Streptococcus agalactiae (group B Streptococcus, GBS) represents a leading cause of invasive bacterial infections in newborns and is also responsible for diseases in older and immunocompromised adults. Prophages represent an important factor contributing to the genome plasticity and evolution of new strains. In the present study, prophage content was analyzed in human GBS isolates. Thirty-seven prophages were identified in genomes of 20 representative sequenced strains. On the basis of the sequence comparison, we divided the prophages into eight groups named A–H. This division also corresponded to the clustering of phage integrase, even though several different integration sites were observed in some relative prophages. Next, PCR method was used for detection of the prophages in 123 GBS strains from adult hospitalized patients and from pregnancy screening. At least one prophage was present in 105 isolates (85%). The highest prevalence was observed for prophage group A (71%) and satellite prophage group B (62%). Other groups were detected infrequently (1–6%). Prophage distribution did not differ between clinical and screening strains, but it was unevenly distributed in MLST (multi locus sequence typing) sequence types. High content of full-length and satellite prophages detected in present study implies that prophages could be beneficial for the host bacterium and could contribute to evolution of more adapted strains.

中文翻译：

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临床和携带者无乳链球菌的特性和对噬菌体变异性的噬菌体贡献

无乳链球菌（B链球菌，GBS组）代表了新生儿侵入性细菌感染的主要原因，并且还引起了老年人和免疫功能低下的成年人的疾病。噬菌体代表了有助于基因组可塑性和新菌株进化的重要因素。在本研究中，分析了人类GBS分离物中的噬菌体含量。在20个代表性测序菌株的基因组中鉴定出37个噬菌体。在序列比较的基础上，我们将这些预言分为8个名为A–H的组。该划分也对应于噬菌体整合酶的聚类，即使在某些相对的噬菌体中观察到了几个不同的整合位点。接下来，PCR方法用于检测来自成人住院患者和妊娠筛查的123 GBS菌株中的噬菌体。105个分离株（85％）中至少存在一个噬菌体。A组（71％）和B组（62％）卫星传播的患病率最高。很少发现其他组（1-6％）。噬菌体的分布在临床菌株和筛选菌株之间没有差异，但是在MLST（多基因座序列分型）序列类型中分布不均。在本研究中检测到的全长和卫星噬菌体的高含量意味着，噬菌体可能对宿主细菌有益，并且可能有助于适应性更强的菌株的进化。但它在MLST（多基因座序列分型）序列类型中分布不均。在本研究中检测到的全长和卫星噬菌体的高含量意味着，噬菌体可能对宿主细菌有益，并且可能有助于适应性更强的菌株的进化。但它在MLST（多基因座序列分型）序列类型中分布不均。在本研究中检测到的全长和卫星噬菌体的高含量意味着，噬菌体可能对宿主细菌有益，并且可能有助于适应性更强的菌株的进化。