Comparison of mutans streptococcal strains of father, mother, and child in Indian families using chromosomal DNA fingerprinting

Abstract

INTRODUCTION: It is now understood and accepted that there is a direct transmission of mutans streptococci (MS) from the mother to the child. There is also a direct correlation between the levels of MS in the mother and the caries status of the child. Advanced technologies in molecular biology like chromosomal DNA fingerprinting have established beyond doubt that the mother and the child bear similar strains of MS. Aim: A study was designed with the aim of comparing the MS strains between the father, mother and the child in Indian families. Materials and methods: A group of 20 Indian families comprising of the father, mother and child were selected and divided into caries free and caries active groups. Mixed salivary samples were collected from the individuals and were cultured for the growth of Mutans streptococci. The colonies were counted on a colony counter and a comparison was made between the mutans streptococcal counts of the mother and the caries status of the child. Further, the genotypes of the father, mother and the child were isolated and compared using the technique of chromosomal DNA fingerprinting. Following electrophoresis, the band pattern obtained was compared for similarities or differences. The results of the same were tabulated and evaluated statistically. Results: When the colony counts of the mother (in CFU/ml) were compared with the 'dft' status of the child, a positive correlation was seen in group II. Intergroup comparison using the unpaired T test was statistically significant. Electrophoretic analysis of the chromosomal DNA on the agarose gels revealed identical band patterns in 13 mother-child pairs, which was statistically significant. Three of the father-child pairs showed identical band patterns, which was statistically significant. Intergroup comparison using Chi-square test was not statistically significant. Conclusion: One may conclude that irrespective of the caries status of the child, majority of the mother child pairs share identical strains of MS and hence the mother is the primary source of infection. However, in children with a high dft, the father may also play an important role in the acquisition and transmission of MS.