Kong Fanrong, Lambertsen Lotte Munch, Slotved Hans-Christian, Ko Danny, Wang Hui, Gilbert Gwendolyn L
Centre for Infectious Diseases and Microbiology, Institute of Clinical Pathology and Medical Research, Westmead Hospital, Darcy Road, Westmead, New South Wales 2145, Australia.
J Clin Microbiol. 2008 Aug;46(8):2745-50. doi: 10.1128/JCM.00189-08. Epub 2008 Jun 18.
Among 1,762 isolates of Streptococcus agalactiae (group B streptococcus [GBS]), 207 (12%) initially nonserotypeable isolates were tested by improved conventional serotyping methods (Lancefield antigen extraction with 0.1 and 0.2 N HCl, latex agglutination assays, and use of antisera against all known serotypes [Ia, Ib, and II to IX]) and a molecular serotype identification system (multiplex PCR-based reverse line blot [mPCR/RLB] assays targeting serotype-specific sites in the region spanning cpsH to cpsM). Serotypes were assigned to 71 (34%) of the 207 isolates by using antisera and to 204 (98.5%) of them by mPCR/RLB. Sequencing of a portion of the cpsE-cpsF-cpsG region of 141 persistently nonserotypeable isolates and 1 with discrepant conventional and molecular serotyping results was attempted. Major mutations were identified in 34 isolates (24%), including 11 (8%) from which no amplicons were obtained and 23 (16%) with sequence variation compared with published sequences; of the latter, 21 (15%) were associated with amino acid changes. By contrast, mutations were identified in only 12 (2.3%) of 516 serotypeable isolates for which this region has been sequenced previously. In summary, an improved serotyping scheme allowed serotype identification of more than one-third of the previously nonserotypeable GBS isolates. Molecular serotypes were assigned to almost all of the isolates by mPCR/RLB. Significant mutations (with no amplicons or with associated amino acid changes) were found in the cpsE-cpsF-cspG region of a higher proportion of nonserotypeable than of serotypeable isolates (32/141 versus 8/516; P < 0.001), but further investigation is needed to determine the genetic basis for most nonserotypeable GBS isolates.
在1762株无乳链球菌（B组链球菌[GBS]）分离株中，对207株（12%）最初无法进行血清分型的分离株采用改良的传统血清分型方法（用0.1 N和0.2 N盐酸提取兰斯菲尔德抗原、乳胶凝集试验以及使用针对所有已知血清型[Ia、Ib和II至IX]的抗血清）和一种分子血清型鉴定系统（基于多重PCR的反向线印迹[mPCR/RLB]试验，靶向cpsH至cpsM区域中的血清型特异性位点）进行检测。通过使用抗血清，207株分离株中的71株（34%）被分型，而通过mPCR/RLB则有204株（98.5%）被分型。尝试对141株持续无法进行血清分型的分离株以及1株传统血清分型结果与分子血清分型结果不一致的分离株的cpsE - cpsF - cpsG区域的一部分进行测序。在34株（24%）分离株中鉴定出主要突变，包括11株（8%）未获得扩增子，以及23株（16%）与已发表序列相比存在序列变异；后者中，21株（15%）与氨基酸变化相关。相比之下，在之前已对该区域进行测序的516株可进行血清分型的分离株中，仅12株（2.3%）鉴定出突变。总之，一种改良的血清分型方案能够对超过三分之一之前无法进行血清分型的GBS分离株进行血清型鉴定。通过mPCR/RLB几乎为所有分离株确定了分子血清型。在无法进行血清分型的分离株中，cpsE - cpsF - cspG区域发现显著突变（无扩增子或伴有氨基酸变化）的比例高于可进行血清分型的分离株（32/141对8/516；P < 0.001），但需要进一步研究以确定大多数无法进行血清分型的GBS分离株的遗传基础。
