耐药性监测和耐药机制研究显示青霉素不敏感肺炎链球菌（PRSP）耐药性逐渐增强，基因变异逐步积累。但我们发现当前流行的PRSP并不是耐药性增强的既往流行克隆；不同克隆的菌株青霉素MIC分布范围不同；特定克隆的MIC分布限于一定范围。因此，我们推测可以通过菌株的基因序列及其特点判断其可以获得的耐药变异，及其青霉素耐药性可能达到的水平。本项目拟对国内流行的不同青霉素MIC分布的克隆开展研究，首先以已知耐药基因为目标，找出高、低青霉素MIC分布克隆中敏感株所具有的与获得耐药性密切相关的分子标记；以此标记将临床菌株分为可产生低和高青霉素耐药性的菌株，选择菌株进行全基因组测序，进行SNP分析并确定可鉴别两组的分子标记；并在临床菌株中验证这些标记；以发现的分子标记尝试建立新的分型方法，并验证因此发现的新耐药变异在耐药机制中的作用。研究结果提升对耐药机制的认识，改进用药理念，有助于耐药防控措施的制定。

Several genes were involoved in the mechnism of penicillin resistance in Streptococcus pneumoniae (S.pneumoniae). The penicillin resistance of S.pneumoniae increased year by year. The genetic variation also be demonstrated accumulating rule step by step. The variation associated with high resistance can not plays its role without the genetic variation included in the low resistance. The population composition of penicillin resistance S.pneumoniae (PRSP) changed significantly in our survey. The epidemic strains of PRSP with high resistance in recent years did not show genetic relationship with the past strains spreading in the same region. The penicillin MIC of the isolates belonging to the same clone distribute in limited range. The MIC distribution ranges were different between the clones. We, therefore, deduced that the achived penicillin resistant level and the genes variation restricted by the gentic background. Some special rules must existe for the isolates from the same gentic population. Some molecular markers can be identified to evaluated the penicillin resistance level one isolate can achived in the futrue or in the treatment procedure. The project will include epidemic S.pneumoniae clones with different penicillin resistance isoalted from clinical work. The genetic marker will be looked for in the known resistant genes. The markers associated with resistance acquiration harbored in the susceptible strains belonging to high or low penicillin MIC range. Two group can be set up using these markers tested in the clinical isolates. Then, some isolates choosed from the two group will be sequenced the whole genomes. More genetic markers can be found to differenciate the two group after SNP analysis. New type method could be set up based on the genetic markers. The role of new variation in resistance suggested in the study will be proved by transformation trials.The results will benefit for the clinical treatment and for making stritages to control resistance of this bacteria.

耐药性监测和耐药机制研究显示青霉素不敏感肺炎链球菌（PRSP）的耐药性逐渐增强，基因变异逐步积累。但我们发现当前流行的PRSP并不是耐药性增强的既往流行克隆，不同克隆群菌株的青霉素MIC分布范围不同，特定克隆的MIC分布限于一定范围。因此，我们推测可以通过菌株的基因序列及其特点判断其可以获得的耐药变异，及其青霉素耐药性可能达到的水平。本项目对国内流行的不同青霉素MIC分布的克隆菌株展开研究，首先以已知耐药基因为目标，找出高、低青霉素MIC分布克隆中敏感株所具有的与获得耐药性密切相关的分子标记，以此标记将临床菌株分为可产生低和高青霉素耐药性的菌株，选择菌株进行全基因组测序，进行SNP分析并确定可鉴别两组的分子标记，并在临床菌株中验证这些标记，以发现的分子标记尝试建立新的分型方法，并验证因此发现的新耐药变异在耐药机制中的作用。研究过程中耐药基因的检测采用的是聚合酶链反应（PCR），抗生素敏感性检测采用E-test方法，全基因组测序委托专业的测序公司完成。研究结果进一步印证了我们的推断，不同克隆群菌株的抗生素MIC限定在某一范围，耐药性强的克隆逐渐替代耐药性弱得克隆成为主要的流行克隆。研究结果揭示了肺炎链球菌临床分离株常见序列型（STs）的青霉素MIC值分布规律，支持以STs为基础研究其青霉素耐药机制。肺炎链球菌临床分离株的STs与其青霉素MIC值，及其进一步获得更高水平青霉素耐药之间密切相关。提示对于临床肺炎链球菌来说，青霉素类(或β-内酰胺类)抗生素选择压力首先要筛选具有不同青霉素敏感水平克隆，在此基础上再选择可获得更高水平耐药的变异群体。因此，研究肺炎链球菌临床分离株青霉素耐药机制时，应基于菌株的遗传背景资料，才有可能确定菌株获得的耐药相关变异，明确具体的变异类型和位点。研究结果提升对耐药机制的认识，改进用药理念，有助于耐药防控措施的制定。