Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
BMC Microbiol. 2010 Sep 24;10:246. doi: 10.1186/1471-2180-10-246.
Several mutations have been described as responsible for rifampicin resistance in Neisseria meningitidis. However, the intriguing question on why these strains are so rare remains open. The aim of this study was to investigate the protein content and to identify differential expression in specific proteins in two rifampicin resistant and one susceptible meningococci using two-dimensional electrophoresis (2-DE) combined with mass spectrometry.
In our experimental conditions, able to resolve soluble proteins with an isoelectric point between 4 and 7, twenty-three proteins have been found differentially expressed in the two resistant strains compared to the susceptible. Some of them, involved in the main metabolic pathways, showed an increased expression, mainly in the catabolism of pyruvate and in the tricarboxylic acid cycle. A decreased expression of proteins belonging to gene regulation and to those involved in the folding of polypeptides has also been observed. 2-DE analysis showed the presence of four proteins displaying a shift in their isoelectric point in both resistant strains, confirmed by the presence of amino acid changes in the sequence analysis, absent in the susceptible.
The analysis of differentially expressed proteins suggests that an intricate series of events occurs in N. meningitidis rifampicin resistant strains and the results here reported may be considered a starting point in understanding their decreased invasion capacity. In fact, they support the hypothesis that the presence of more than one protein differentially expressed, having a role in the metabolism of the meningococcus, influences its ability to infect and to spread in the population. Different reports have described and discussed how a drug resistant pathogen shows a high biological cost for survival and that may also explain why, for some pathogens, the rate of resistant organisms is relatively low considering the widespread use of a particular drug. This seems the case of rifampicin resistant meningococci.
已有多种突变被描述为导致脑膜炎奈瑟菌对利福平耐药的原因。然而，这些菌株为何如此罕见的问题仍未得到解答。本研究旨在使用二维电泳（2-DE）结合质谱法，研究两种利福平耐药和一种敏感脑膜炎奈瑟菌的蛋白质含量，并鉴定其差异表达的蛋白质。
在我们的实验条件下，能够分辨等电点在 4 到 7 之间的可溶性蛋白质，在两种耐药株与敏感株相比，发现了 23 种差异表达的蛋白质。其中一些参与主要代谢途径的蛋白质表达增加，主要是在丙酮酸和三羧酸循环的分解代谢中。还观察到基因调控和多肽折叠相关蛋白的表达减少。2-DE 分析显示，在两种耐药株中，有 4 种蛋白质的等电点发生了变化，序列分析证实存在氨基酸变化，而在敏感株中则不存在。
差异表达蛋白的分析表明，在利福平耐药的脑膜炎奈瑟菌菌株中发生了一系列复杂的事件，这里报告的结果可以被认为是理解其侵袭能力下降的起点。事实上，它们支持这样一种假设，即存在不止一种差异表达的蛋白质，这些蛋白质在脑膜炎奈瑟菌的代谢中起作用，影响其感染和在人群中传播的能力。已有多项报道描述和讨论了耐药病原体为何表现出较高的生存生物学代价，这也可以解释为什么对于某些病原体，考虑到某种特定药物的广泛使用，耐药生物的比例相对较低。利福平耐药的脑膜炎奈瑟菌就是这种情况。
