金黄色葡萄球菌和肺炎克雷伯菌血流感染小鼠模型的建立及评价

摘要

Objective To establish the reliable models for early diagnosis of bloodstream infec-tions by common clinical bacteria and to provide reliable experimental models for screening and validation of biomarkers in the early stage of bacterial bloodstream infections. Methods Strains of Staphylococcus aureus ( S. aureus) ATCC25923 and Klebsiella pneumoniae ( K. pneumoniae) ATCC700603 were used as experimen-tal strains. Different concentrations of bacterial suspensions were injected into mice through tail vein. LD50 (median lethal dose) was calculated by Karber method and the concentration of 1/2LD50 was used for injec-tion. The established mouse models were evaluated based on the changes in physical signs, body weights, white blood cells ( WBC) , platelets and IL-6 as well as the results of blood culture, PCR and HE staining. Results LD50 of S. aureus and K. pneumoniae to ICR mice were 8. 1×108 CFU/ml and 1. 11×109 CFU/ml, respectively. Body weights of mice decreased significantly at the time point of 24 h after infection. WBC counts in normal mice were about (1. 42±0. 66)×109/L, but increased in model groups at 3 h after bacteria challenge. Compared with the control group, WBC counts in model groups increased significantly at 6 h ( P<0. 05), followed by decreases. Two days after infection, WBC counts in model groups increased again andremained at high levels till the 7th day. However, PLT counts in the model groups dropped dramatically within 2 days as compared with that in control group (P<0. 05). Increase of IL-6 was detected in the early K. pneumoniae infection and the extent of that was larger than that in S. aureus infection. Results of the whole blood culture were all positive within 2 days after infection. PCR analysis confirmed that the bloodstream in-fection pathogens were S. aureus and K. pneumoniae. Alveolar exudation, edema and leukocyte infiltration were observed in lung and liver tissues with HE staining. Conclusion The mouse models of S. aureus and K. pneumoniae infections for early detection of bloodstream infections are successfully established. This study provides reliable animal models for further researches on early diagnosis of different pathogen-induced blood-stream infections.%目的 建立临床常见的细菌性血流感染早期诊断小鼠模型,为血流感染早期标志物的寻找和验证提供稳定可靠的实验模型.方法 选择金黄色葡萄球菌ATCC25923和肺炎克雷伯菌ATCC700603为实验菌株,将不同浓度的细菌悬液通过尾静脉注入小鼠体内,按Karber法计算半数致死量(LD50),以1/2LD50浓度注射小鼠,通过其体征、体重变化,白细胞(WBC)、血小板(PLT)、白细胞介素-6(IL-6)等指标变化,及血培养、PCR和HE染色结果等综合评价模型,验证造模效果.结果 金黄色葡萄球菌的LD50约8.1×108 CFU/ml,肺炎克雷伯菌的LD50约1.11×109 CFU/ml.小鼠感染24 h后体重明显下降.正常小鼠WBC为(1.42±0.66)×109/L,注射菌液3 h后开始升高,6 h后明显升高后下降,48 h后WBC再次升高,168 h后仍无明显下降,与对照组比较差异有统计学意义(P<0.05).PLT在感染后24 h内明显下降(P<0.05).IL-6含量在肺炎克雷伯菌感染后升高较早,且升高幅度较金黄色葡萄球菌明显.感染后48 h内小鼠全血培养结果均为阳性,PCR结果证实了血流感染病原菌为金黄色葡萄球菌和肺炎克雷伯菌.HE染色结果表明感染后肝和肺存在炎细胞浸润.结论 成功建立了金黄色葡萄球菌和肺炎克雷伯菌的小鼠血流感染模型,为血流感染的早期诊断和不同病原菌感染的鉴别诊断等研究提供了可靠的动物模型.