A Study On The Relationship Between Transmission Of Mutans Streptococci From Mothers To Children And Its Virulence Factors

Dental caries harmed the health of human oral cavity, it is an infectious, transmissible disease in which members of the mutans streptococci (MS) have been considered as major etiological agents of human dental caries. The tooth is highly susceptible to caries in the first few years after eruption. This period of increased caries susceptibility has been explained as poor maturation of the enamel surface. In children, the presence and level of the micro-organisms correlates to the caries incidence in the primary dentition as well as in the permanent dentition during this first critical years. All studies to determine what factors effecting the MS transmission and colonization will give light to preventing or delaying the transmission of MS to child.Many studies have identified the sources of the bacteria among humans, but it was not clear that what factors effecting the MS transmission and colonization. MS strains show high genotypical heterogeneities, variations in some virulence factors of MS isolates were associated with their ability to infect the host and to form biofilm. However the problem that whith the virulencefactors were related to its ability to transmission remains unanswered.The purpose of this study was to observe the possible relationship between MS transmission and its virulence factors within some related individuals (mother-child pairs). In the present investigation, first 50 pairs mother-child were tested for the presence of MS and 200 strains were isolated from 20 pair MS-infective mother-child. Then the transmission between 16 mothers and their young children was determinated and 49 transmitted strains and 51 nontransmitted strains were detected by AP-PCR genotyping. On basis of these, the properties of mutacin production, initial adherence and sucrose-dependant adherence were compared to observe the possible relations between MS virulence factors and its transmission.Results:I. The results of experience to test the mutacin production and the prevalence of mutA showed:1. MutAI only was detected among nontransmitted strains, suggested a reduced possibility of transmission if an isolate carried the gene.2. Isolates representing different genotype from unrelated subjects show heterogeneity in mutacin production, did not observe any superiority of mutAI-camed strains over other strains of mothers.3. The low frequency of detection of mutA genes suggested there may be a family of mutacins, and some new kinds of them remain unknown, suggesting the need for further studies to purify them and to identify the genes responsible for their production.II. The results of experience to test the initial adherence properties showed:1. Nontransmitted strains own a poorer adherence property to SHA thantransmitted strains.2. The difference maybe related to the RFLP-types of A-region and PV-region in its surface protein.III. The results of experience to test the sucrose-dependant adherence properties showed that difference was observed neither in adherence to a smooth glass surface nor in mRNA expression of the gtf genes indicating on correlation between MS transmission and its sucrose-dependant adherence properties.Conclusion: The results of this study suggest that MS transmission was related to its properties of mutacin production and the initial adherence. An isolate carried mutAI gene was less easily to transmission, while a strain owning a poorer initial adherence property indicated a greater possibility to transmission.