Genetic islands of Streptococcus agalactiae strains NEM316 and 2603VR and their presence in other Group B Streptococcal strains -: art. no. 31
Genetic islands of Streptococcus agalactiae strains NEM316 and 2603VR and their presence in other Group B Streptococcal strains -: art. no. 31
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DOI：
10.1186/1471-2180-5-31
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发表时间：
2005-05-24
期刊：
影响因子：
4.2
通讯作者：
Saunders, NJ
中科院分区：
文献类型：
--
作者：
Herbert, MA;Beveridge, CJE;Saunders, NJ
背景：无乳链球菌（B 族链球菌；GBS）是产科和新生儿细菌性败血症的主要致病因素。血清型 III 菌株导致大多数婴儿迟发性败血症和脑膜炎，因此与主要在免疫功能低下的孕妇中引起疾病的其他血清型相比，其似乎具有更强的侵袭能力。我们分别比较了菌株NEM316和2603VR的血清型III和V全基因组序列，试图鉴定菌株NEM316的遗传属性，这可能解释菌株NEM316引起婴儿迟发性疾病的倾向。 NEM316 菌株全基因组序列中描述了 14 个假定的致病性岛。使用 PCR 和靶向微阵列策略，在不同菌株集合中评估了这些岛的存在，包括来自健康孕妇的 18 个定植分离株，以及分别来自早发性和迟发性败血症婴儿的 13 个和 8 个侵入性分离株。 结果：菌株 NEM316 和菌株 2603VR 基因组的并排比较显示，它们极其相似，唯一的主要区别是包膜位点和移动遗传元件。 PCR 和比较基因组杂交 (CGH) 用于确定 39 个 GBS 分离株中每个岛的存在情况。只有 I、VI、XII 岛和可能的 X 岛符合真正致病性岛的标准，但在这 14 个岛中任何一个的存在与菌株是否具有侵入性或定植性之间没有发现显着相关性。 VI岛与迟发性败血症、X岛与早发性败血症之间可能存在关联，值得进一步研究。结论：NEM316和2603VR菌株的显着之处在于它们的全基因组序列非常相似，表明荚膜位点或其他遗传差异（例如致病性岛）是血清型III菌株引起晚发性疾病倾向的主要决定因素。这项研究支持 GBS 菌株 NEM316 具有四个假定的致病性岛的观点，但没有一个岛对于疾病因果关系是绝对必要的，无论是早发还是晚发败血症。可移动遗传元件是 GBS 分离株的一个共同特征，每种菌株都有其独特的转座子、噬菌体、整合酶和整合质粒。其中大多数不太可能影响分离株的疾病能力。因此，血清型相关的疾病表型可能仅与荚膜位点的差异相关。
Background: Streptococcus agalactiae (Group B Streptococcus; GBS) is a major contributor to obstetric and neonatal bacterial sepsis. Serotype III strains cause the majority of late-onset sepsis and meningitis in babies, and thus appear to have an enhanced invasive capacity compared with the other serotypes that cause disease predominantly in immunocompromised pregnant women. We compared the serotype III and V whole genome sequences, strains NEM316 and 2603VR respectively, in an attempt to identify genetic attributes of strain NEM316 that might explain the propensity of strain NEM316 to cause late-onset disease in babies. Fourteen putative pathogenicity islands were described in the strain NEM316 whole genome sequence. Using PCR- and targeted microarray- strategies, the presence of these islands were assessed in a diverse strain collection including 18 colonizing isolates from healthy pregnant women, and 13 and 8 invasive isolates from infants with early- and late-onset sepsis, respectively.Results: Side-by-side comparison of the strain NEM316 and strain 2603VR genomes revealed that they are extremely similar, with the only major difference being the capsulation loci and mobile genetic elements. PCR and Comparative Genome Hybridization (CGH) were used to define the presence of each island in 39 GBS isolates. Only islands I, VI, XII, and possibly X, met criteria of a true pathogenicity island, but no significant correlation was found between the presence of any of the fourteen islands and whether the strains were invasive or colonizing. Possible associations were seen between the presence of island VI and late-onset sepsis, and island X and early- onset sepsis, which warrant further investigation.Conclusion: The NEM316 and 2603VR strains are remarkable in that their whole genome sequences are so similar, suggesting that the capsulation loci or other genetic differences, such as pathogenicity islands, are the main determinants of the propensity of serotype III strains to cause late-onset disease. This study supports the notion that GBS strain NEM316 has four putative pathogenicity islands, but none is absolutely necessary for disease causation, whether early- or late-onset sepsis. Mobile genetic elements are a common feature of GBS isolates, with each strain having its own peculiar burden of transposons, phages, integrases and integrated plasmids. The majority of these are unlikely to influence the disease capacity of an isolate. Serotype associated disease phenotypes may thus be solely related to differences in the capsulation loci.