, it was seen that Acinetobacter pittii mainly caused subcutaneously hyperemia, lung congestion and swelling, intestinal pneumatosis and effusion and other symptoms in mice. And it could cause infection of many organs, such as heart, liver, spleen, lung, kidney and brain. Histopathological observation showed that the pathological changes of various organs in mice were mild, mainly manifested in a small amount of inflammatory cells infiltration in liver and lung, and necrosis and fibrous hyperplasia of white pulp cells in spleen. Among them, the pathological changes of mice in ZZCNC1807-6 group were more serious than those in ZZCSF1807-9 group. The analysis of bacterial load showed that the invasiveness of the two strains to the liver, heart, spleen, lung and kidney of mice had little difference, but ZZCNC1807-6 strain had stronger invasiveness to the brain than ZZCSF1807-9. To sum up, the virulence of strain ZZCNC1807-6 was stronger than that of ZZCSF1807-9.