Casson Nicola, Medico Noël, Bille Jacques, Greub Gilbert
Center for Research on Intracellular Bacteria, Microbiology Institute, Faculty of Biology and Medicine, University of Lausanne, Bugnon 48, 1011 Lausanne, Switzerland.
Microbes Infect. 2006 Apr;8(5):1294-300. doi: 10.1016/j.micinf.2005.12.011. Epub 2006 Mar 15.
Parachlamydia acanthamoebae is a Chlamydia-like organism that naturally infects free-living amoebae. P. acanthamoebae is a putative emerging agent of community-acquired and inhalation pneumonia that may enter and multiply within human macrophages. However, since Parachlamydia induces their apoptosis, macrophages may not represent a perennial niche for this obligate intracellular bacterium. Therefore, we investigated whether pneumocytes and lung fibroblasts are permissive to Parachlamydia infection and might act as a replicative niche. Entry of Parachlamydia into pneumocytes (A549) and lung fibroblasts (HEL) was confirmed by confocal and electron microscopy. In A549 cells, the mean number of Parachlamydia per cell increased 7-fold from day 0 to day 7, independently of the technique used to label the bacteria. The proportion of infected A549 cells also increased over time, whereas cell viability remained unaffected by Parachlamydia infection. The sustained (3 weeks) viability of Parachlamydia when incubated in the presence of A549 cells contrasted with that observed in the absence of cells. HEL cells were also permissive to Parachlamydia infection, as we observed a 3- to 4-fold increase in the mean number of bacteria per cell. In HEL cells, Parachlamydia retained some viability for 2 weeks. These findings demonstrate that Parachlamydia is able to enter and multiply within pneumocytes and fibroblasts. The viability of both cell types was not compromised after Parachlamydia infection. We therefore conclude that these cells may remain infected for a prolonged time and may represent an intrapulmonary niche for the strictly intracellular Parachlamydia. This indirectly supports the role of Parachlamydia as an agent of pneumonia.
棘阿米巴属副衣原体是一种类似衣原体的微生物，可自然感染自由生活的阿米巴。棘阿米巴属副衣原体是社区获得性肺炎和吸入性肺炎的一种潜在新兴病原体，它可能进入人类巨噬细胞并在其中繁殖。然而，由于副衣原体可诱导巨噬细胞凋亡，因此巨噬细胞可能并非这种专性胞内细菌的长期生存微环境。因此，我们研究了肺细胞和成纤维细胞是否允许副衣原体感染，并可能作为其复制微环境。通过共聚焦显微镜和电子显微镜证实了副衣原体进入肺细胞（A549）和成纤维细胞（HEL）。在A549细胞中，从第0天到第7天，每个细胞中副衣原体的平均数量增加了7倍，这与用于标记细菌的技术无关。随着时间的推移，被感染的A549细胞比例也增加，而细胞活力不受副衣原体感染的影响。在A549细胞存在的情况下孵育时，副衣原体可持续存活（3周），这与无细胞时的情况形成对比。HEL细胞也允许副衣原体感染，因为我们观察到每个细胞中细菌的平均数量增加了3至4倍。在HEL细胞中，副衣原体可保持约2周的活力。这些发现表明，副衣原体能够进入肺细胞和成纤维细胞并在其中繁殖。副衣原体感染后，这两种细胞类型的活力均未受损。因此，我们得出结论，这些细胞可能会被长期感染，并可能代表严格胞内寄生的副衣原体在肺内的生存微环境。这间接支持了副衣原体作为肺炎病原体的作用。
