急性坏死性胰腺炎继发感染的幼猪模型建立

Establishment of young pig model of secondary infection of acute necrotizing pancreatitis

目的建立适合影像学研究的大动物ANP继发感染模型。方法将30只幼猪分为实验组（20只）与对照组（10只）。先采用主胰管逆行插管注射5％牛磺胆酸钠和5％胰蛋白酶混合液（0．5ml／kg体重）制备ANP模型，并将主胰管近端结扎。2—3d后采用CT引导下细针穿刺技术向胰腺坏死区内注射大肠杆菌（10^8／m1）3—4ml，对照组注入灭活大肠杆菌。制模后行多层螺旋CT增强扫描，并行CTSI评分。检测血WBC、血淀粉酶，做血液细菌培养。注射大肠杆菌后5d处死动物，于感染灶或坏死灶处抽液涂片及细菌培养，周围组织常规病理检测。结果实验组ANP继发感染成功率80．0％（16／20），共发现17处感染灶，感染灶细菌培养阳性率100％（17／17），血培养阳性率68．8％（11／16）；对照组制模成功率70．0％（7／10），剔除1头污染外，仅发现1处感染灶，细菌培养及血培养阳性率均为14．3％（1／7）。两组血WBC及淀粉酶在制模后均明显升高，变化趋势相似，但实验组血WBC明显高于同期对照组（P〈0．01）。两组CTSl分值均≥4分，严重程度均为中重度。结论在建立ANP模型基础上采用CT引导下向坏死区内注射细菌的方法可成功建立ANP继发感染大动物模型，尤其适合影像学研究。

Objective To establish a big animal model of secondary infection of acute necrotizing pancreatitis （ANP）. Methods Thirty young pigs were allocated to experiment group （ n = 20） or control group （ n = 10）. The ANP model was induced by retrograde injection of a mixture solution of 5% sodium taurocholate and 5% trypsin （0.5 ml/kg body weight） into the main pancreatic duct and ligation of the proximal end of the main pancreatic duct, and then the second step was injecting 3 - 4 ml living Escherichia coli （E coli） suspension （108/ml） to the necrotic area of the pancreas by fine needle aspiration technique under CT guidance in the experiment group, and by injecting 3 - 4 ml inactivated E eoli in the control group using the same method. Multi-slice spiral CT dynamic enhanced scan was performed in both groups 1 day and 2 or 3 days after ANP modeling and 5 days after bacterial injection to calculate the CTSI score. Serum amylase, blood WBC count and blood bacterial culture was performed in both groups. 5 days later, the animals were scarified to observe the infected or necrosis loci, and perform smear, bacterial culture and pathologic examinations of the tissue around the infected or necrosis loci. Results The ANP secondary infection model was successfully established in 16 of the 20 animals in the study group, with a success rate of the 80.0% （16/20）. There were 17 foci where the positive rate of bacterial culture was 100% （17/17 foci）, and the success rate of blood bacterial culture was 68.8%（11/16）. In the control group, the ANP model was established successfully in 7 of 10 animals （70%）, except for one case of contamination, only one foci was identified; the positive rate of bacterial culture and the success rate of blood bacterial culture was 14.3% （1/7）. Serum amylase and white blood WBC count increased with similar trends, WBC count in the study group was significantly higher than that in the control group （P 〈 0.01 ）. The mean CT severity index（CTSI） was all ≥4 in both groups, indicating the severity was moderate to severe. Conclusions A stable and reliable model of secondary infection of ANP in big could be established satisfactorily by injecting active E. coli into the pancreatic necrosis tissue under CT guidance, which helps further pathogenic mechanism studies and clinical studies, especially imaging studies.