Rhodococcus equi is a saprophytic soil bacterium and intracellular pathogen that causes refractory suppurative pneumonia in foals and has emerged as a pathogenic cause of zoonotic disease. Several studies have reported human infections caused by R. equi harboring a recently described third type of virulence plasmid, the ruminant-associated pVAPN, which carries the vapN virulence determinant. Herein, we analyzed pathogenicity and genomic features of nine vapN-harboring R. equi isolated from human patients with and without HIV/AIDS. Four of these strains showed significant VapN production and proliferation in cultured macrophages. These strains were lethally pathogenic after inoculation with 1.0 × 10⁸ CFU in mice and reproduced a necrotizing granulomatous inflammation in the liver and spleen similar to that observed in humans. Additionally, we determined entire genome sequences of all nine strains. Lengths of sequences were 5.0–5.3 Mbp, and GC contents were 68.7 %–68.8 %. All strains harbored a 120- or 125-kbp linear plasmid carrying vapN (Type I or Type II pVAPN) classified on the basis of differences in the distal sequences on the 3′ side. Interestingly, VapN production differed significantly among strains harboring nearly identical types of pVAPN with variation limited to several SNPs and short base pair indels. The pVAPN sequences possessed by the VapN-producing strains did not retain any common genetic characteristics, and more detailed analyses, including chromosomal genes, are needed to further elucidate the VapN expression mechanism.

马红球菌是一种腐生土壤细菌和细胞内病原体，可引起小马驹难治性化脓性肺炎，并已成为人畜共患病的病原体。几项研究报告了由R引起的人类感染。equi含有最近描述的第三种毒力质粒，即反刍动物相关 pVAPN，它携带vapN毒力决定簇。在此，我们分析了九个带有vapN 的R 的致病性和基因组特征。平等从患有和未患有 HIV/AIDS 的人类患者中分离出来。其中四种菌株在培养的巨噬细胞中显示出显着的 VapN 产生和增殖。这些菌株在小鼠中接种 1.0 × 10 ⁸ CFU后具有致死性致病性，并在肝脏和脾脏中再现类似于在人类中观察到的坏死性肉芽肿性炎症。此外，我们确定了所有九个菌株的全基因组序列。序列长度为 5.0–5.3 Mbp，GC 含量为 68.7%–68.8%。所有菌株均含有携带vapN的 120-kbp 或 125-kbp 线性质粒（I 型或 II 型 pVAPN）根据 3' 侧远端序列的差异进行分类。有趣的是，VapN 产量在含有几乎相同类型 pVAPN 的菌株之间存在显着差异，其变异仅限于几个 SNP 和短碱基对插入缺失。产 VapN 菌株所拥有的 pVAPN 序列没有保留任何共同的遗传特征，需要更详细的分析，包括染色体基因，以进一步阐明 VapN 的表达机制。