Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, PA, USA.
J Infect Dis. 2011 Jul 1;204(1):51-9. doi: 10.1093/infdis/jir221.
Francisella tularensis is the causative agent of tularemia and is classified as a category A biodefense agent by the Centers for Disease Control and Prevention because of its highly infectious nature. F. tularensis infects leukocytes and exhibits an extracellular phase in the blood of the host. It is unknown, however, whether F. tularensis can infect erythrocytes; thus, we examined this possibility in vivo and in vitro. In the murine model of pulmonary type A tularemia, we showed the presence of intraerythrocytic bacteria by double-immunofluorescence microscopy and ex vivo gentamicin protection of the purified erythrocyte fraction. In vitro, F. tularensis invaded human erythrocytes, as shown in the gentamicin protection assays, double-immunofluorescence microscopy, flow cytometry, scanning electron microscopy, and transmission electron microscopy with immunogold labeling of the bacteria. Additional in vitro tests indicated that serum complement-dependent and complement-independent mechanisms contribute to erythrocyte invasion. Our results reveal a novel intraerythrocytic phase during F. tularensis infection.
土拉弗朗西斯菌是兔热病的病原体，因其高度传染性而被疾病预防控制中心归类为 A 类生物防御剂。土拉弗朗西斯菌感染白细胞，并在宿主血液中表现出细胞外阶段。然而，尚不清楚土拉弗朗西斯菌是否可以感染红细胞；因此，我们在体内和体外检查了这种可能性。在 A 型肺型兔热病的小鼠模型中，我们通过双重免疫荧光显微镜和体外庆大霉素保护纯化的红细胞部分显示了红细胞内细菌的存在。在体外，土拉弗朗西斯菌侵入人红细胞，如庆大霉素保护试验、双重免疫荧光显微镜、流式细胞术、扫描电子显微镜和用细菌免疫金标记的透射电子显微镜所示。额外的体外试验表明，血清补体依赖性和补体非依赖性机制有助于红细胞入侵。我们的结果揭示了土拉弗朗西斯菌感染期间的一个新的红细胞内阶段。
