Department of Health Science, Faculty of Health and Sports Science, Juntendo University, Inzai, Chiba, Japan.
Department of Microbiology and Immunology, Tokyo Women's Medical University School of Medicine, Shinjuku, Tokyo, Japan.
Infect Genet Evol. 2022 Aug;102:105314. doi: 10.1016/j.meegid.2022.105314. Epub 2022 Jun 5.
Rodentibacter spp. are opportunistic pathogens that are often isolated from the upper respiratory tracts of laboratory rodents. In particular, R. pneumotropicus and R. heylii require considerable caution in rodent colonies, as they cause lethal pneumonia in rodents. A new species, R. haemolyticus, has recently been classified in the genus, and a very closely related strain, Rodentibacter sp. strain JRC, has been isolated in Japan. This study focused on strain JRC by performing genomic and pathogenic analyses. Draft genome sequencing of strain JRC identified several genes coding for putative virulent proteins, including hemolysin and adhesin. Furthermore, we found a new RTX (repeats-in-structural toxin) toxin gene in the genome, which was predicted to produce a critical virulence factor (RTXIA) similar to Enterobacteriaceae. The concentrated culture supernatant containing RTX toxin (RTXIA) showed cytotoxicity toward RAW264.7 cells. Pre-incubation with anti-CD11a attenuated the cytolysis, suggesting that the concentrated culture supernatant containing RTXIA is cell surface LFA-1 mediated cytolysin. Experimental infection of strain JRC intranasally with 5 female BALB/c-Rag2 mice showed 60% lethality and was not significantly different from those of R. pneumotropicus ATCC 35149 using the log-rank test. Combined with our finding that RTXIA has an almost identical amino acid sequence (98% identity) to that of R. haemolyticus 1625/19, these results strongly suggest that RTXIA-producing strain JRC (and related R. haemolyticus) is pathogenic to immunodeficient rodents, and both agents should be excluded in laboratory rodent colonies.
螺杆菌属是机会性病原体，通常从实验动物的上呼吸道分离出来。特别是 R. pneumotropicus 和 R. heylii 在鼠群中需要特别注意，因为它们会导致啮齿动物致命性肺炎。最近，一个新的物种 R. haemolyticus 被归类于该属，并且在日本分离到了一种非常密切相关的菌株，螺杆菌属菌株 JRC。本研究通过基因组和致病性分析对 JRC 菌株进行了研究。JRC 菌株的草图基因组测序鉴定出了几个编码潜在毒力蛋白的基因，包括溶血素和黏附素。此外，我们在基因组中发现了一个新的 RTX（重复结构毒素）毒素基因，该基因预测会产生一种类似于肠杆菌科的关键毒力因子（RTXIA）。含有 RTX 毒素（RTXIA）的浓缩培养上清液对 RAW264.7 细胞具有细胞毒性。用抗 CD11a 预孵育可减弱细胞溶解，表明含有 RTXIA 的浓缩培养上清液是细胞表面 LFA-1 介导的细胞溶解素。用 5 只雌性 BALB/c-Rag2 小鼠进行 JRC 菌株鼻腔内感染实验，用对数秩检验发现其 60%的致死率与 R. pneumotropicus ATCC 35149 无显著差异。结合我们发现 RTXIA 与 R. haemolyticus 1625/19 的氨基酸序列几乎相同（98%的同一性），这些结果强烈表明，产生 RTXIA 的 JRC 菌株（和相关的 R. haemolyticus）对免疫缺陷啮齿动物具有致病性，并且这两种病原体都应从实验室啮齿动物群中排除。
