林麝肺源致病性大肠杆菌感染BALB/c小鼠模型的建立及评价

Establishment and evaluation of BALB/c mice challenge model with lung pathogenic Escherichia coli O78 of forest musk deer origin

摘要:

【背景】林麝肺源致病性大肠杆菌(Lung pathogenic Escherichia coli，LPEC)属于肠外致病性大肠杆菌(Extraintestinal pathogenic Escherichia coli，ExPEC)，是重要的人畜共患病病原菌之一。【目的】建立林麝肺源致病性大肠杆菌感染BALB/c小鼠模型，为研究林麝LPEC O78的致病性提供实验基础。【方法】采用实验室保存的林麝LPEC优势血清型O78菌株腹腔注射BALB/c小鼠，计算LD50，确定造模感染剂量，通过监测感染后体重、生化指标、器官中细菌定殖量变化，以及进行细菌分离鉴定和组织病理学检查，评价造模效果。【结果】确定了LPEC O78致BALB/c小鼠的LD50为3.6×108 CFU/mL。实验组小鼠于攻毒后3 h出现精神萎靡、食欲不振、反应迟钝，剖检见肺脏及肝脏肿大、小肠出血。24 h内体重下降3.2 g左右，随后缓慢升高。生化指标中除尿酸含量与对照组不显著(P>0.05)外，谷丙转氨酶、谷草转氨酶、总蛋白、白蛋白、磷、钙、镁、总胆红素、尿素、血糖、胆碱酯酶和乳酸脱氢酶等指标均高于对照组水平，且组间变化显著(P<0.05)。各器官均有细菌定殖，心、脾及肾脏24 h达到最高，肝、肺及肠道12 h达到最高，之后随时间逐渐减少。小鼠各器官有不同程度的炎性细胞浸润和细胞坏死。【结论】成功建立了林麝LPEC O78感染BALB/c小鼠模型，为林麝LPEC O78的发病机制、病理生理等方面的研究奠定了一定基础。

Abstract:

[Background] Lung pathogenic Escherichia coli (LPEC) belonging to extraintestinal pathogenic Escherichia coli was one of the important pathogens of zoonosis. [Objective] To establish a BALB/c mice challenge model of LPEC from forest musk deer for the study of pathogenicity of LPEC O78. [Methods] BALB/c mice were infected by LPEC O78 that was preserved in the laboratory, and the infection dose of model was determined by intraperitoneal inoculation to calculate LD50 (median lethal dose). The effect of mice model was evaluated based on monitoring the changes in bodyweight, biochemical indexes and bacterial colonization, and further evaluated by isolation of bacteria and histopathological examination. [Results] The LD50 of LPEC O78 in BALB/c mice was 3.6×108 CFU/mL. After infection, the challenge group showed that depressed, anorexic and sluggish symptom. Lung and liver enlarged, intestine hemorrhage was observed by necropsy after 3 h post-challenge. The bodyweight of mice decreased by 3.2 g within 24 h post-challenge, and then slowly increased. The biochemichel indexs of ALT, AST, TP, ALB, IP, Ca, Mg, TBIL, URIC, UREA, GLU, CHE and LDH in the challenge mice were higher than the mock mice (P<0.05), except the uric acid content (P>0.05). All organs had bacterial colonization, in which heart, spleen and kidney reached the highest at 24 h post-challenge whereas the time for highest colonization in liver, lung and intestine was 12 h post-challenge. Histopathological examination revealed different degree of inflammatory cell infiltration and necrosis. [Conclusion] This study successfully established the mice challenge model of LPEC O78 and laid a foundation for the future research of pathogenesis and pathophysiology of LPEC O78 from forest musk deer.