Horizontal transmission study of Mutans Streptococci in Children

Objective: To find out horizontal transmission of oral mutans streptococci (MS) in nursery children through analyzing the similarity of MS genotypes. Methods: The study group included 24 nursery children between 3 and 4 years of age. Dental plaque samples were collected with sterile toothpick and cultured on MSB plates for 48h. Individual MS colonies representative of the colonial morphologies were subcultured on TPY plates. These strains were identified to species level biochemically. AP-PCR fingerprinting was preformed after identification. MS isolates from different children with very similar fingerprinting profiles were examined by chromosomal DNA fingerprinting analysis. Results: MS was isolated in oral cavities of 66.7% children, 58.3% in caries-free and 75.0% in caries children. A total of 46 MS isolates from 24 subjects were analyzed by AP-PCR, and 29 different amplitypes were identifyied, 45.8% carried two genotypes. There are 2 genotypes of MS isolated repeatedly among 12 nursery children. Conclusion: The presence of matching genotypes of MS among nursery children suggests horizontal transmission.