The lprG-p55 operon of Mycobacterium tuberculosis, M. bovis and M. avium strain D4ER has been identified as a virulence factor involved in the transport of toxic compounds. LprG is a lipoprotein that modulates the host immune response against mycobacteria, whereas P55 is an efflux pump that provides resistance to several drugs. In the present study we search for, and characterize, lprg and p55, putative virulence genes in Mycobacterium avium subsp. paratuberculosis (MAP) to generate a live-attenuated strain of MAP that may be useful in the future as live-attenuated vaccine. For this purpose, we generated and evaluated two mutants of MAP strain K10: one mutant lacking the lprG gene (ΔlprG) and the other lacking both genes lprG and p55 (ΔlprG–p55). None of the mutant strains showed altered susceptibility to first-line and second-line antituberculosis drugs or ethidium bromide, only the double mutant had two-fold increase in clarithromycin susceptibility compared with the wild-type strain. The deletion of lprG and of lprG-p55 reduced the replication of MAP in bovine macrophages; however, only the mutant in lprG-p55 grew faster in liquid media and showed reduced viability in macrophages and in a mouse model. Considering that the deletion of both genes lprG-p55, but not that of lprG alone, showed a reduced replication in vivo, we can speculate that p55 contributes to the survival of MAP in this animal model.

结核分枝杆菌、牛分枝杆菌和鸟分枝杆菌菌株 D4ER的lprG-p55操纵子已被鉴定为参与有毒化合物运输的毒力因子。LprG 是一种脂蛋白，可调节宿主对分枝杆菌的免疫反应，而 P55 是一种外排泵，可对多种药物产生抗性。在本研究中，我们在鸟分枝杆菌亚种中寻找并表征了lprg和p55，即假定的毒力基因。副结核病(MAP) 以产生 MAP 的减毒活株，该毒株可能在未来用作减毒活疫苗。为此，我们生成并评估了 MAP 菌株 K10 的两种突变体：一种突变体缺乏lprG基因（Δ lprG），另一种突变体同时缺乏lprG和p55基因（Δ lprG–p55）。没有突变株对一线和二线抗结核药物或溴化乙锭的敏感性发生改变，只有双突变株与野生型菌株相比，克拉霉素的敏感性增加了两倍。lprG和lprG-p55的缺失减少了牛巨噬细胞中 MAP 的复制；然而，只有突变体lprG-p55在液体培养基中生长更快，在巨噬细胞和小鼠模型中的生存​​能力降低。考虑到lprG-p55两个基因的缺失，而不是lprG单独的缺失，显示体内复制减少，我们可以推测p55有助于该动物模型中 MAP 的存活。