牙龈卟啉菌及其胶原酶基因遗传多样性的研究

目的 分析牙龈卟啉单胞菌细菌基因型及其重要毒力因子胶原酶基因PrtC的遗传异质性，了解细菌遗传变异与其致病性的相关性。方法 对从不同牙周炎患者口腔中分离出的牙龈卟啉菌进行DNA指纹分析，参考菌株为PgATCC33277。通过PCR反应，检测临床菌株中是否存在特异性的胶原酶基因片段（548bp）。并通过酶切鉴定和DNA序列分析，了解PrtC基因遗传多样性的变化。结果 80株牙龈卟啉菌共获得7种基因型（Ⅰ-Ⅶ）。所有24株临床菌株和参考菌株PgATCC3327中均扩增出特异性的胶原酶基因片段。对照菌株中没有得到相应的产物。4株细菌的序列分析结果与国外的报道相比较，发现一些基因序列存在差异，出现6个核苷酸碱基缺失。结论 临床分离的牙龄卟啉菌中可检测到多种基因型，且具有个体差异，这些菌株具有合成胶原酶的能力，不同菌株胶原酶基因之间存在遗传异质性的变化。

Polymerase chain reaction analysis of the clonality of Porphyromonas gingivalis and collagenase gene

OBJECTIVE: To investigate the genotypic characterization of Porphyromonas gingivalis (Pg) and the heterogeneity of a potential virulence factor-PrtC. METHODS: Arbitrarily primed polymerase chain reaction (AP-PCR) was applied to 80 Pg strains isolated from 24 unrelated Chinese periodontitis patients. PCR reaction was used to detect a fragment of the collagenase gene (PrtC gene). To evaluate the sequence heterogeneity of the Pg PrtC genes, sequence analysis of four PrtC gene of clinical isolates was performed. RESULTS: Random primer OPA-05 and OPA-17 distinguished 7 AP-PCR profiles (I through VII). The majority of the strains belonged to type VII which accounted for 25.8%. A 548bp fragment of PrtC gene was detected from 24 clinical strains. The PCR products were verified by the restriction endonucleases PstI and PvuI. Sequence analysis showed 4 PrtC genes were heterogeneous in their nucleotide composition and differed from reference strain Pg 53977. CONCLUSIONS: The results demonstrated genetic diversity existed among these clinical strains isolated from Chinese periodontitis patients and the PrtC genes are heterogeneous in their nucleotide sequence.