Aix Marseille Université, Laboratoire de Chimie Bactérienne (UMR7283), Institut de Microbiologie de la Méditerranée - CNRS, 31, Chemin Joseph Aiguier, 13402 Marseille, France.
BMC Microbiol. 2014 Jan 2;14:3. doi: 10.1186/1471-2180-14-3.
Legionella pneumophila is a waterborne pathogen responsible for Legionnaires' disease, an infection which can lead to potentially fatal pneumonia. After disinfection, L. pneumophila has been detected, like many other bacteria, in a "viable but non culturable" state (VBNC). The physiological significance of the VBNC state is unclear and controversial: it could be an adaptive response favoring long-term survival; or the consequence of cellular deterioration which, despite maintenance of certain features of viable cells, leads to death; or an injured state leading to an artificial loss of culturability during the plating procedure. VBNC cells have been found to be resuscitated by contact with amoebae.
We used quantitative microscopic analysis, to investigate this "resuscitation" phenomenon in L. pneumophila in a model involving amending solid plating media with ROS scavengers (pyruvate or glutamate), and co-culture with amoebae. Our results suggest that the restoration observed in the presence of pyruvate and glutamate may be mostly due to the capacity of these molecules to help the injured cells to recover after a stress. We report evidence that this extracellular signal leads to a transition from a not-culturable form to a culturable form of L. pneumophila, providing a technique for recovering virulent and previously uncultivated forms of L. pneumophila.
These new media could be used to reduce the risk of underestimation of counts of virulent of L. pneumophila cells in environmental samples.
嗜肺军团菌是一种水生病原体，可引起军团病，这是一种可能导致致命性肺炎的感染。经过消毒后，嗜肺军团菌像许多其他细菌一样，处于“可存活但不可培养”（VBNC）状态。VBNC 状态的生理意义尚不清楚且存在争议：它可能是一种有利于长期生存的适应性反应；或者是细胞恶化的结果，尽管维持了存活细胞的某些特征，但导致死亡；或者是一种受伤状态，导致在接种过程中人为丧失可培养性。已经发现 VBNC 细胞在与变形虫接触时会复苏。
我们使用定量显微镜分析，在涉及用活性氧（ROS）清除剂（丙酮酸或谷氨酸）修饰固体接种培养基并与变形虫共培养的模型中，研究了嗜肺军团菌中的这种“复苏”现象。我们的结果表明，在存在丙酮酸和谷氨酸的情况下观察到的恢复可能主要归因于这些分子在压力后帮助受伤细胞恢复的能力。我们报告的证据表明，这种细胞外信号导致嗜肺军团菌从不可培养形式向可培养形式的转变，为恢复有毒和以前未培养的嗜肺军团菌形式提供了一种技术。
这些新的培养基可用于降低低估环境样本中有毒嗜肺军团菌细胞计数的风险。
