Kong Fanrong, Gidding Heather F, Berner Reinhard, Gilbert Gwendolyn L
Centre for Infectious Diseases and Microbiology (CIDM), Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, Darcy Road, Westmead, New South Wales 2145, Australia.
Department of Pediatrics, University Children's Hospital, D-79106 Freiburg, Germany.
J Med Microbiol. 2006 Jul;55(Pt 7):829-837. doi: 10.1099/jmm.0.46307-0.
The Cbeta protein (Bac) of Streptococcus agalactiae (group B streptococcus; GBS) is an IgA binding protein encoded by bac, of which at least 39 sequence types have been described, based on polymorphisms in the repeated region of the cell-wall-spanning domain ('bac sequence types'). Cbeta is usually found in serotype Ib, less commonly in serotype II, and rarely in other serotypes. The aim of this study was to examine the prevalence, variety and distribution, among GBS serotypes and between invasive and superficial isolates, of bac sequence types. A total of 1101 GBS isolates were tested, from 10 countries, with a bac-specific PCR, and amplicons from all 255 (23 %) with positive results were sequenced. Ninety-seven percent (184/190) of serotype Ib and 37 % of serotype II isolates were bac positive. The Calpha protein gene (bca) was present in 98 % (251/255), and insertion sequences IS1381 and IS861 in 94 % (239/255), of bac-positive isolates. The authors identified 59 bac sequence types belonging to 19 groups, based on length, from 496 to 946 bp, with up to six sequence variants (a-f) in each group. The median bac sequence length of invasive isolates was significantly shorter than that of superficial isolates overall (640 versus 586 bp; P < 0.001) and specifically for serotype Ib (541 versus 676 bp; P < 0.001), and invasive isolates were significantly (P < 0.001) more likely to have one or more 18 bp deletions relative to the original published bac sequence (X59771). bac sequence typing is a useful addition to the previously described genotyping system, and will help to predict relative virulence among S. agalactiae serotype Ib strains.
无乳链球菌（B族链球菌；GBS）的Cbeta蛋白（Bac）是一种由bac编码的IgA结合蛋白，基于细胞壁跨域重复区域的多态性（“bac序列类型”），已描述了至少39种序列类型。Cbeta通常存在于血清型Ib中，较少见于血清型II，很少见于其他血清型。本研究的目的是检测GBS血清型之间以及侵袭性和浅表性分离株之间bac序列类型的流行率、多样性和分布情况。对来自10个国家的总共1101株GBS分离株进行了bac特异性PCR检测，并对所有255株（23%）检测结果为阳性的扩增子进行了测序。血清型Ib分离株的97%（184/190）和血清型II分离株的37%为bac阳性。在bac阳性分离株中，98%（251/255）存在Calpha蛋白基因（bca），94%（239/255）存在插入序列IS1381和IS861。作者根据长度从496到946 bp确定了59种属于19个组的bac序列类型，每组最多有6个序列变体（a - f）。侵袭性分离株的bac序列中位数长度总体上显著短于浅表性分离株（640对586 bp；P < 0.001），血清型Ib特异性情况也是如此（541对676 bp；P < 0.001），并且侵袭性分离株相对于最初公布的bac序列（X59771）更有可能出现一个或多个18 bp缺失（P < 0.001）。bac序列分型是对先前描述的基因分型系统的有益补充，将有助于预测无乳链球菌血清型Ib菌株之间的相对毒力。
