The determination of the composition of the microbial community in the oral cavity is usually based on cultivation methods; however, nearly half of the bacteria in the saliva and the dental plaque are not cultivable. In this study, we evaluated the difference in oral microbial diversity between children with severe early-childhood caries (S-ECC) and caries-free (CF) controls by means of a cultivation-independent approach called denaturing gradient gel electrophoresis (DGGE). Pooled dental plaque samples were collected from 20 children aged 2 to 8 years. Total microbial genomic DNA was isolated from those subjects, and a portion of the 16S rRNA gene locus was PCR amplified by using universal primers. We observed that the mean species richness of the bacterial population was greater in the CF children (n = 12) (42 ± 3.7) than in the S-ECC children (n = 8) (35 ± 4.3); the difference was statistically significant (P = 0.005). The overall diversity of plaque samples as measured by the Shannon index was 3.5 for the S-ECC group and 3.7 for the CF group (P = 0.004). Differences in DGGE profiles were distinguished on the basis of a cluster analysis. Sequence analysis of excised DGGE bands consisted of 2.7 phylotypes, on average. After adjusting for the number of observed bands, we estimated that the S-ECC group exhibited 94.5 total phylotypes and that the CF group exhibited 113.4. These results suggest that the microbial diversity and complexity of the microbial biota in dental plaque are significantly less in S-ECC children than in CF children.
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机译：口腔中微生物群落组成的确定通常基于培养方法。但是，唾液和牙菌斑中几乎有一半细菌无法培养。在这项研究中，我们通过称为变性梯度凝胶电泳（DGGE）的与培养无关的方法，评估了患有严重早期儿童龋病（S-ECC）和无龋齿（CF）对照的儿童之间口腔微生物多样性的差异。从20名2至8岁的儿童中收集牙菌斑样本。从这些受试者中分离出总的微生物基因组DNA，并使用通用引物对16S rRNA基因位点的一部分进行PCR扩增。我们观察到，CF儿童（ n = 12）（42±3.7）的细菌种群平均物种丰富度高于S-ECC儿童（ n = 8）（35±4.3）;差异具有统计学意义（ P = 0.005）。通过香农指数测量的斑块样品的总体多样性对于S-ECC组为3.5，对于CF组为3.7（ P = 0.004）。 DGGE配置文件中的差异基于聚类分析得以区分。切除的DGGE带的序列分析平均包含2.7种系统型。调整观察到的条带数量后，我们估计S-ECC组展示了94.5个总系统型，CF组展示了113.4个。这些结果表明，S-ECC患儿的牙菌斑中微生物群的微生物多样性和复杂性明显低于CF患儿。
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