Deutsches Zentrum für Herz-Kreislauf-Forschung (DZHK), Standort Berlin, Berlin, Germany.
Department of Cardiology, Charité, Universitaetsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany.
Clin Res Cardiol. 2021 Mar;110(3):323-331. doi: 10.1007/s00392-020-01669-y. Epub 2020 May 22.
In spite of the progress in antimicrobial and surgical therapy, infective endocarditis (IE) is still associated with a high morbidity and mortality. IE is characterized by bacterial biofilms of the endocardium, especially of the aortic and mitral valve leading to their destruction. About one quarter of patients with formal surgery indication cannot undergo surgery. This group of patients needs further options of therapy, but due to a lack of models for IE prospects of research are low. Therefore, the purpose of this project was to establish an in vitro model of infective endocarditis to allow growth of bacterial biofilms on porcine aortic valves, serving as baseline for further research.
A pulsatile two-chamber circulation model was constructed that kept native porcine aortic valves under sterile, physiologic hemodynamic and temperature conditions. To create biofilms on porcine aortic valves the system was inoculated with Staphylococcus epidermidis PIA 8400. Aortic roots were incubated in the model for increasing periods of time (24 h and 40 h) and bacterial titration (1.5 × 10 CFU/mL and 1.5 × 10 CFU/mL) with 5 L cardiac output per minute. After incubation, tissue sections were analysed by fluorescence in situ hybridization (FISH) for direct visualization of the biofilms. Pilot tests for biofilm growth showed monospecies colonization consisting of cocci with time- and inocula-dependent increase after 24 h and 40 h (n = 4). In n = 3 experiments for 24 h, with the same inocula, FISH visualized biofilms with ribosome-containing, and thus metabolic active cocci, tissue infiltration and similar colonization pattern as observed by the FISH in human IE heart valves infected by S. epidermidis.
These results demonstrate the establishment of a novel in vitro model for bacterial biofilm growth on porcine aortic roots mimicking IE. The model will allow to identify predilection sites of valves for bacterial adhesion and biofilm growth and it may serve as baseline for further research on IE therapy and prevention, e.g. the development of antimicrobial transcatheter approaches to IE.
尽管在抗菌和手术治疗方面取得了进展，但感染性心内膜炎（IE）仍然与高发病率和死亡率相关。IE 的特征是心内膜的细菌生物膜，特别是主动脉瓣和二尖瓣，导致它们被破坏。大约四分之一有明确手术适应证的患者无法接受手术。这群患者需要进一步的治疗选择，但由于缺乏 IE 研究模型，研究前景较低。因此，本项目的目的是建立一种体外 IE 模型，使细菌生物膜能够在猪主动脉瓣上生长，为进一步研究提供基线。
构建了一个脉动双室循环模型，在无菌、生理血液动力学和温度条件下保持天然猪主动脉瓣。为了在猪主动脉瓣上形成生物膜，系统接种表皮葡萄球菌 PIA 8400。将主动脉根部在模型中孵育不同时间（24 小时和 40 小时）和不同细菌滴度（1.5×10 CFU/mL 和 1.5×10 CFU/mL），每分钟 5 升心输出量。孵育后，通过荧光原位杂交（FISH）分析组织切片，直接观察生物膜。生物膜生长的初步试验显示，在 24 小时和 40 小时后，随着时间和接种物的增加，单种细菌定植呈球菌样（n=4）。在 n=3 的 24 小时实验中，使用相同的接种物，FISH 观察到含有核糖体且因此代谢活跃的球菌生物膜，组织浸润和与通过 FISH 观察到的人类 IE 心瓣膜中表皮葡萄球菌感染的生物膜相似的定植模式。
这些结果表明，成功建立了一种新型的体外模型，用于模拟 IE 的猪主动脉根部细菌生物膜生长。该模型将能够识别瓣膜中细菌粘附和生物膜生长的倾向部位，并可作为 IE 治疗和预防的进一步研究的基线，例如开发针对 IE 的抗菌经导管方法。
