Objective: To isolate the cariogenic Streptococcus mutans (Sm) strains and study the therapeutical effect of egg yolk antibody (IgY) of the Sm on dental caries development. Methods: Sm strains were isolated from the children's dental plaque samples. Morphological, biochemical and molecular biological methods were applied to identify the serotype, acid producing and adhesion abilities of isolated Sm strains. After inactivation one of the Sm strains was used as antigen to immune laying hens to collect and extract the specific anti-Sm IgY. The rats were infected with Sm (serotype e). After 16 weeks of infection, all the rats were found developing dental caries. The rats were then randomly divided into two groups. The rats in experimental group were supplied with diet containing anti-Sm IgY while the rats in control group with normal IgY. All rats were sacrificed after another 8 weeks' observation. The degree of caries for each rat was assessed using Keyes' method. Results: We isolated 7 Sm strains from the children's dental plaque samples in the present study. The numbers of serotype c, e, f, k were 3, 2, 0 and 2, respectively. All strains showed similar morphological and biochemical characters as standard UA159 Sm strain, and possessed strong capabilities of acid production and adherence. Interestingly, even the same serotypec strains, such as No.3 and No.7 strains, demonstrated significant difference on acid producing and adherence capabilities. After 16 weeks infection with serotype e strain, the rats' mandibular teeth were apparently decayed, and treatment with specific anti-Sm IgY obviously attenuated the development of caries in the experiment group rats (16.4±2.0) compared with that in the control group rats (30.2±9.3) (P<0.05) determined by Keyes' method. Conclusions: Seven cariogenic Sm strains of different serotypes were isolated, which possesses similar morphology and biochemical characters. Although belonging to the same serotype strains they always show significant difference in acid-producing and adherencec apabilities. Further experiment provides evidences that the serotype e strain could obviously induce caries independently, and employment of specific anti-Sm IgY as passive immunotherapy additive might effectively inhibit the further development of dental caries.
目的： 筛选致龋性变形链球菌并研究其卵黄抗体的抑龋作用，以期为龋齿的防治提供参考。 方法： 从四川省自贡市富顺县某幼儿园5~6岁的儿童龋病患者牙菌斑中分离变形链球菌菌株，并通过形态、生化和分子生物学方法鉴定菌株，分析菌株的血清型、产酸和黏附能力。以灭活变形链球菌为抗原免疫产蛋鸡，提取其鸡蛋特异性卵黄抗体（immunoglobulin Y，IgY）。用e型变形链球菌感染12只SD大鼠，待第16周大鼠形成稳定龋齿后分为两组，实验组大鼠（6只）饲料中添加特异性IgY，对照组大鼠（6只）饲料中添加普通IgY。继续饲喂、观察8周后处死大鼠，使用Keyes计分法评价大鼠的龋损程度。 结果： 从儿童牙菌斑中分离出7株变形链球菌，其中c、e、f、k血清型分别有3、2、0和2株。所有菌株均表现出与UA159标准菌株相似的形态及生化特征，具有较强的产酸和黏附能力；但同为c型的菌株其产酸和黏附能力不同。应用e型变形链球菌感染大鼠16周后，其下颌牙齿均出现龋洞，给予特异性IgY治疗后，实验组大鼠Keyes计分分值[（16.4±2.0）分]显著低于对照组大鼠[（30.2±9.3）分]（P<0.05）。 结论： 本研究筛选得到的7株不同血清型变形链球菌菌株具有相似的形态和生化特性，但在产酸和黏附能力方面，即使是同一血清型也有显著差异；e型变形链球菌具有独立的致龋能力，应用抗变形链球菌IgY作为被动免疫治疗剂可有效抑制龋齿的发展。.
Keywords: Caries inhibition; Immunoglobulin Y; Immunotherapy, passive; Streptococcus mutans.