Demonstration Of Altered Colony Morphology Of Mutans Streptococci and their Role in Cariogenicity

Different colonial variants of Mutans Streptococci are observed on sucrose containing media such as Mitis Salivarius Agar (MSA). Variation in colony morphology seems to be related to synthesizing cell surface Demonstration Of Altered Colony Morphology Of Mutans Streptococci ... ٢٥ materials, namely; the glucan capsule. Saliva samples from 100 subjects of both sexes aged from 7-52 years old were enrolled. Mutans Streptococci (MS) with various colony morphology and various degrees of adherence were demonstrated in the present study. The incidence of rough colony morphology was shown to be 38% of the local isolates, in addition to that 56% of the saliva samples harbored one strain of Mutans Streptococci, 40% of them had more than one and 4% were negative. The mean DMFT/dmft (Decayed teeth + Missed teeth + Filled teeth) value was 4, 5 respectively. The mean decayed teeth for samples with one strain was 2.8 while samples with two or more strains had an average of decayed teeth 3.6. which indicates that subjects harboring more than one strain have a higher incidence of dental caries than those with one strain. Eight Streptococcus mutans isolates (Mannitol and 2,3,5Triphenyltetrazolium Chloride positive.) showed various degrees of adherence which is known to be an important virulence factor of this microorganism. Introduction The genus Streptococcus (phylum: Firmicutes, Order: Bacillales, and Family: Streptococcacae) can be divided into seven groups, Pyogenic, Sanguis, Mitis, Mutans, Salivarius, Anginosus, and Bovis group. The cariogenic organism Streptococcus mutans have been divided into serotypes. They have subsequently been elevated to species status and now comprise the "mutans group" of oral streptococci (1). An important characteristic of this type is the formation of zoogleal colonies on sucrose agar; presumably, this is caused by large amounts of insoluble dextranlike polysaccharides (glucan). Its glucan capsule is synthesized by a class of extracellular and cell-wall associated enzymes called glucosyltransferases and fructosyltransferases. The action of these enzymes on dietary sucrose creates a branched, insoluble glucan matrix that specifically interacts with the tooth surface and with receptors on the cells. Subsequent formation of acids from intracellular glycogen stores in Streptococcus mutans and other organisms leads to formation of dental caries (1). Cariogenic bacteria is known to synthesize two types of glucan; water-soluble and water-insoluble glucans, through the latter, a more tenacious attachment to tooth surfaces is achieved. Extracellular dextrans (glucans) produced from sucrose by microorganisms found in dental plaques appear to play at least two roles in the formation of dental caries; first, the cariogenic potential of these microorganisms is dependent on the production of dextran which can initiate cell aggregation and plaque formation (2-5). Second, glucans have been theorized to be important as a part of the stable intracellular plaque matrix (2, 6, 7). Different colonial variants of this organism are observed occasionally on sucrosecontaining media such as Mitis Salivarius agar. Such co-