Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 20814-4799, USA.
Infect Immun. 2011 Aug;79(8):3012-9. doi: 10.1128/IAI.00205-11. Epub 2011 May 16.
Bacillus cereus G9241 was isolated from a welder with a pulmonary anthrax-like illness. The organism contains two megaplasmids, pBCXO1 and pBC218. These plasmids are analogous to the Bacillus anthracis Ames plasmids pXO1 and pXO2 that encode anthrax toxins and capsule, respectively. Here we evaluated the virulence of B. cereus G9241 as well as the contributions of pBCXO1 and pBC218 to virulence. B. cereus G9241 was avirulent in New Zealand rabbits after subcutaneous inoculation and attenuated 100-fold compared to the published 50% lethal dose (LD(50)) values for B. anthracis Ames after aerosol inoculation. A/J and C57BL/6J mice were comparably susceptible to B. cereus G9241 by both subcutaneous and intranasal routes of infection. However, the LD(50)s for B. cereus G9241 in both mouse strains were markedly higher than those reported for B. anthracis Ames and more like those of the toxigenic but nonencapsulated B. anthracis Sterne. Furthermore, B. cereus G9241 spores could germinate and disseminate after intranasal inoculation into A/J mice, as indicated by the presence of vegetative cells in the spleen and blood of animals 48 h after infection. Lastly, B. cereus G9241 derivatives cured of one or both megaplasmids were highly attenuated in A/J mice. We conclude that the presence of the toxin- and capsule-encoding plasmids pBCXO1 and pBC218 in B. cereus G9241 alone is insufficient to render the strain as virulent as B. anthracis Ames. However, like B. anthracis, full virulence of B. cereus G9241 for mice requires the presence of both plasmids.
蜡样芽胞杆菌 G9241 从一名患有肺炭疽样疾病的焊工身上分离得到。该生物体含有两个大型质粒，pBCXO1 和 pBC218。这些质粒类似于炭疽芽孢杆菌 Ames 质粒 pXO1 和 pXO2，分别编码炭疽毒素和荚膜。在此，我们评估了蜡样芽胞杆菌 G9241 的毒力以及 pBCXO1 和 pBC218 对毒力的贡献。经皮下接种后，新西兰兔对蜡样芽胞杆菌 G9241 无致病性，与炭疽芽孢杆菌 Ames 的公布 50%致死剂量 (LD50) 相比，其毒力减弱了 100 倍。通过皮下和鼻内途径感染，A/J 和 C57BL/6J 小鼠对蜡样芽胞杆菌 G9241 均具有相似的易感性。然而，在两种小鼠品系中，蜡样芽胞杆菌 G9241 的 LD50 明显高于炭疽芽孢杆菌 Ames 的 LD50，更类似于无荚膜但产毒的炭疽芽孢杆菌 Sterne。此外，经鼻内接种到 A/J 小鼠后，蜡样芽胞杆菌 G9241 孢子能够发芽和传播，感染后 48 小时，动物的脾脏和血液中存在营养细胞。最后，去除一个或两个大型质粒的蜡样芽胞杆菌 G9241 衍生物在 A/J 小鼠中高度减毒。我们得出结论，在蜡样芽胞杆菌 G9241 中仅存在编码毒素和荚膜的质粒 pBCXO1 和 pBC218 不足以使该菌株具有与炭疽芽孢杆菌 Ames 相同的毒力。然而，与炭疽芽孢杆菌一样，蜡样芽胞杆菌 G9241 对小鼠的完全毒力需要这两个质粒同时存在。
