Development of new method for the treatment of halitosis using molecular biological technique

口腔异味主要与口腔状况有关，起源于食物残渣、口腔粘膜脱屑细胞和口腔内积聚的白细胞等物质中氨基酸的细菌代谢产生的各种产物。这些代谢物包括挥发性硫化物(VSC)、吲哚、臭鼬、胺和氨。在这些化合物中，VSC是引起口腔异味的主要原因。在这项研究中，检查了主诉口臭的患者的特征，并评估了测量口臭的方法的诊断准确性。感官测试显示，55%的受试者没有气味或有轻微的气味。感官评分与其他方法测定的总VSC水平之间存在显著的相关性。口臭阳性组的舌苔量明显高于口臭阴性组，而唾液流率两组间差异无统计学意义。入侵菌株W83和W50产生大量甲硫醇。本研究克隆了牙龈假单胞菌W83的L-methionine-α-deamino-γ-mercaptomethane-lyase(METase)基因。我们还构建了牙龈假单胞菌W83的METase缺陷型突变株。与野生型菌株W83相比，突变体明显减少了L蛋氨酸对甲硫醇的生成，降低了毒力。METase失活可能是抑制口腔异味的有效方法。

Oral malodor is mainly associated with the condition of the oral cavity and is originates from a variety of products produced by the bacterial metabolism of amino acids in materials such as food debris, desquamated cells from oral mucosa and leukocytes that accumulate in the mouth. These metabolites include volatile sulfur compounds (VSC), indole, skatole, amines and ammonia. Of these compounds, VSC are the main cause of oral malodor.In this study, the characteristics of patients complaining of halitosis were examined and the diagnostic accuracy of methods of measuring halitosis was evaluated. The organoleptic test revealed that 55% of the subjects had no or slight odor. There was a significant correlation between the organoleptic score and the total VSC level determined by other methods. The amount of tongue coating was significantly greater in the halitosis-positive group than in the halitosis-negative group, whereas there was no difference in the salivary flow rate between the two groups.The ability of periodontopathic Porphyromonas gingivalis to produce methyl mercaptan was examined. The invasive strain W83 and W50 produced large amounts of methyl mercaptan. We cloned and sequenced the gene encoding L-methionine-α-deamino-γ-mercaptomethane-lyase (METase) from P.gingivalis W83. We also constructed a METase-deficient mutant of P.gingivalis W83. The mutant showed a marked decrease in the formation of methyl mercaptan from L-methionine and decreased virulence compared with the wild-type strain W83. Inactivation of METase may be effective for the inhibition of oral malodor.