Menzies School of Health Research, Royal Darwin Hospital, Darwin, Northern Territory, Australia.
J Clin Microbiol. 2010 Mar;48(3):831-5. doi: 10.1128/JCM.01701-09. Epub 2009 Dec 30.
Nonserotypeable pneumococci (NSP) are commonly carried by Australian Indigenous children in remote communities. The purpose of this study was to characterize carriage isolates of NSP from Indigenous children vaccinated with the seven-valent pneumococcal conjugate vaccine (PCV7) and to use these data to guide decisions on reporting of NSP. A total of 182 NSP were characterized by BOX typing, antibiogram analysis, and multilocus sequence typing (MLST) of common BOX types. NSP positive for the wzg capsule gene were analyzed by a multiplex PCR-based reverse line blot hybridization assay (mPCR/RLB-H) targeting capsule genes to determine the serotype. Among 182 NSP, 49 BOX types were identified. MLST of 10 representative isolates found 7 STs, including ST448 (which accounted for 11% of NSP). Non-penicillin susceptibility was evident in 51% of the isolates. Pneumococcal wzg sequences were detected in only 23 (13%) NSP, including 10 that contained an approximately 1.2-kb insert in the region. mPCR/RLB-H identified serotype 14 wzy sequences in all 10 NSP, and 1 also contained a serotype 3-specific wze sequence. Among the remaining 13 wzg-positive NSP, few belonged to the serotypes represented in PCV7. It appears that most NSP identified in Australian Indigenous children are from a true nonencapsulated lineage. Few NSP represented serotypes in PCV7 that suppress capsular expression. High rates of carriage and penicillin resistance and the occasional presence of capsule genes suggest a role for NSP in the maintenance and survival of capsulated pneumococci. To avoid the inflation of pneumococcal carriage and antibiotic resistance rates, in clinical trials, we recommend separate reporting of rates of capsular strains and NSP and the exclusion of data for NSP from primary analyses.
无血清型肺炎球菌（NSP）在澳大利亚偏远社区的土著儿童中常被携带。本研究的目的是对接种 7 价肺炎球菌结合疫苗（PCV7）的土著儿童携带的 NSP 分离株进行特征描述，并利用这些数据来指导 NSP 报告的决策。对 182 株 NSP 进行了 BOX 分型、抗生素谱分析和常见 BOX 型的多位点序列分型（MLST）。通过针对荚膜基因的多重 PCR 基于反向线杂交分析（mPCR/RLB-H）对 wzg 荚膜基因呈阳性的 NSP 进行分析，以确定血清型。在 182 株 NSP 中，鉴定出 49 种 BOX 型。对 10 株代表性分离株的 MLST 分析发现 7 种 ST，包括占 NSP 11%的 ST448。51%的分离株对青霉素的敏感性降低。只有 23 株（13%）NSP 检测到肺炎球菌 wzg 序列，其中 10 株在该区域含有约 1.2kb 的插入。mPCR/RLB-H 在所有 10 株 NSP 中均鉴定出 14 型 wzy 序列，其中 1 株还含有 3 型特异性 wze 序列。在其余 13 株 wzg 阳性的 NSP 中，很少有属于 PCV7 中代表的血清型。似乎大多数在澳大利亚土著儿童中鉴定出的 NSP 都来自真正的无荚膜谱系。少数 NSP 代表 PCV7 中抑制荚膜表达的血清型。高携带率和青霉素耐药率以及偶尔存在荚膜基因表明 NSP 在外层囊泡肺炎球菌的维持和生存中发挥作用。为避免肺炎球菌携带和抗生素耐药率的膨胀，在临床试验中，我们建议单独报告荚膜菌株和 NSP 的比率，并从主要分析中排除 NSP 的数据。
