Department of Infectious Diseases, Medical Mycology Research Center, Chiba University, Chiba, Japan.
Department of Infectious Diseases, Medical Mycology Research Center, Chiba University, Chiba, Japan.
J Infect Chemother. 2019 Oct;25(10):750-757. doi: 10.1016/j.jiac.2019.02.007. Epub 2019 Jun 22.
The prevalence of nonencapsulated Streptococcus pneumoniae (NESp) has increased with the introduction of pneumococcal conjugate vaccines in children; however, the bacteriological characteristics of NESp have not been sufficiently clarified. In this study, NESp strains isolated from the nasopharyngeal carriage of children from four nursery schools in Japan were analyzed for molecular type, antibiotic susceptibility, and biofilm productivity. A total of 152 putative S. pneumoniae strains were identified by optochin-susceptibility analysis, of which 21 were not serotypeable by slide agglutination, quellung reaction, or multiplex PCR. Among these 21 strains, three were lytA-negative and, therefore, not S. pneumoniae. The remaining 18 strains were positive for lytA, ply, pspK, and bile solubility and were confirmed as NESp. Therefore, the isolation rate of NESp in the S. pneumoniae strains in this study was 12.0% (18/149). Molecular-typing analyses classified five strains as two existing sequence types (STs; ST7502 and ST7786), and 13 strains formed four novel STs. Horizontal spread was suspected, because strains with the same ST were often isolated from the same nursery school. The NESp isolates were generally susceptible to most antimicrobials, with the exception of macrolides; however, all isolates possessed more than one abnormal penicillin-binding protein gene. Furthermore, NESp strains were more effective than encapsulated counterparts at forming biofilms, which showed obvious differences in morphology. These data indicated that NESp strains should be continuously monitored as emerging respiratory pathogens.
未被荚膜包裹的肺炎链球菌（NESp）的流行率随着儿童用肺炎球菌结合疫苗的引入而增加；然而，NESp 的细菌学特征尚未得到充分阐明。在这项研究中，分析了从日本四所托儿所儿童鼻咽携带物中分离出的 NESp 菌株的分子型、抗生素敏感性和生物膜生成能力。通过对Optochin 敏感性分析鉴定了 152 株疑似肺炎链球菌，其中 21 株不能通过玻片凝集、Quellung 反应或多重 PCR 进行血清型鉴定。在这 21 株中，3 株 lytA 阴性，因此不是肺炎链球菌。其余 18 株 lytA、ply、pspK 和胆汁溶解度均为阳性，被确认为 NESp。因此，本研究中肺炎链球菌株中 NESp 的分离率为 12.0%（18/149）。分子分型分析将 5 株分为两种现有序列型（ST；ST7502 和 ST7786），13 株形成 4 种新的 ST。由于具有相同 ST 的菌株经常从同一托儿所分离出来，因此怀疑存在水平传播。除了大环内酯类药物外，NESp 分离株通常对大多数抗生素敏感；然而，所有分离株都具有不止一个异常青霉素结合蛋白基因。此外，与有荚膜的对应物相比，NESp 菌株更有效地形成生物膜，其形态明显不同。这些数据表明，应作为新兴呼吸道病原体持续监测 NESp 菌株。
