Transmission of Francisella tularensis, the etiologic agent of tularemia, has been associated with various water sources. Survival of many waterborne pathogens within free-living amoeba (FLA) is well documented; however, the role of amoebae in the environmental persistence of F. tularensis is unclear. In this study, axenic FLA cultures of Acanthamoeba castellanii, Acanthamoeba polyphaga, and Vermamoeba vermiformis were each inoculated with virulent strains of F. tularensis (Types A and B), the attenuated live vaccine strain, and Francisella novicida. Experimental parameters included low and high multiplicity of infection and incubation temperatures of 25 and 30 °C for 0-10 days. Francisella spp. survival was enhanced by the presence of FLA; however, bacterial growth and protozoa infectivity were not observed. In contrast, co-infections of A. polyphaga and Legionella pneumophila, used as an amoeba pathogen control, resulted in bacterial proliferation, cytopathic effects, and amoebal lysis. Collectively, even though short-term incubation with FLA was beneficial, the long-term effects on Francisella survival are unknown, especially given the expenditure of available amoebal derived nutrients and the fastidious nature of Francisella spp. These factors have clear implications for the role of FLA in Francisella environmental persistence.

中文翻译：

---

提高了弗朗西斯菌的存活率，但没有扩增。在自由活动的变形虫存在下。

Tularemia的病原体Francisella tularensis的传播与各种水源有关。在自由生存的变形虫中，许多水生病原体的生存情况已有详尽记录；然而，变形虫在土拉弗朗西斯菌的环境持久性中的作用尚不清楚。在这项研究中，分别对灰叶棘阿米巴，多叶棘阿米巴和Vermamoeba vermiformis的无性FLA培养物接种了强毒的弗拉土耳霉菌菌株（A型和B型），减毒活疫苗株和新弗朗西斯菌。实验参数包括低和高感染复数以及25和30°C的0-10天孵育温度。弗朗西斯菌属 FLA的存在可提高生存率；但是，没有观察到细菌的生长和原生动物的感染性。相反，A的共同感染。多虫和嗜肺军团杆菌用作变形虫病原体控制，导致细菌增殖，细胞病变作用和变形虫溶解。总的来说，尽管短期与FLA孵育是有益的，但对弗氏杆菌生存的长期影响仍是未知的，特别是考虑到可用的变形虫营养成分的消耗以及弗氏杆菌的挑剔性质。这些因素对FLA在弗朗西斯菌环境持久性中的作用具有明显的含义。特别是考虑到可用的变形虫营养成分的消耗以及弗朗西斯菌属的挑剔性质。这些因素对FLA在弗朗西斯菌环境持久性中的作用具有明显的含义。尤其是考虑到可用的变形虫营养成分的消耗以及弗朗西斯菌属（Francisella spp）的挑剔性质。这些因素对FLA在弗朗西斯菌环境持久性中的作用具有明显的含义。