摘要

       在35个月的时间里，从日本一家地区医院的老年患者中检测到青霉素敏感性降低（PRGBS）的B组链球菌，伴随着PRGBS血清型的人群水平转变。本文分析了73例77个非重复性PRGBS的遗传相关性。在最初的9个月（第一阶段），以血清型Ⅲ型PRGBS为主（16个血清型Ⅲ/1个血清型Ib），然后在接下来的3个月（第二阶段）内短暂出现3个血清型Ib菌株，在接下来的9个月（第三阶段）内主要被血清型Ia（20个血清型Ia/1个血清型Ⅲ/1个不可分型）所取代。在过去14个月（第四阶段），除了25个血清型Ia分离株外，还鉴定出10个血清型III。血清型I I I和I a菌株属于ST1，共用G329V、G398A、V405A和G429D替换青霉素结合蛋白2X。在三株进行全基因组测序的菌株中，血清型III菌株SU12（Ⅰ期）与血清型Ia菌株SU97（Ⅲ期）的基因组相似度高于血清型Ib菌株SU67（Ⅱ期）基于平均核苷酸同一性和单核苷酸多态性。对cps基因簇和上下游侧翼序列的分析表明，插入IS1548后，位于cpsY上游的透明质酸酶基因在SU12株中被破坏，而在SU97株中，插入了位于cpsL下游的tRNA-Arg和rpsA基因之间的ΔISSag8。有趣的是，大多数在第四期重新出现的Ⅲ型PRGBS都有tRNA-Arg-ΔISSag8-rpsA区域。囊膜转换和医院内传播可能有助于ST1 PRGBS分离株群体水平的血清型置换。

       Over a 35-month period, group B Streptococcus isolates with reduced penicillin susceptibility (PRGBS) were detected from elderly patients at a regional hospital in Japan, accompanying population-level transition of PRGBS serotypes. The genetic relatedness of 77 non-duplicate PRGBS from 73 patients was analysed. Serotype III PRGBS predominated (16 serotype III/1 serotype Ib) in the first 9 months (period I), then 3 serotype Ib isolates appeared transiently for the next 3 months (period II), which was replaced predominantly by serotype Ia (20 serotype Ia/1 serotype III/1 non-typeable) for 9 months (period III). In the last 14 months (period IV), besides 25 serotype Ia isolates, 10 serotype III were also identified. Serotypes III and Ia isolates, belonging to ST1, shared G329V, G398A, V405A and G429D substitutions in penicillin-binding protein 2X. Of three strains subjected to whole-genome sequencing, serotype III strain SU12 (period I) had a higher degree of genomic similarity with serotype Ia strain SU97 (period III) than serotype Ib strain SU67 (period II) based on average nucleotide identity and single nucleotide polymorphisms. Analysis of the cps gene clusters and the upstream and downstream flanking sequences revealed that disruption of the hyaluronidase gene located upstream of cpsY by insertion of IS1548 was found in strain SU12, whereas ΔISSag8 was inserted between tRNA-Arg and rpsA genes located downstream of cpsL in strain SU97. Interestingly, most serotype III PRGBS re-emerging in period IV had this tRNA-Arg-ΔISSag8-rpsA region. Capsular switching and nosocomial transmission may possibly contribute to population-level serotype replacement among ST1 PRGBS isolates.

        https://www.sciencedirect.com/science/article/abs/pii/S0924857918303285?via%3Dihub