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【medical-news】JCM：羊水中发现不可培养的细菌z
Uncultivated Bacteria as Etiologic Agents of Intra-Amniotic Inflammation Leading to Preterm Birth
Yiping W. Han,1,2* Tao Shen,1 Peter Chung,1 Irina A. Buhimschi,3 and Catalin S. Buhimschi3
Department of Periodontics, Case Western Reserve University School of Dental Medicine, Cleveland, Ohio 44106,1 Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106,2 Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University, New Haven, Connecticut 065203
Intra-amniotic infection and inflammation are major causes of preterm birth (PT. However, intra-amniotic inflammation is often detected in the absence of infection. This may partly be due to the culturing methods employed in hospital laboratories, which are unable to detect the uncultivated species. In this study, intra-amniotic microbial infections associated with PTB were examined by both culture and 16S rRNA-based culture-independent methods and were corroborated by the presence of intra-amniotic inflammation. Amniotic fluid (AF) specimens from 46 pregnancies complicated by PTB and 16 asymptomatic women were analyzed. No bacterial DNA was amplified in AF collected from the asymptomatic women. Among the 46 samples associated with PTB, bacterial DNA was amplified from all (16/16) of the culture-positive samples and 17% (5/30) of the culture-negative samples. In the culture-positive group, additional species were detected in more than half (9/16) of the cases by PCR and clone analysis. Altogether, approximately two- thirds of the species detected by the culture-independent methods were not isolated by culture. They included both uncultivated and difficult-to-cultivate species, such as Fusobacterium nucleatum, Leptotrichia (Sneathia) spp., a Bergeyella sp., a Peptostreptococcus sp., Bacteroides spp., and a species of the order Clostridiales. To examine intra-amniotic inflammation, an AF proteomic fingerprint (mass-restricted score) was determined by surface-enhanced laser desorption ionization-time-of-flight mass spectrometry. Inflammation was detected in all five samples which were culture negative but PCR positive. Women who were PCR positive more often had elevated interleukin-6 levels in their AF, histological chorioamnionitis, and funisitis and delivered neonates with early-onset neonatal sepsis. Previously unrecognized, uncultivated, or difficult-to-cultivate species may play a key role in the initiation of PTB.
来自凯斯西部保留地大学和耶鲁大学的科学家在理解为何一些孕妇的子宫内部会遭遇无任何感染迹象的炎症问题上有了显著的进展。
利用基因克隆技术，科学家发现存在于患羊膜内炎症的妇女体内的大约60%的细菌被传统的培养测试漏掉了，后者被认为是发现细菌感染的金标准。
这些发现发表在了《临床微生物学杂志》1月号上。
这组科学家利用新的DNA方法追踪细菌的存在，从而首次发现了羊膜内感染的微生物物种的一份详尽名单。为了增加准确性，这组科学家使用了多种分析手段的综合，包括羊水的蛋白质组学结果以及对胎盘的组织学分析，从而证实这种感染和炎症。
凯斯西部保留地大学的牙科医学副教授、该研究的主要作者Yiping Han说，羊膜内炎症已知会导致不到32周的胎儿的自发早产。该研究对46名妇女进行了研究，其中44名妇女经历过早产。Han 此前进行了多个研究项目，检查了口腔细菌和早产之间的联系。
在这项研究中，科学家对来自有早产体征或症状的怀孕妇女的羊水细菌浓度和对照组的没有这类迹象且足月分娩的16名妇女的羊水细菌浓度进行了比较。对照组的羊水来自用于遗传筛查的羊水穿刺或者检查胎儿肺部成熟的分析，甚至DNA方法也没有显示出其中有细菌的迹象。
“由于培养没有发现羊水中的全部细菌，这要求使用新的检测方法，”Han说。“同样重要的是发现哪种细菌造成了导致早产的感染和炎症，从而在这个病理生理学连锁事件的早期使用抗生素。”
利用新的检测过程——该过程为了识别16SrRNA细菌基因序列，扩增了该基因并把它克隆——除了可以发现细菌培养能发现的细菌，这组科学家还有能力发现一些细菌培养无法发现的有害细菌，其中一些细菌此前没有和早产联系起来。
“通过利用基于16s rRNA基因的聚合酶链式反应（PCR）和之后的克隆分析，我们可以确定羊膜内细菌感染和早产发作之间的特征和真正的关系，”Han说。
这组科学家还发现不仅仅是样本中的一种细菌导致了炎症，而是大量的不同种类的细菌，“未被发现的、无法培养的或很难培养的细菌物种可能在导致自发早产方面扮演了一个关键的角色，”Han说。
这些细菌或者通过生殖道到达胎盘，或者通过血液到达胎盘。Han怀疑其中一些细菌源于口腔，口腔中存在成百上千种细菌。这些口腔细菌中的一种是具核梭杆菌（Fusobacterium nucleatum ），它在口腔中普遍存在。然而，一旦它进入了血流中，它就和一些健康问题有了关联。 其中的因果关系还值得商榷。 [标签:content1][标签:content2]
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作者:admin@医学,生命科学 2011-08-12 02:16
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