Gill Wendy P, Harik Nada S, Whiddon Molly R, Liao Reiling P, Mittler John E, Sherman David R
Division of Allergy and Infectious Diseases, University of Washington Medical Center, 1959 Northeast Pacific Street, Box 356523, Seattle, Washington 98195, USA.
Nat Med. 2009 Feb;15(2):211-4. doi: 10.1038/nm.1915. Epub 2009 Feb 1.
Few tools exist to assess replication of chronic pathogens during infection. This has been a considerable barrier to understanding latent tuberculosis, and efforts to develop new therapies generally assume that the bacteria are very slowly replicating or nonreplicating during latency. To monitor Mycobacterium tuberculosis replication within hosts, we exploit an unstable plasmid that is lost at a steady, quantifiable rate from dividing cells in the absence of antibiotic selection. By applying a mathematical model, we calculate bacterial growth and death rates during infection of mice. We show that during chronic infection, the cumulative bacterial burden-enumerating total live, dead and removed organisms encountered by the mouse lung-is substantially higher than estimates from colony-forming units. Our data show that M. tuberculosis replicates throughout the course of chronic infection of mice and is restrained by the host immune system. This approach may also shed light on the replication dynamics of other chronic pathogens.
用于评估慢性病原体在感染期间复制情况的工具很少。这一直是理解潜伏性结核病的一个重大障碍，并且开发新疗法的努力通常假定细菌在潜伏期间复制非常缓慢或不复制。为了监测宿主内结核分枝杆菌的复制，我们利用一种不稳定的质粒，该质粒在没有抗生素选择的情况下，会以稳定、可量化的速率从分裂细胞中丢失。通过应用数学模型，我们计算了小鼠感染期间细菌的生长和死亡率。我们表明，在慢性感染期间，累积细菌负荷（计算小鼠肺部遇到的活的、死的和清除的生物体总数）大大高于集落形成单位的估计值。我们的数据表明，结核分枝杆菌在小鼠慢性感染过程中持续复制，并受到宿主免疫系统的抑制。这种方法也可能有助于揭示其他慢性病原体的复制动态。
