摘要

自从引入肺炎球菌结合疫苗以来，非美罗培南易感性肺炎球菌在日本的患病率一直在上升。在较早的研究中，我们证明了日本具有多重耐药性的血清型15A-ST63具有特定的pbp1a序列（pbp1a-13），可以促进美罗培南的耐药性。为了追踪pbp1a的起源，我们分析了血清型19A-CC3111的分离株，它是日本最流行的非美罗培南敏感克隆。我们使用全基因组测序分析了在日本回收的总共119种血清型19A-CC3111菌株。在119个分离株中，有53个（44.5％）带有pbp1a-13，这表明该克隆可能是pbp1a型的主要宿主，并且pbp1a区域可能在不同血清型菌株之间水平转移。单次获得pbp1a-13似乎只引起青霉素耐药，而不引起多药耐药。 pbp2b和/或pbp2x区域青霉素结合蛋白（PBP）重组与获得pbp1a-13的组合引起多药耐药性。保守的氨基酸基序分析表明，pbp1a 370SXXK，pbp2b 448SXN和pbp2x 337SXXN基序是氨基酸替代的候选对象，可提高美罗培南，头孢噻肟和青霉素的MIC。我们确定了与多药耐药性相关的特定克隆，尽管在使用核心基因组生成的系统树和仅使用cps基因座生成的系统树之间未发现相关性。所有测试的分离株均具有高度的红霉素抗性，并且大多数在大环内酯外排遗传装配（MEGA）元件和Tn917内的ermB中带有mefE，并插入Tn916内，并显示与Tn2017相同的结构。

Since the introduction of pneumococcal conjugate vaccines, the prevalence of non-meropenem-susceptible pneumococci has been increasing in Japan. In an earlier study, we demonstrated that multidrug-resistant serotype 15A-ST63 in Japan has a specific pbp1a sequence (pbp1a-13) that could promote meropenem resistance. To trace the origin of pbp1a, we analyzed isolates of serotype 19A-CC3111, which is the most prevalent non-meropenem-susceptible clone in Japan. We analyzed a total of 119 serotype 19A-CC3111 strains recovered in Japan using whole-genome sequencing. Of the 119 isolates, 53 (44.5%) harbored pbp1a-13, indicating that the clone may be the primary reservoir of the pbp1a type and that the pbp1a region may be horizontally transferred between different serotype strains. The single acquisition of pbp1a-13 seemed to cause only penicillin resistance and not multidrug resistance; a combination of penicillin-binding protein (PBP) recombination in the pbp2b and/or pbp2x region(s) with acquisition of pbp1a-13 caused multidrug resistance. Conserved amino acid motif analysis suggested that the pbp1a 370SXXK, pbp2b 448SXN, and pbp2x 337SXXN motifs were the candidates for amino acid substitutions increasing the MICs of meropenem, cefotaxime, and penicillin. We identified a specific clone that was correlated with multidrug resistance, although no correlation was observed between phylogenetic trees generated using core genomes and those generated with only the cps locus. All tested isolates were highly erythromycin resistant, and most harbored mefE within macrolide efflux genetic assembly (MEGA) elements and ermB within Tn917, which was inserted within Tn916 and exhibited a structure identical to that of Tn2017.

https://aac.asm.org/content/63/9/e00711-19.abstract