Coykendall A L, Freedman M L
Infect Immun. 1981 Apr;32(1):80-5. doi: 10.1128/iai.32.1.80-85.1981.
Streptococcus ferus, which is indigenous to wild rats, is a member of the mutans group of streptococci. We tested its ability to colonize and to cause caries in laboratory rats by comparing two strains of S. ferus with the very cariogenic Streptococcus sobrinus strain 6715. Groups of rats were fed either finely ground mouse chow or a 56% sucrose diet, or they were switched from chow to the sucrose diet. All three strains colonized the mouths of rats regardless of diet. However, the infectants reached higher proportions of the total flora more quickly in the rats consuming sucrose. Similarly, the percentage of the oral flora represented by an infecting organism increased numerically when rats originally fed chow were switched to the sucrose diet. S. ferus formed plaques on the teeth of the rats, but these plaques did not proliferate over smooth tooth surfaces as extensively as did those of S. sobrinus. Although S. ferus colonized and accumulated, it was non-cariogenic in rats fed sucrose compared both with rats fed similarly but infected with S. sobrinus 6715 and with uninfected controls. In vitro measurements suggested the S. ferus produced acid less rapidly than S. sobrinus. Thus, the lack of cariogenicity in S. ferus may result from an inability to form copious plaques on smooth tooth surfaces and from low acid production and, therefore, may represent a natural absence of the pathogenic potential usually inherent in the mutans streptococci.
野生大鼠体内的野生链球菌是变形链球菌属的成员。我们通过将两株野生链球菌与极具致龋性的远缘链球菌6715菌株进行比较，测试了其在实验大鼠口腔中定植和致龋的能力。将大鼠分为几组，分别喂食精细研磨的小鼠饲料、56%的蔗糖饮食，或者先喂食饲料，然后改为蔗糖饮食。无论饮食如何，所有三种菌株都能在大鼠口腔中定植。然而，在食用蔗糖的大鼠中，感染菌在总菌群中所占比例上升得更快。同样，当原本喂食饲料的大鼠改为蔗糖饮食时，感染菌在口腔菌群中所占的百分比在数值上也有所增加。野生链球菌在大鼠牙齿上形成菌斑，但这些菌斑在光滑牙面上的增殖程度不如远缘链球菌。尽管野生链球菌能够定植和聚集，但与同样喂食蔗糖但感染远缘链球菌6715的大鼠以及未感染的对照组相比，它在喂食蔗糖的大鼠中不具有致龋性。体外测量表明，野生链球菌产酸速度比远缘链球菌慢。因此，野生链球菌缺乏致龋性可能是由于它无法在光滑牙面上形成大量菌斑以及产酸量低，所以可能代表了变形链球菌通常固有的致病潜力的天然缺失。
