Groebel K, Hoelzle K, Wittenbrink M M, Ziegler U, Hoelzle L E
Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 270, 8057 Zurich, Switzerland.
Infect Immun. 2009 Feb;77(2):576-84. doi: 10.1128/IAI.00773-08. Epub 2008 Nov 17.
Mycoplasma suis belongs to the hemotrophic mycoplasma group and causes infectious anemia in pigs. According to the present state of knowledge, this organism adheres to the surface of erythrocytes but does not invade them. We found a novel M. suis isolate that caused severe anemia in pigs with a fatal disease course. Interestingly, only marginal numbers of the bacteria were visible on and between the erythrocytes in acridine orange-stained blood smears for acutely diseased pigs, whereas very high loads of M. suis were detected in the same blood samples by quantitative PCR. These findings indicated that M. suis is capable of invading erythrocytes. By use of fluorescent labeling of M. suis and examination by confocal laser scanning microscopy, as well as scanning and transmission electron microscopy, we proved that the localization of M. suis was intracellular. This organism invades erythrocytes in an endocytosis-like process and is initially surrounded by two membranes, and it was also found floating freely in the cytoplasm. In conclusion, we were able to prove for the first time that a member of the hemotrophic mycoplasma group is able to invade the erythrocytes of its host. Such colonization should protect the bacterial cells from the host's immune response and hamper antibiotic treatment. In addition, an intracellular life cycle may explain the chronic nature of hemotrophic mycoplasma infections and should serve as the foundation for novel strategies in hemotrophic mycoplasma research (e.g., treatment or prophylaxis).
猪支原体属于血营养支原体属，可引起猪的传染性贫血。根据目前的认知，这种微生物附着于红细胞表面，但并不侵入红细胞内部。我们发现了一种新型猪支原体分离株，它可导致猪严重贫血，并伴有致命的病程。有趣的是，在急性患病猪的吖啶橙染色血涂片中，仅在红细胞表面和之间可见少量细菌，而通过定量PCR在相同血样中检测到了非常高载量的猪支原体。这些发现表明猪支原体能够侵入红细胞。通过对猪支原体进行荧光标记，并利用共聚焦激光扫描显微镜以及扫描和透射电子显微镜进行检查，我们证明了猪支原体定位于细胞内。这种微生物通过类似内吞作用的过程侵入红细胞，最初被两层膜包围，并且还发现它在细胞质中自由漂浮。总之，我们首次能够证明血营养支原体属的一个成员能够侵入其宿主的红细胞。这种定殖应可保护细菌细胞免受宿主免疫反应的影响，并妨碍抗生素治疗。此外，细胞内生命周期可能解释了血营养支原体感染的慢性性质，并应为血营养支原体研究的新策略（如治疗或预防）奠定基础。
